Understanding Lipids and Healthy Fats

Hi everyone, today we will cover Chapter 5, where we will discuss the lipid family, which includes fats, oils, phospholipids, and sterols. Please read through the following learning objectives, and then lecture will begin. There are two sides of the coin for fat. They are valuable and necessary for health. on one side, but they also have the potential to harm health on the other side. Ultimately, we must find a balance by moderating fat intake and, probably more importantly, the types of fat that we choose. Fat plays many roles in the body and also in food. Fat provides fat-soluble vitamins, which are A, D, E, and K, essential fatty acids, which have to be obtained through the diet, Fat also helps carry fat-soluble vitamins through the lymphatic system for absorption. It's our chief form and long-term energy storage. It serves as an emergency fuel source, a material for cell membranes. It can be converted to other compounds when needed. It is used for cushioning and protection of our organs. It offers insulation for extreme temperatures. and it fuels muscle work at low to moderate activity. Fat also plays a role in satiety or the feeling of fullness. It helps slow the transit of food through the GI tract and also helps trigger a nerve signal to the brain to delay hunger. We have to be careful, though, because taste can easily override these signals, and it's very easy to overeat fatty foods. And last but not least, fat also helps contribute to the taste and smell of food. which also kind of plays into why taste can easily override some of our satiety signals. There are three classes of lipids. Triglycerides, which represent about 95% of the lipids or fat found in food in the body. Phospholipids, which are similar to triglycerides, but have a phosphorus-containing acid in place of one fatty acid. And sterols, of which cholesterol is the most common. Now we will start looking at each class of lipids, starting with triglycerides, the major form of fat found in the food and the body. Fatty acids are rarely found free in the body. They are instead packaged as triglycerides. However, tissues in the body can easily disassemble and assemble triglycerides when needed. Your body is constantly disassembling and assembling them. Here you can see how a triglyceride is formed. The name pretty much says it all. Three fatty acids are attached to a water soluble glycerol molecule backbone. Glycerol is a derivative of carbohydrate and composed of three carbons. While the glycerol backbone remains the same, fatty acids can differ from one another. Chain length can vary as can saturation. Triglycerides typically contain various types of fatty acids. Chain lengths can vary from anywhere from 4 to 24 carbons, with 18 being the most common. Fatty acids are chains of carbon atoms with hydrogen atoms attached. They have an acid group at one end, hence the name fatty acid, and a methyl group at the other end. The methyl group is alkaline derived from methane. It contains one carbon atom bonded to three hydrogen atoms. Fatty acids differ in chain length or how many carbons they have. Long chain fatty acids are 12 to 24 carbons long and are commonly found in meat, fish, and nuts and seeds and their oils. Medium chain triglycerides are six to ten carbons long. Coconut and palm oil contain some medium chain triglycerides, and medium chain triglycerides are also used clinically for fat malabsorption disorders. Lastly, short chain fatty acids have less than six carbons, and they are most commonly found in dairy products, but only in small amounts. Most of our Short chain fatty acids are actually produced by our friendly gut bacteria. They ferment fibers to produce. short chain fatty acids, and these short chain fatty acids are then a fuel source for the cells of our colon and also helpful for human health. As mentioned, triglycerides are composed of different types of fatty acids. They can be a mixture of saturated and or unsaturated. Saturated refers to how many hydrogen atoms the fatty acid chain can hold. A saturated fatty acid is filled to capacity with hydrogen atoms and has no double bonds. Unsaturated fatty acids include polyunsaturated and monounsaturated. Polyunsaturated fatty acids have two or more points of unsaturation, meaning they are missing two or more hydrogens and have two or more double bonds. Monounsaturated fatty acids only have one point of unsaturation and consequently one double bond. Most of the triglycerides you eat in food have a mix of saturated and unsaturated fatty acids. Here are some examples of different fatty acids. Stearic acid is a saturated fatty acid. You can see that the carbons are completely saturated with hydrogen atoms. Oleic acid is an example of a monounsaturated fatty acid found in olives and avocado. Linolenic acid and linoleic acid are both essential fatty acids that are polyunsaturated. The 3 in omega-3 represents where the first double bond is located from the methyl end. Likewise for omega-6. The last figure shows that a triglyceride is most often a mixture of different types of fatty acid. This one in the right lower corner has one saturated, one monounsaturated, and one polyunsaturated. How saturated a fatty acid is determines its melting point, which can also determine its healthfulness. Unsaturated fats are liquid at room temperature and are generally healthier. Conversely, saturated and trans fats are solid at room temperature and less healthy. If it is recommended to limit solid or saturated fats and use mono or polyunsaturated instead, you can gauge healthfulness by how hard something is at room temperature. Stability also differs. Unsaturated fats are more vulnerable to oxidation and spoilage or rancidity. especially cold-pressed and unrefined oils. It is best to refrigerate these oils. Some companies add antioxidant compounds to protect against spoilage. Keep in mind that when an oil or when heat is used to extract oil and oils are refined, vitamins, minerals, and phytochemicals are also lost. Here is a little game where you can guess the type of fat in different oils and foods. So olive oil is primarily monounsaturated. Soybean is polyunsaturated. Ground beef is mostly saturated. Pecans, monounsaturated. Walnuts, polyunsaturated, a good source of omega-3s. Almonds, monounsaturated. Cheese. saturated, coconut, saturated, avocados, monounsaturated, flax seeds, polyunsaturated, an excellent source of omega-3s, butter, saturated, and fish, polyunsaturated. Some fish like flax seeds and walnuts are also a really good source of omega-3s. This figure shows the fatty acid composition of common food fats. As we talked about earlier, most fats are a mixture of saturated, monounsaturated, and polyunsaturated fatty acids, which you can see here in this chart. The arrows to the right hand side represent whether those fats should be lower in the diet or higher in the diet when you're thinking about your total fat content. So for example, we want to limit saturated fats and we want to limit vegetable oils that are high in omega-6s, but we need more omega-3s and having more monounsaturated fats that make up more of our total fat intake would be desirable. And this chart just gives you the fatty acid profile of different nuts and seeds. And you can see that they're also a mixture of saturated, although most are low in saturated fats, and then polyunsaturated and monounsaturated. Now I want to discuss the other two classes of lipids, which are phospholipids and sterols. As mentioned, phospholipids are similar to triglycerides, but they only have two fatty acids. Their third molecule is a phosphorus molecule. This is unique because this phosphorus molecule makes them soluble in both water and fat. At the same time, it has the ability to act as an emulsifier by keeping fats dispersed in water. Lecithin is a good example. This phospholipid emulsifies fats in foods. For example, oil and vinegar will separate with vinegar on the bottom and oil on the top. But what about mayonnaise? It is primarily oil and vinegar, but with the help of lecithin found in egg yolks, which is an ingredient in mayonnaise, the fat is emulsified so that it is dispersed, stable, and spreadable. Lecithin is also produced by the body and present in all cell membranes. Phospholipids like to arrange themselves into two parallel layers with the hydrophilic glycerol phosphate group facing outwards and the hydrophobic or triglyceride part being forced inwards away from the water. This forms a protective layer in all cell membranes called the lipid bilayer. This bilayer is critical to cell functioning. It lets certain molecules in and keep certain molecules out. out. So here is just a little more on lecithin. Phospholipids are also found in the form of lecithin, which is found naturally in egg yolks, soybeans, sunflower seeds, and wheat germ. As mentioned in food, lecithin emulsifies fat and contributes to a stable and creamy product. You can see the chemical makeup of lecithin on the bottom. There's the two fatty acids and then the phosphate group, which makes it soluble in both water and fat. The last class of lipids is sterols. Cholesterol is an example. And cholesterol has a complicated structure with rings of carbon with side chains of carbon, hydrogen, and oxygen. While we often associate cholesterol with heart disease, and rightly so because it forms plaque that clogs arteries, it also has important roles such as making emulsifiers in bile, forming the structure for cell membranes, and manufacturing vitamin D which is another sterol. It also plays a role in the formation of hormones. That said, cholesterol is not essential. Our body can make what it needs. Cholesterol in the diet is only from animal products but sterols also exist in plants and confer health benefits. Even though they resemble cholesterol, they actually inhibit absorption, lowering blood levels. You can find them in nuts, seeds, legumes, and fruits and vegetables in small amounts, and then some are also added to foods to impart that benefit. However, most of the research shows that you need to have at least two grams of these plant sterols to make significant difference in cholesterol levels and some of the foods that plant sterols are added to are maybe not the most health promoting foods that you would want to add to your diet like margarine for example or orange juice or granola bars but if you already eat these items in your diet and you switch to something that does have sterols then perhaps it might impart some kind of benefit As a reminder, an enzyme in saliva leads to a small amount of digestion. Infants actually have an enzyme secreted by the tongue to help digest milk fat, but this is pretty much inactive in adults. There is little digestion of fat in the stomach as fat droplets separate from water and the stomach does not have enough churning power to disperse the fat. But as fat reaches the small intestine, it can now be Emulsified. This happens with the help of bile, which is secreted by the gallbladder, and it's alerted by a hormone to do so. And then it's secreted in the top portion of the small intestine, which is the duodenum. As you can see, bile, or as we've talked about, bile, actually you'll see that on the next slide, sorry. Bile, also like an emulsifier in food, or phospholipid, attracts bile. both water and fat. Bile suspends fat droplets within watery fluids so that enzymes from the pancreas can then break them down into smaller components. These enzymes split fatty acids from their glycerol backbone. The result is free fatty acids, phospholipids, and monoglycerides, which is still that glycerol backbone with just one fatty acid attached. They all cling together in a ball surrounded by the bile to remain emulsified. Now here you can see how bile emulsifies fat. In the stomach, you can see that the fat is separated from the water so that the enzymes don't have access to the fat to be able to break them down and get them ready for absorption. But when fat enters the small intestine, just the right amount of bile is secreted, and that bile is water and fat soluble, so it more or less kind of pulls the droplets of fat down and suspends them in the watery fluid in the small intestine. And then after emulsification, more fat is exposed to the enzymes, and fat digestion proceeds along pretty efficiently. Now that the fatty acids are split from glycerol and the fatty acids and monoglycerides are surrounded by bile, they are ready for absorption. But they have one more barrier to address. And this is the mucosal lining of the small intestine. The lining is watery and they need to get past this layer to enter the cells that line the small intestine. So bile comes to the rescue again. It kind of acts like a shuttle and transports fat across the mucosal layer where the cells of the villi are. Fat is then extracted and bile is either absorbed and reused by the body or it is carried out with feces along with soluble fiber. Once cleaved by enzymes, glycerol and shorter chain fatty acids freely pass into the bloodstream and eventually make their way to the liver. Larger fatty acids need more assistance, though. They still float in water, and they need a way to stay dispersed. The GI tract absorbs about 98% of triglycerides from a meal, making digestion and absorption very efficient. But the process takes time, and most fat is not excreted. That means we're really good at storing fatty acids if we don't need to use them for energy. As mentioned, larger lipids need more assistance in order to be absorbed and packaged for transport. Larger lipids, like free fatty acids, combine with bile to form micelles. Now they are water-soluble enough to diffuse into intestinal cells. Remember how triglycerides are always being assembled and disassembled in the body? Well, now triglycerides are reformed in the intestinal cells. where they then combine with proteins, cholesterol, and phospholipids to form a chylomicron. A chylomicron is one type of lipoprotein. Lipoproteins are used to transport triglycerides. They allow fats to ride as passengers through the blood. We will discuss other types of lipoproteins soon. Chylomicrons can now enter the lymphatic system through the lymph vessels in the villi where they will eventually be routed to the liver, then to the blood, and delivered to cells of the body. This slide gives you a nice summary of lipid digestion and absorption. And at the bottom right-hand corner, you'll also see that chylomicron that is there to help transport triglycerides from the digestive system. So here is a summary of all of the types of lipoproteins in the body. So we just talked about the chylomicrons. They're made in the small intestine and they're a result from triglyceride digestion. That TG means triglyceride. They are absorbed into the lymph after digestion. They're very rich in triglycerides and they're the largest and least dense. So as the chylomicron travels through the bloodstream, cells in the body remove lipids as they pass through. And either they'll use them for energy or they will store them as fat. Now, liver cells then remove the chylomicron remnants from the blood and form new triglycerides in the liver. And this is where we get VLDL, which is very low density lipoprotein. These lipoproteins are secreted into the blood. And they're still pretty rich in triglycerides and not very dense. And their job is to also transport triglycerides from the liver and deliver them to cells of the body. Now we have LDL, which is low density lipoprotein, which is made in the liver after VLDL loses most of its triglycerides. So now the proportion of cholesterol is increasing. And this LDL is what we call. bad cholesterol. It's also secreted into the blood and since it's lost most of its triglycerides, it's very rich in cholesterol and very large in light. Its job is to circulate and deliver triglyceride, cholesterol, and phospholipids to the cells of the body. But most of what it's doing is delivering cholesterol because it's very rich in cholesterol. Lastly, we have HDL, which is high density lipoprotein. It's also made in the liver and maybe small amounts in the small intestine. And it's what we call good cholesterol. It's secreted into the blood, and it's very rich in protein and small and dense. And its job is to kind of act like a scavenger. It picks up cholesterol from cells and then takes that cholesterol to the liver for recycling or disposal. So it helps lower cholesterol levels and manage them in a positive way. And here you can see each of the different lipoproteins and the density. The density of a lipoprotein is determined by its lipid to protein ratio. All lipoproteins contain protein, cholesterol, phospholipids, and triglycerides in varying amounts. And LDL has a higher ratio of lipid to protein, about 80% lipid and 20% protein, and it's especially high in cholesterol. And HDL, on the other hand, has more protein relative to its lipid content and about equal parts of lipid and protein. So this slide here gives you a nice summary of how lipoproteins are made and also lipid transport throughout the body. Lipoprotein concentrations in the blood have a connection to health. High levels of LDL, which is our bad cholesterol, is associated with increased risk of heart disease, whereas higher HDL is associated with lower risk. Several lifestyle factors raise or lower LDL, and HDL. This includes weight management, dietary fat, soluble fiber, exercise, and alcohol consumption. As we've discussed, any type of food or macronutrient eaten in excess will be stored as fat. While this might be a detriment today, it was a survival mechanism for our ancestors who relied on fat stores during periods of famine. When food was plentiful, fat was stored to prepare for limited food availability. Not all cells are designed to store fat, or at least not a lot. However, adipose tissue specializes in fat storage. Think of fat cells like a balloon that can keep on expanding in size. The more fat they store, the larger they grow. In addition to fat storage, they also secrete hormones that regulate appetite. The body reserves most fat stores and uses them when needed. The body's natural tendency is to conserve them though in case. They're needed in times of emergencies or increased or prolonged physical activity. Triglycerides, as we mentioned, are transported by chylomicrons to fat depots, such as under the skin, around the abdomen, breasts, hips, etc. They are stored for future energy needs, such as when fuel sources from food are low, then fat stores are called upon for energy and fuel. As discussed, when there is plenty of fuel available, the body can convert excess carbohydrate to fat. But remember, this is not energy efficient as it requires several steps. The body also has enzymes to convert excess protein to fat or to glucose, but these are even less efficient. This doesn't mean that excess calories from protein and carbohydrates don't lead to fat storage. They do. And mainly from sweets and meats, but fat storage from dietary fat is very efficient, requiring much fewer steps. Now, why isn't glucose the major form of stored energy? We know that it's critical to cells and very efficient as an energy source for cells, but it's also very bulky because glycogen holds water, about three grams per gram of carbohydrate. and the body just can't handle storing that much water. Fat, on the other hand, is very compact, and it's packed tightly together without water. And remember, it provides nearly twice the amount of energy of carbohydrate or protein. When the body needs to use fat for energy, it dismantles triglycerides in the fat cells and releases fatty acid into the blood. Cells further break them down into fragments and combine with fragments from glucose, releasing more energy, carbon dioxide, and water. Your fat stores are actually fueling about 80 to 90% of your body's needs when you're at rest or when food from fuel is low. And they're also a good fuel source during low to moderate activity. And the more trained a person becomes... the more able they are to spare their glycogen and rely on fat for energy. But you have to be at a low to moderate rate. So think like an endurance event where you're going long periods of time. Now, to be able to lose fat, like say you're trying to lose weight and you want to lose body fat, you need to create a demand. So that might be restricting food intake or... increasing energy or better yet both. And it's important to know that your fat cells do not shrink in numbers, but they shrink in size. Remember, they're like a balloon. They can get bigger and bigger and bigger, but the number of fat cells that you have would be more, you know, dependent on genetics. Okay, on to recommendations for lipid intake or fat intake. We need some fat in the diet, otherwise we risk not getting enough essential fatty acids and fat-soluble vitamins. And, of course, not getting enough fat-soluble vitamins can lead to vitamin deficiencies. Too little fat in the diet can also lead to hormonal problems along with decreased immunity and thyroid function. Dry, rough skin may also be present, perhaps, from inadequate vitamin A. DRIs recommend that 20 to 35% of total calories come from fat. This is also true for athletes. Athletes rely on fat to fuel activity, their fat stores at least. Fat helps achieve their higher calorie needs. So restricting fat isn't necessarily ideal for them for performance. Lower percentages of fat in the diet can be helpful for treating and reversing chronic disease, but this should really be evaluated on a case-by-case basis with a healthcare professional like a dietician or a doctor, for example. We will look at specifics for different fatty acids next, but in general, we want to lower saturated fat intake and focus on omega-3s and monounsaturated fats as our primary source of fats in the diet. Current fat intake in the US averages about 34% total calories from fat and 11 to 12% total calories from saturated fat. This table here outlines lipid recommendations for healthy people. We already talked about total fat, which should be 20 to 35 percent of total calories. Saturated fat is generally 10 percent or less of total calories. However, the American Heart Association recommends to be even stricter with saturated fat if you have high blood cholesterol. Trans fat should be as little as possible. And then you can see the recommendations for polyunsaturated fats, which are your essential fatty acids and cholesterol. Ideally, most of your fat intake is coming from healthy monounsaturated fats, followed by your essential fatty acids and then limiting the saturated fat. Cardiovascular disease is the general term for diseases of the heart and blood vessels. 83 million Americans suffer from some form of cardiovascular disease, with 1 million dying each year. In fact, heart disease is the leading cause of death for both men and women. One reason cardiovascular disease is so deadly is because the heart does not regenerate easily. If muscle is lost, say by a heart attack, the muscle doesn't regenerate. It forms scar tissue instead. Heart function then declines and failure can follow. Understanding the symptoms of a heart attack is important because early medical attention can save your life. Symptoms include pain or discomfort in the jaw, neck, or back, feeling weak, lightheaded or faint, chest pain or discomfort, pain or discomfort in the arms or shoulder, and shortness of breath. Women, however, may experience symptoms differently. Chest pain may not be present and they may feel unusually fatigued, dizzy, or weak. At the root of most forms of cardiovascular disease is atherosclerosis, which is hardening of the arteries. Everyone actually has signs of atherosclerosis, but how much at risk you are depends on how advanced it is. Can you slow it? Can you reverse it? So what causes plaque to form? Plaque starts off as fatty streaks of lipid materials along the inner walls of arteries, and this gradually enlarges and becomes hard. This damages the artery walls, stiffens them, and narrows them. Inflammation, as we have already discussed, is at the root of most chronic diseases. In atherosclerosis, inflammation plays a central role in all stages. Damage to artery walls can happen from a number of factors. including high LDL cholesterol, hypertension, diabetes, toxins from smoking, obesity, and infections. This damage leads to inflammation which then triggers the immune system to take action and try to repair the damages. Let's say we're talking about LDL cholesterol. LDL particles become trapped in the blood vessel walls and become oxidized by free radicals that are produced as a result of inflammation. Macrophages, a type of white blood cells, then rush to the scene to try to scavenge the oxidized LDL, but this ultimately worsens the situation as they become oxidized themselves once they're engorged and produce more inflammation while calling more immune responders to the scene. Muscle cells of the artery wall then try to help heal the damage by mixing with the engorged macrophages and now we have plaque formation. Once plaques have formed, they have the potential to rupture. An increase in blood pressure or spasm of the artery wall can tear apart the fibrous coat covering the plaque of the plaque, leading to rupture. When a rupture happens, the response is to clot the blood. While clot formation and subsequent dissolving happens normally, atherosclerosis disrupts this normal balance. Blood clots have the potential to cause harm. A blood clot called a thrombosis can remain stationary and attached to the blood vessel wall. It can then grow and shut off blood supply. Now it's called a thrombosis. Blood clots can also dislodge and travel and then block smaller arteries. This is called an embolism. The result can be tissue death, heart attack, and or stroke. Plaque formation also increases blood pressure. This is a result of hardening. and the blood vessels not being able to contract and expand properly. This leads to artery damage, which is favorable for more plaque formation and it strains the heart. As pressure builds, the arterial wall may become weak and balloon out. This forms an aneurysm, which can burst and lead to bleeding and death. Now we'll go through a series of slides and we'll take a look at risk factors for cardiovascular disease. Some are non-modifiable risk factors and some of them we have the potential to modify. So here's a look at our non-modifiable risk factors. We have age. An increase in age is associated with an increased risk for heart disease and so is gender. So for males, that age is over 45 and for females, that age is over 55. Genetics play a role. especially if you have an immediate family member that has had heart attack or some form of cardiovascular disease. So it's always good to ask your family members about their medical history if you can. Here's a look at modifiable risk factors. First, we have high LDL cholesterol, which we took a look at that a few slides ago and how that damages the artery wall. This increases risk. High HGL, which is our good cholesterol, decreases risk. Remember, HGL is more like a scavenger and helps carry cholesterol away from the body. Higlycerides, your blood fats, increase risk because they promote those fatty streaks and high VLDLs in the blood. Hypertension, as we also just saw a few slides ago, increases risk because we have these stiff arteries that create more stress and pressure. pressure and injury. Diabetes increases risk significantly. It kind of increases the progression of atherosclerosis, and there's also a lot of inflammation with diabetes. Regular activity decreases risk for several reasons. For one, you're strengthening the heart, your heart's muscle. You're stimulating new artery growth. promoting a healthy body weight, improving your blood lipid profile, insulin sensitivity, and reducing inflammation and managing blood pressure. Smoking increases risk. It's a direct toxin and it decreases oxygen delivery. Diet has a pretty heavy influence on the risk of cardiovascular disease. Saturated and trans fats can increase LDL cholesterol and LDL cholesterol that's high is associated with an increased risk of heart disease. Plant-based diets and Mediterranean type diets that have a foundation of plant-based foods like fruits, vegetables, whole grains, legumes, nuts, and seeds decrease risk. And then any diet that is full of antioxidants and fiber will also help be protective and control inflammation. And soluble fiber in particular helps remove cholesterol from the body. Obesity increases risk. There's inflammation there, but in particular, central obesity is a big risk factor because it's associated with visceral fat that collects in the midsection. around the organs where fat is not supposed to be stored and it's very metabolically active. Metabolic syndrome increases the risk of both cardiovascular disease and diabetes and metabolic syndrome is defined as having central obesity with at least two of the following other parameters. Low HDL, high triglyceride, high blood pressure and or fasting blood glucose. Here's a look at the potential for diet-related changes and how they impact LDL concentration in the blood by just reducing saturated fat, reducing weight even if it's just 10 pounds, increasing your soluble fiber intake. You can see the correlations here and what the possible LDL reduction might be. So even simple little changes have a fairly significant impact. And here are... the standards for blood lipids, body mass index, and blood pressure. So you might want to key in on the healthy section here at the bottom. Total blood cholesterol should be under 200, but really more importantly we want to look at LDL and HDL because that's included in total blood cholesterol and those lipoproteins in particular impact our health either positively or negatively. So LDL should be under 100. HDL should be over 60. Triglycerides should be under 150. And then you can see the recommendations for body mass index, which is an indirect measure for body fatness and then blood pressure. So now we're going to talk about essential fatty acids. As we've discussed, essential nutrients are those that must be supplied through the diet. There are two essential fatty acids, omega-6 and omega-3. They're both polyunsaturated fatty acids, and they're important for several reasons. They serve as raw material for eicosanoids, which we'll talk about in a minute. They are components of cell membranes, building blocks for hormones. They promote growth and vision. contribute lipids to the brain and nerves, help control immune function and blood clotting, and maintain healthy skin. Even though they're important and they're essential in the diet, deficiencies are actually pretty rare. We have more of a problem with imbalance, and we'll talk about that, but just so you know, deficiencies for these fatty acids are rare. But if there is a deficiency... This can lead to reduced growth and development in children, impaired immune function, and dry skin, just to name a few. Let's first talk about omega-6. Omega-6 is called linoleic acid, and it is the parent family. From linoleic acid, the body can synthesize arachidonic acid, which can be converted to eicosanoids. Eicosanoids are... hormone-like substances that help control functions in the body. The typical American diet supplies plenty of omega-6 fatty acids, primarily due to vegetable oil in processed, fried, and fast foods. You can see what the recommendations are here for men and women at the table at the bottom, and then you can see also the sources for omega-6. So nuts and seeds, have a different fatty acid profile, but some nuts and seeds in particular are, as we saw earlier in the lecture, are a more significant source of omega-6 fatty acids. Vegetable oils processed in fast foods because they contain vegetable oils. Dressings, spreads, fried foods, and then meat, dairy, and eggs also supply arachidonic acid. Omega-3 is called alpha-linolenic acid, and this is the parent family for omega-3. From alpha-linolenic acid, the body can synthesize two longer-chain fatty acids called EPA and DHA. You have probably heard of the importance of omega-3s, and we'll talk more about this. Omega-3s are undersupplied in the diet. acid is found in seeds like flax and chia, walnuts, soy, and microalgae. EPA and DHA can be supplied directly from fatty fish like salmon, for example, albacore tuna, lake trout. So cold water fatty fish tend to be good sources. And the fish aren't just naturally a good source. of EPA and DHA themselves, but they eat the microalgae in the sea and then do the conversion for you. So then they're now a directly a good source because they're able to store that in their fatty tissue. You might also see foods like eggs and some plant-based milks that are fortified with DHA or EPA. this fortification may be plant or animal source. A lot of times for eggs, they might put flax meal in the chicken feed, for example. Or perhaps they may add fish oil, but a lot of times they add flax seed. You can see the DRIs for omega-3 here. Note that the DRI is for the alpha-linolenic acid because that's the essential fatty acid. There's no actual DRI for DHA and EPA. But... some health professionals suggest that 250 to 500 milligrams per day is a good goal to shoot for and that can easily be achieved if you eat maybe not easily but it could be achieved if you have two servings of fatty fish per week or if you regularly include sources of alpha-linolenic acid Here's a closer look at the health benefits of EPA and DHA. EPA is converted to eicosanoids, just like that arachidonic acid is, and these eicosanoids help regulate cell activity, help reduce inflammation, and improve cardiovascular function. DHA is actually the predominant fatty acid in the brain and the retina of the eye, and DHA also helps reduce inflammation. and low levels of DHA in the blood have been associated with Alzheimer's and dementia. So it brings up another importance of chronic disease prevention with omega-3 fatty acids. We discussed how omega-6 is oversupplied and omega-3 is undersupplied in the diet. This imbalance has negative consequences for health. The body needs these essential fatty acids in proper balance for optimal health. Too much omega-6 can inhibit absorption of omega-3 because they compete for the same enzymes. The ideal ratio is 1 to 1 to 4 to 1, but most people are getting up to 25 to 1. Although omega-6 is essential, it is pretty easily met. And arachidonic acid has the potential to convert to metabolites that promote inflammation when we have this imbalance and this excess. It is thought that processed foods full of omega-6 from vegetable oils is a major contributor to throwing off the balance and promoting chronic inflammation. So why not just focus on meeting needs for alpha-linolenic acid? Why all the hype about EPA and DHA? Well, it is thought that the conversion of alpha-linolenic acid to EPA and DHA is not very efficient and that conversion is further limited by too much omega-6 in the diet. EPA and DHA can be supplied directly through fish. although most people don't eat the recommended amount or maybe they don't like fish or they're vegetarian or vegan some people use fish oil supplements but this should always be discussed with your doctor and if you are choosing a supplement a good quality supplement is ideal to avoid toxins and things like that and then fortified foods can also be an option but most people are not consuming enough directly and it is thought that these two fatty acids are deficient and leading to health problems. So this doesn't mean that those who don't eat fish should start because having alpha-linolenic acid as your main source of omega-3s might not be that detrimental and you still need those sources of alpha-linolenic linoleic acid because they're the essential fatty acid first most of the research has been done on the longer chain fatty acids which are the EPA and DHA so we really need more research on just including the alpha linoleic acid research on vegetarian diet shows that alpha linoleic acid imparts comparable cardiovascular benefits and that women vegetarians and vegans may be more efficient in converting that alpha-linolenic acid to EPA and DHA. And low blood levels of EPA and DHA may not be clinically significant because adults following a plant-based diet have a reduced risk of cardiovascular disease and children who follow vegetarian or vegan diets don't show impairments in growth and development. So now we're going to talk a little bit about hydrogenation and trans fats. Most of the fat in the U.S. diet comes from vegetable oil like we discussed. and this is supplied by fast and processed foods. The problem is many of these fats are not liquid oils. Rather, they are hydrogenated or partially hydrogenated. Hydrogenation is when you chemically alter fatty acids to make a once liquid oil into an oil that now behaves like a solid fat. Unsaturated fats or liquid oils are more susceptible to oxidation, which means they will go rancid. quicker, not to mention increase free radical activity. Hydrogenation makes foods much more shelf stable. So they do this by forcing hydrogen atoms into a liquid oil and that makes it saturated and that makes it solid at room temperature and more resistant to damage. And now it also has a high smoking point. So these are usually the reasons for the process of hydrogenation. But hydrogenation also destroys any nutrients, phytonutrients that were present in the unsaturated oil. Likely you've probably heard more about trans fatty acids. You see the value on the food label when you're looking at the nutrition facts panel. And you've heard about them for a good reason because they're harmful to health and as I think it's as a summer of 2018, they will actually be phased out of the U.S. food supply. During the process of hydrogenation, some of the unsaturated fatty acids change shape, and instead of becoming fully saturated with hydrogen, they take a different type of bond, which we'll see. It's called a trans bond, and we'll see that on the next slide. But that said, even though they still have this point of unsaturation, they still behave like a saturated fat and are shelf-stable with textural characteristics and a high smoke point. Trans fats, however, are bad for health, especially heart health, as they increase LDL cholesterol and inflammation while lowering HDL at the same time. Since trans fats were required on labels, many food manufacturers replaced them with saturated fats or fully hydrogenated oils. So it's important to always check labels and read ingredients. So here's a look at how hydrogenation yields both saturated and trans fats. You can see that we start off with an unsaturated fatty acid and if we force hydrogens that fatty acid now straightens out and it's fully saturated with hydrogen atoms and it's now saturated but sometimes during that process the fatty acid takes a trans shape and you can see how that bond is different so even though there's that point of unsaturation it still behaves like a saturated fat but is also very harmful for health at the same time Now just a few words on coconut oil because coconut oil in the past has been touted as a menace and more presently, you know, now and, you know, a couple years ago, coconut oil was touted as a miracle oil. In my opinion, I don't necessarily think it's a menace, but I certainly don't think that it's a miracle. But it helps to kind of know where this miracle belief is stemming from. And this miracle belief is centered around medium chain triglycerides. And medium chain triglycerides are unique because they're absorbed directly into the bloodstream and then they're rapidly used for energy versus being stored as fat. So a lot of times medium chain triglycerides are used for disorders where there's fat malabsorption. So they might be used in tube feeding or oral preparations. There have been some studies that link medium chain triglycerides to an increase in energy expenditure, but it's really not significant. And at the end of the day, it's not like you would want to add coconut oil to your diet as a weight loss strategy. There's also some studies that say they increase satiety, but really more research is needed with respect to coconut oil itself. There also seems to be... some disagreement over what chain length actually constitutes a medium chain triglyceride. So if you look at this fatty acid composition table here, focus in on lauric acid. The carbon chain length is 12. And so a lot of people who are touting that coconut oil is a really good source of these medium chain triglycerides kind of have it wrong because from a chemist's point of view, lauric acid is a long chain fatty acid. Okay. And that makes 90% of coconut a saturated fat. And so that will raise blood cholesterols or has the potential to raise LDL cholesterol. And that has been seen in research. So typically my advice with coconut oil is to use it within your saturated fat budget. Use it in place of other saturated fats like butter if you desire. But remember that it's still a dense source of calories. It might be worth it to maybe just ditch the oil and maybe eat a whole coconut product instead, like coconut flakes for example, because at least then you're getting fiber and vitamins and phytochemicals and other healthy benefits from the whole plant food itself versus just the oil. There is a video posted on Canvas under chapter five if you want to look at some of the research on coconut oil and its impact on blood cholesterol and also talks about its fatty acid composition as well. So the next few slides are just going to take you through some food-based strategies for choosing the right kind of fat and which fats we should limit. So the first thing to focus on is trying to find that ideal balance between omega-6 and omega-3. So for omega-6, we're easily getting enough. So a good strategy here is to focus on reducing omega-6 intake primarily through limiting processed and fast foods, but also starting to read ingredients. You'll notice how much vegetable oils are added to foods. Things like corn oil, safflower, sunflower, cottonseed oil. These are all really rich in omega-6 fatty acids. So one thing that you can do is choose in oil that is more of a monounsaturated fat like olive oil or avocado oil, for example. To increase omega-3 intake, try to include sources that are rich in alpha-linolenic acid daily. That could be just a tablespoon of ground flaxseed that you add to a smoothie or sprinkle in your oatmeal. If you eat fish, eating fatty fish two times per day, per week. You can try to include fortified foods. For meats, if you eat animal protein, choosing meats that are range or pasture raised because then they're grazing on grass and not on feed, which is usually high in omega-6. So the fatty acid profile of the animal is healthier. Supplements can be considered. There's also plant-based. supplements as well that are typically derived from microalgae. And just to kind of put it into perspective, the DRI is 12 to 17 grams a day for omega-6 fatty acids. A tablespoon of oil has about 14 grams of fat. So it's really, really easily met. And you can see how that can easily tip the balance because It's sneaking into our diet in so many different ways. Reducing saturated and trans fats is important. So choosing lean meats and or limiting portions, including more plant proteins like legumes, beans, peas, lentils, offer you more than just protein. They also offer fiber, vitamins, minerals, and they're really filling at the same time. Choosing lower fat dairy products, counting coconut oil as a saturated fat. watching the sauces, dressings, and spreads that you use, and then starting just to pay attention to nutrition information that's provided for chain restaurants or fast foods. Here's just a few facts down here. Two slices of pepperoni pizza is about nine grams saturated fat. So that's about half of, you know, the average person's saturated fat budget for the day. A Big Mac has eight grams of saturated fat and a... Grande Mocha Frappuccino has nine grams of saturated fat so easily can sneak in and add up. Then another strategy is to include monounsaturated fats in place of saturated fats. So if you can even focus on choosing whole foods over oil that's always more beneficial. So you can see the sources here olives, avocados, peanuts. And then what's really important too is if you're you know lowering saturated fat and you're looking for something to replace do not replace with refined carbohydrates and sugars that's just going to you know kind of moot the any kind of benefit that could be done just a little bit on the mediterranean diet because it has been connected to lowering the risk of cardiovascular disease And this connection to heart health really has to do with its anti-inflammatory properties. So traditionally, the Mediterranean diet was low in saturated fat, rich in unsaturated fat, mostly monounsaturated with a good source of omega-3s, and then rich in whole grains and fiber, and then rich in vitamins, minerals, and phytochemicals. So very heart protective. The Mediterranean diet today... might look a little different but traditionally this is the connection to heart health and the properties of the diet. So this here is from Dr. Weil and it's the Mediterranean diet pyramid and you can see that the foundation of the diet is really plant foods. Fish and seafood is included but other meats are limited as are sweets and so the foundation is mostly plant-based. This one here is a kind of a play on the Mediterranean diet pyramid and this is a plant-based version and it's conveniently called the vegetarian pyramid and this one is entirely plant-based but we're focusing on whole foods and with fats keeping the fat sources also coming from whole foods. So if you would like to practice, this table is here just to practice. So if you look at the 1800 calorie level for example, let's say you are following an 1800 calorie diet and your goal for fat was 30% of your total calories. Well, 30% of 1,800 is 540 calories. Now let's say we're using 10% as a limit for saturated fat. 10% of 1,800 calories is 180 calories. But it's probably more helpful to know, well, what does that mean in grams of fat? What should be my limit for grams of fat for the day? So remember, there's 9 calories per gram of fat. So for... 540 divided by 9 is 60 and then 180 divided by 9 is 20. So the limit for total fat would be 60 grams and the limit for saturated fat would be 20 grams. So this slide just shows you how simple substitutions can make a big impact on the quality of the fat or the type of fat. And then you can see the differences. The total fat, you know, pretty much stays the same, but you're really working on decreasing the saturated fat and increasing the unsaturated fat so the profile looks a little better. So controversy 5 is all about saturated fat and Is saturated fat really as harmful as we thought? And does that correlate with an increased risk of heart disease? So first go to Canvas and watch the two videos that are posted from nutritionfacts.org and listen to Dr. Greger speak about what prompted saturated fat to be back in the store. spotlight and then in the second video you'll take a closer look at the meta analyses and how the research was misused to promote saturated fat as being healthy again. So those are both posted in Canvas so please take a look. So one thing that we always have to think about when you see a headline is the red flag. Okay, if you see something that says the truth about or everything you knew about blank is wrong, then that's a red flag. With saturated fat especially, there's decades of research that show that the more saturated fat you eat, the higher your LDL cholesterol will raise. And so there is this clear link. between saturated fat and blood cholesterol. We can predict how much that LDL will rise based on saturated fat consumption, even if you have a stable calorie intake. So even though we know the connection between saturated fat and LDL, the debate really centered around if saturated fat actually causes heart disease. Okay, so we know that saturated fat can raise LDL. And LDL is associated with a higher risk of heart disease, but they kind of honed in on does saturated fat actually cause heart disease and then missed use the data from the meta-analysis. So please watch that video because he goes into pretty good detail about that. So there's some other limitations to research. on the connection between saturated fat and heart disease. It really depends on the type of study that is done. So here are just a few limitations and flaws. So first of all, there's been controlled and randomized trials that have been done to show the connection between saturated fat and LDL, which you can detect that. fairly quickly. So you can put somebody into a controlled environment and watch what happens. But these type of trials aren't very realistic to sustain for long periods of time to prove that saturated fat causes cardiovascular disease because you can't, heart disease takes a long time to progress and there's many other variables and you can't lock somebody in a room for years and years at a time and watch and see what happens. So instead, we have to rely on observational studies, which have limitations themselves and show an association, but not necessarily a causation. So like I mentioned that cardiovascular disease is complex and it takes time to advance. And then many other lifestyle factors impact its development and progression. So there's limitations in that itself. And then sometimes studies aren't even really stringent enough with reducing saturated fat to see a big enough impact. Many studies also don't account for what replaced the saturated fat. So for example, if you're replacing saturated fat with sugar and refined carbohydrates, well, that could very well cancel out the benefits of a saturated fat reduction. So ideally we want to be replacing with healthy items. Many studies also only analyze one nutrient. You know, for here, for example, that would be saturated fat instead of the entire diet. But we need to remember that we eat food. We don't go to the store and try to buy saturated fat. We eat food that is a mix of nutrients. So we also have to look at the whole diet itself. We'll wrap up with just a little bit on the cholesterol recommendations. Cholesterol. recommendations or rather limitations were always set at under 300 milligrams per day in the dietary guidelines. But in our most recent version of the dietary guidelines, the committee questioned the relationship between dietary cholesterol and blood cholesterol and whether cholesterol should be a nutrient of concern. So even though they went ahead and said, yes, you should limit dietary cholesterol as much as possible, they dropped that quantitative limit. Even despite there being decades of research that shows that dietary cholesterol does elevate blood cholesterol. And if you look closer at the report, what they actually called for was more research because the last meta-analysis that they did was fairly old. It was from 1998. And there's also a possible link to their being influenced from the egg industry and papers were in fact done and the research that was used to make these recommendations was research that was funded by the egg industry and this is a problem because eggs are one of the biggest sources of cholesterol for most americans because the egg yolk is a really rich source of cholesterol so You know, a little bit of fishy things going on there. But what it really does is just confuses the public. And, you know, people become confused and, you know, they might say, well, what the heck? I'm going to eat whatever I want because there's so much conflicting information and so much influence from food industry in to our research and guidelines. So it can give this green light to overindulge. It might even, you know, really be a moot point because foods with dietary cholesterol are typically also packaged with saturated fat. So it's not like we can really separate them out in most instances. So we should have a quantitative limit, you know, with anything because of this implication.

on one side, but they also have the potential to harm health on the other side. Ultimately, we must find a balance by moderating fat intake and, probably more importantly, the types of fat that we choose. Fat plays many roles in the body and also in food.

Fat provides fat-soluble vitamins, which are A, D, E, and K, essential fatty acids, which have to be obtained through the diet, Fat also helps carry fat-soluble vitamins through the lymphatic system for absorption. It's our chief form and long-term energy storage. It serves as an emergency fuel source, a material for cell membranes. It can be converted to other compounds when needed.

It is used for cushioning and protection of our organs. It offers insulation for extreme temperatures. and it fuels muscle work at low to moderate activity. Fat also plays a role in satiety or the feeling of fullness.

It helps slow the transit of food through the GI tract and also helps trigger a nerve signal to the brain to delay hunger. We have to be careful, though, because taste can easily override these signals, and it's very easy to overeat fatty foods. And last but not least, fat also helps contribute to the taste and smell of food.

which also kind of plays into why taste can easily override some of our satiety signals. There are three classes of lipids. Triglycerides, which represent about 95% of the lipids or fat found in food in the body.

Phospholipids, which are similar to triglycerides, but have a phosphorus-containing acid in place of one fatty acid. And sterols, of which cholesterol is the most common. Now we will start looking at each class of lipids, starting with triglycerides, the major form of fat found in the food and the body.

Fatty acids are rarely found free in the body. They are instead packaged as triglycerides. However, tissues in the body can easily disassemble and assemble triglycerides when needed. Your body is constantly disassembling and assembling them. Here you can see how a triglyceride is formed.

The name pretty much says it all. Three fatty acids are attached to a water soluble glycerol molecule backbone. Glycerol is a derivative of carbohydrate and composed of three carbons.

While the glycerol backbone remains the same, fatty acids can differ from one another. Chain length can vary as can saturation. Triglycerides typically contain various types of fatty acids.

Chain lengths can vary from anywhere from 4 to 24 carbons, with 18 being the most common. Fatty acids are chains of carbon atoms with hydrogen atoms attached. They have an acid group at one end, hence the name fatty acid, and a methyl group at the other end. The methyl group is alkaline derived from methane.

It contains one carbon atom bonded to three hydrogen atoms. Fatty acids differ in chain length or how many carbons they have. Long chain fatty acids are 12 to 24 carbons long and are commonly found in meat, fish, and nuts and seeds and their oils.

Medium chain triglycerides are six to ten carbons long. Coconut and palm oil contain some medium chain triglycerides, and medium chain triglycerides are also used clinically for fat malabsorption disorders. Lastly, short chain fatty acids have less than six carbons, and they are most commonly found in dairy products, but only in small amounts. Most of our Short chain fatty acids are actually produced by our friendly gut bacteria.

They ferment fibers to produce. short chain fatty acids, and these short chain fatty acids are then a fuel source for the cells of our colon and also helpful for human health. As mentioned, triglycerides are composed of different types of fatty acids. They can be a mixture of saturated and or unsaturated.

Saturated refers to how many hydrogen atoms the fatty acid chain can hold. A saturated fatty acid is filled to capacity with hydrogen atoms and has no double bonds. Unsaturated fatty acids include polyunsaturated and monounsaturated. Polyunsaturated fatty acids have two or more points of unsaturation, meaning they are missing two or more hydrogens and have two or more double bonds.

Monounsaturated fatty acids only have one point of unsaturation and consequently one double bond. Most of the triglycerides you eat in food have a mix of saturated and unsaturated fatty acids. Here are some examples of different fatty acids. Stearic acid is a saturated fatty acid. You can see that the carbons are completely saturated with hydrogen atoms.

Oleic acid is an example of a monounsaturated fatty acid found in olives and avocado. Linolenic acid and linoleic acid are both essential fatty acids that are polyunsaturated. The 3 in omega-3 represents where the first double bond is located from the methyl end.

Likewise for omega-6. The last figure shows that a triglyceride is most often a mixture of different types of fatty acid. This one in the right lower corner has one saturated, one monounsaturated, and one polyunsaturated.

How saturated a fatty acid is determines its melting point, which can also determine its healthfulness. Unsaturated fats are liquid at room temperature and are generally healthier. Conversely, saturated and trans fats are solid at room temperature and less healthy. If it is recommended to limit solid or saturated fats and use mono or polyunsaturated instead, you can gauge healthfulness by how hard something is at room temperature. Stability also differs.

Unsaturated fats are more vulnerable to oxidation and spoilage or rancidity. especially cold-pressed and unrefined oils. It is best to refrigerate these oils.

Some companies add antioxidant compounds to protect against spoilage. Keep in mind that when an oil or when heat is used to extract oil and oils are refined, vitamins, minerals, and phytochemicals are also lost. Here is a little game where you can guess the type of fat in different oils and foods. So olive oil is primarily monounsaturated. Soybean is polyunsaturated.

Ground beef is mostly saturated. Pecans, monounsaturated. Walnuts, polyunsaturated, a good source of omega-3s. Almonds, monounsaturated. Cheese.

saturated, coconut, saturated, avocados, monounsaturated, flax seeds, polyunsaturated, an excellent source of omega-3s, butter, saturated, and fish, polyunsaturated. Some fish like flax seeds and walnuts are also a really good source of omega-3s. This figure shows the fatty acid composition of common food fats. As we talked about earlier, most fats are a mixture of saturated, monounsaturated, and polyunsaturated fatty acids, which you can see here in this chart. The arrows to the right hand side represent whether those fats should be lower in the diet or higher in the diet when you're thinking about your total fat content.

So for example, we want to limit saturated fats and we want to limit vegetable oils that are high in omega-6s, but we need more omega-3s and having more monounsaturated fats that make up more of our total fat intake would be desirable. And this chart just gives you the fatty acid profile of different nuts and seeds. And you can see that they're also a mixture of saturated, although most are low in saturated fats, and then polyunsaturated and monounsaturated.

Now I want to discuss the other two classes of lipids, which are phospholipids and sterols. As mentioned, phospholipids are similar to triglycerides, but they only have two fatty acids. Their third molecule is a phosphorus molecule. This is unique because this phosphorus molecule makes them soluble in both water and fat.

At the same time, it has the ability to act as an emulsifier by keeping fats dispersed in water. Lecithin is a good example. This phospholipid emulsifies fats in foods. For example, oil and vinegar will separate with vinegar on the bottom and oil on the top. But what about mayonnaise?

It is primarily oil and vinegar, but with the help of lecithin found in egg yolks, which is an ingredient in mayonnaise, the fat is emulsified so that it is dispersed, stable, and spreadable. Lecithin is also produced by the body and present in all cell membranes. Phospholipids like to arrange themselves into two parallel layers with the hydrophilic glycerol phosphate group facing outwards and the hydrophobic or triglyceride part being forced inwards away from the water. This forms a protective layer in all cell membranes called the lipid bilayer. This bilayer is critical to cell functioning.

It lets certain molecules in and keep certain molecules out. out. So here is just a little more on lecithin.

Phospholipids are also found in the form of lecithin, which is found naturally in egg yolks, soybeans, sunflower seeds, and wheat germ. As mentioned in food, lecithin emulsifies fat and contributes to a stable and creamy product. You can see the chemical makeup of lecithin on the bottom. There's the two fatty acids and then the phosphate group, which makes it soluble in both water and fat. The last class of lipids is sterols.

Cholesterol is an example. And cholesterol has a complicated structure with rings of carbon with side chains of carbon, hydrogen, and oxygen. While we often associate cholesterol with heart disease, and rightly so because it forms plaque that clogs arteries, it also has important roles such as making emulsifiers in bile, forming the structure for cell membranes, and manufacturing vitamin D which is another sterol.

It also plays a role in the formation of hormones. That said, cholesterol is not essential. Our body can make what it needs. Cholesterol in the diet is only from animal products but sterols also exist in plants and confer health benefits. Even though they resemble cholesterol, they actually inhibit absorption, lowering blood levels.

You can find them in nuts, seeds, legumes, and fruits and vegetables in small amounts, and then some are also added to foods to impart that benefit. However, most of the research shows that you need to have at least two grams of these plant sterols to make significant difference in cholesterol levels and some of the foods that plant sterols are added to are maybe not the most health promoting foods that you would want to add to your diet like margarine for example or orange juice or granola bars but if you already eat these items in your diet and you switch to something that does have sterols then perhaps it might impart some kind of benefit As a reminder, an enzyme in saliva leads to a small amount of digestion. Infants actually have an enzyme secreted by the tongue to help digest milk fat, but this is pretty much inactive in adults.

There is little digestion of fat in the stomach as fat droplets separate from water and the stomach does not have enough churning power to disperse the fat. But as fat reaches the small intestine, it can now be Emulsified. This happens with the help of bile, which is secreted by the gallbladder, and it's alerted by a hormone to do so. And then it's secreted in the top portion of the small intestine, which is the duodenum. As you can see, bile, or as we've talked about, bile, actually you'll see that on the next slide, sorry.

Bile, also like an emulsifier in food, or phospholipid, attracts bile. both water and fat. Bile suspends fat droplets within watery fluids so that enzymes from the pancreas can then break them down into smaller components.

These enzymes split fatty acids from their glycerol backbone. The result is free fatty acids, phospholipids, and monoglycerides, which is still that glycerol backbone with just one fatty acid attached. They all cling together in a ball surrounded by the bile to remain emulsified. Now here you can see how bile emulsifies fat.

In the stomach, you can see that the fat is separated from the water so that the enzymes don't have access to the fat to be able to break them down and get them ready for absorption. But when fat enters the small intestine, just the right amount of bile is secreted, and that bile is water and fat soluble, so it more or less kind of pulls the droplets of fat down and suspends them in the watery fluid in the small intestine. And then after emulsification, more fat is exposed to the enzymes, and fat digestion proceeds along pretty efficiently.

Now that the fatty acids are split from glycerol and the fatty acids and monoglycerides are surrounded by bile, they are ready for absorption. But they have one more barrier to address. And this is the mucosal lining of the small intestine. The lining is watery and they need to get past this layer to enter the cells that line the small intestine. So bile comes to the rescue again.

It kind of acts like a shuttle and transports fat across the mucosal layer where the cells of the villi are. Fat is then extracted and bile is either absorbed and reused by the body or it is carried out with feces along with soluble fiber. Once cleaved by enzymes, glycerol and shorter chain fatty acids freely pass into the bloodstream and eventually make their way to the liver.

Larger fatty acids need more assistance, though. They still float in water, and they need a way to stay dispersed. The GI tract absorbs about 98% of triglycerides from a meal, making digestion and absorption very efficient. But the process takes time, and most fat is not excreted. That means we're really good at storing fatty acids if we don't need to use them for energy.

As mentioned, larger lipids need more assistance in order to be absorbed and packaged for transport. Larger lipids, like free fatty acids, combine with bile to form micelles. Now they are water-soluble enough to diffuse into intestinal cells.

Remember how triglycerides are always being assembled and disassembled in the body? Well, now triglycerides are reformed in the intestinal cells. where they then combine with proteins, cholesterol, and phospholipids to form a chylomicron.

A chylomicron is one type of lipoprotein. Lipoproteins are used to transport triglycerides. They allow fats to ride as passengers through the blood.

We will discuss other types of lipoproteins soon. Chylomicrons can now enter the lymphatic system through the lymph vessels in the villi where they will eventually be routed to the liver, then to the blood, and delivered to cells of the body. This slide gives you a nice summary of lipid digestion and absorption. And at the bottom right-hand corner, you'll also see that chylomicron that is there to help transport triglycerides from the digestive system.

So here is a summary of all of the types of lipoproteins in the body. So we just talked about the chylomicrons. They're made in the small intestine and they're a result from triglyceride digestion.

That TG means triglyceride. They are absorbed into the lymph after digestion. They're very rich in triglycerides and they're the largest and least dense.

So as the chylomicron travels through the bloodstream, cells in the body remove lipids as they pass through. And either they'll use them for energy or they will store them as fat. Now, liver cells then remove the chylomicron remnants from the blood and form new triglycerides in the liver. And this is where we get VLDL, which is very low density lipoprotein. These lipoproteins are secreted into the blood.

And they're still pretty rich in triglycerides and not very dense. And their job is to also transport triglycerides from the liver and deliver them to cells of the body. Now we have LDL, which is low density lipoprotein, which is made in the liver after VLDL loses most of its triglycerides.

So now the proportion of cholesterol is increasing. And this LDL is what we call. bad cholesterol.

It's also secreted into the blood and since it's lost most of its triglycerides, it's very rich in cholesterol and very large in light. Its job is to circulate and deliver triglyceride, cholesterol, and phospholipids to the cells of the body. But most of what it's doing is delivering cholesterol because it's very rich in cholesterol.

Lastly, we have HDL, which is high density lipoprotein. It's also made in the liver and maybe small amounts in the small intestine. And it's what we call good cholesterol.

It's secreted into the blood, and it's very rich in protein and small and dense. And its job is to kind of act like a scavenger. It picks up cholesterol from cells and then takes that cholesterol to the liver for recycling or disposal. So it helps lower cholesterol levels and manage them in a positive way. And here you can see each of the different lipoproteins and the density.

The density of a lipoprotein is determined by its lipid to protein ratio. All lipoproteins contain protein, cholesterol, phospholipids, and triglycerides in varying amounts. And LDL has a higher ratio of lipid to protein, about 80% lipid and 20% protein, and it's especially high in cholesterol.

And HDL, on the other hand, has more protein relative to its lipid content and about equal parts of lipid and protein. So this slide here gives you a nice summary of how lipoproteins are made and also lipid transport throughout the body. Lipoprotein concentrations in the blood have a connection to health.

High levels of LDL, which is our bad cholesterol, is associated with increased risk of heart disease, whereas higher HDL is associated with lower risk. Several lifestyle factors raise or lower LDL, and HDL. This includes weight management, dietary fat, soluble fiber, exercise, and alcohol consumption. As we've discussed, any type of food or macronutrient eaten in excess will be stored as fat. While this might be a detriment today, it was a survival mechanism for our ancestors who relied on fat stores during periods of famine.

When food was plentiful, fat was stored to prepare for limited food availability. Not all cells are designed to store fat, or at least not a lot. However, adipose tissue specializes in fat storage.

Think of fat cells like a balloon that can keep on expanding in size. The more fat they store, the larger they grow. In addition to fat storage, they also secrete hormones that regulate appetite.

The body reserves most fat stores and uses them when needed. The body's natural tendency is to conserve them though in case. They're needed in times of emergencies or increased or prolonged physical activity. Triglycerides, as we mentioned, are transported by chylomicrons to fat depots, such as under the skin, around the abdomen, breasts, hips, etc. They are stored for future energy needs, such as when fuel sources from food are low, then fat stores are called upon for energy and fuel.

As discussed, when there is plenty of fuel available, the body can convert excess carbohydrate to fat. But remember, this is not energy efficient as it requires several steps. The body also has enzymes to convert excess protein to fat or to glucose, but these are even less efficient. This doesn't mean that excess calories from protein and carbohydrates don't lead to fat storage. They do.

And mainly from sweets and meats, but fat storage from dietary fat is very efficient, requiring much fewer steps. Now, why isn't glucose the major form of stored energy? We know that it's critical to cells and very efficient as an energy source for cells, but it's also very bulky because glycogen holds water, about three grams per gram of carbohydrate. and the body just can't handle storing that much water.

Fat, on the other hand, is very compact, and it's packed tightly together without water. And remember, it provides nearly twice the amount of energy of carbohydrate or protein. When the body needs to use fat for energy, it dismantles triglycerides in the fat cells and releases fatty acid into the blood. Cells further break them down into fragments and combine with fragments from glucose, releasing more energy, carbon dioxide, and water.

Your fat stores are actually fueling about 80 to 90% of your body's needs when you're at rest or when food from fuel is low. And they're also a good fuel source during low to moderate activity. And the more trained a person becomes... the more able they are to spare their glycogen and rely on fat for energy. But you have to be at a low to moderate rate.

So think like an endurance event where you're going long periods of time. Now, to be able to lose fat, like say you're trying to lose weight and you want to lose body fat, you need to create a demand. So that might be restricting food intake or...

increasing energy or better yet both. And it's important to know that your fat cells do not shrink in numbers, but they shrink in size. Remember, they're like a balloon.

They can get bigger and bigger and bigger, but the number of fat cells that you have would be more, you know, dependent on genetics. Okay, on to recommendations for lipid intake or fat intake. We need some fat in the diet, otherwise we risk not getting enough essential fatty acids and fat-soluble vitamins. And, of course, not getting enough fat-soluble vitamins can lead to vitamin deficiencies.

Too little fat in the diet can also lead to hormonal problems along with decreased immunity and thyroid function. Dry, rough skin may also be present, perhaps, from inadequate vitamin A. DRIs recommend that 20 to 35% of total calories come from fat.

This is also true for athletes. Athletes rely on fat to fuel activity, their fat stores at least. Fat helps achieve their higher calorie needs.

So restricting fat isn't necessarily ideal for them for performance. Lower percentages of fat in the diet can be helpful for treating and reversing chronic disease, but this should really be evaluated on a case-by-case basis with a healthcare professional like a dietician or a doctor, for example. We will look at specifics for different fatty acids next, but in general, we want to lower saturated fat intake and focus on omega-3s and monounsaturated fats as our primary source of fats in the diet. Current fat intake in the US averages about 34% total calories from fat and 11 to 12% total calories from saturated fat.

This table here outlines lipid recommendations for healthy people. We already talked about total fat, which should be 20 to 35 percent of total calories. Saturated fat is generally 10 percent or less of total calories. However, the American Heart Association recommends to be even stricter with saturated fat if you have high blood cholesterol.

Trans fat should be as little as possible. And then you can see the recommendations for polyunsaturated fats, which are your essential fatty acids and cholesterol. Ideally, most of your fat intake is coming from healthy monounsaturated fats, followed by your essential fatty acids and then limiting the saturated fat. Cardiovascular disease is the general term for diseases of the heart and blood vessels. 83 million Americans suffer from some form of cardiovascular disease, with 1 million dying each year.

In fact, heart disease is the leading cause of death for both men and women. One reason cardiovascular disease is so deadly is because the heart does not regenerate easily. If muscle is lost, say by a heart attack, the muscle doesn't regenerate.

It forms scar tissue instead. Heart function then declines and failure can follow. Understanding the symptoms of a heart attack is important because early medical attention can save your life.

Symptoms include pain or discomfort in the jaw, neck, or back, feeling weak, lightheaded or faint, chest pain or discomfort, pain or discomfort in the arms or shoulder, and shortness of breath. Women, however, may experience symptoms differently. Chest pain may not be present and they may feel unusually fatigued, dizzy, or weak.

At the root of most forms of cardiovascular disease is atherosclerosis, which is hardening of the arteries. Everyone actually has signs of atherosclerosis, but how much at risk you are depends on how advanced it is. Can you slow it?

Can you reverse it? So what causes plaque to form? Plaque starts off as fatty streaks of lipid materials along the inner walls of arteries, and this gradually enlarges and becomes hard. This damages the artery walls, stiffens them, and narrows them.

Inflammation, as we have already discussed, is at the root of most chronic diseases. In atherosclerosis, inflammation plays a central role in all stages. Damage to artery walls can happen from a number of factors.

including high LDL cholesterol, hypertension, diabetes, toxins from smoking, obesity, and infections. This damage leads to inflammation which then triggers the immune system to take action and try to repair the damages. Let's say we're talking about LDL cholesterol. LDL particles become trapped in the blood vessel walls and become oxidized by free radicals that are produced as a result of inflammation.

Macrophages, a type of white blood cells, then rush to the scene to try to scavenge the oxidized LDL, but this ultimately worsens the situation as they become oxidized themselves once they're engorged and produce more inflammation while calling more immune responders to the scene. Muscle cells of the artery wall then try to help heal the damage by mixing with the engorged macrophages and now we have plaque formation. Once plaques have formed, they have the potential to rupture.

An increase in blood pressure or spasm of the artery wall can tear apart the fibrous coat covering the plaque of the plaque, leading to rupture. When a rupture happens, the response is to clot the blood. While clot formation and subsequent dissolving happens normally, atherosclerosis disrupts this normal balance. Blood clots have the potential to cause harm. A blood clot called a thrombosis can remain stationary and attached to the blood vessel wall.

It can then grow and shut off blood supply. Now it's called a thrombosis. Blood clots can also dislodge and travel and then block smaller arteries. This is called an embolism. The result can be tissue death, heart attack, and or stroke.

Plaque formation also increases blood pressure. This is a result of hardening. and the blood vessels not being able to contract and expand properly.

This leads to artery damage, which is favorable for more plaque formation and it strains the heart. As pressure builds, the arterial wall may become weak and balloon out. This forms an aneurysm, which can burst and lead to bleeding and death.

Now we'll go through a series of slides and we'll take a look at risk factors for cardiovascular disease. Some are non-modifiable risk factors and some of them we have the potential to modify. So here's a look at our non-modifiable risk factors.

We have age. An increase in age is associated with an increased risk for heart disease and so is gender. So for males, that age is over 45 and for females, that age is over 55. Genetics play a role. especially if you have an immediate family member that has had heart attack or some form of cardiovascular disease. So it's always good to ask your family members about their medical history if you can.

Here's a look at modifiable risk factors. First, we have high LDL cholesterol, which we took a look at that a few slides ago and how that damages the artery wall. This increases risk.

High HGL, which is our good cholesterol, decreases risk. Remember, HGL is more like a scavenger and helps carry cholesterol away from the body. Higlycerides, your blood fats, increase risk because they promote those fatty streaks and high VLDLs in the blood. Hypertension, as we also just saw a few slides ago, increases risk because we have these stiff arteries that create more stress and pressure.

pressure and injury. Diabetes increases risk significantly. It kind of increases the progression of atherosclerosis, and there's also a lot of inflammation with diabetes.

Regular activity decreases risk for several reasons. For one, you're strengthening the heart, your heart's muscle. You're stimulating new artery growth.

promoting a healthy body weight, improving your blood lipid profile, insulin sensitivity, and reducing inflammation and managing blood pressure. Smoking increases risk. It's a direct toxin and it decreases oxygen delivery. Diet has a pretty heavy influence on the risk of cardiovascular disease.

Saturated and trans fats can increase LDL cholesterol and LDL cholesterol that's high is associated with an increased risk of heart disease. Plant-based diets and Mediterranean type diets that have a foundation of plant-based foods like fruits, vegetables, whole grains, legumes, nuts, and seeds decrease risk. And then any diet that is full of antioxidants and fiber will also help be protective and control inflammation.

And soluble fiber in particular helps remove cholesterol from the body. Obesity increases risk. There's inflammation there, but in particular, central obesity is a big risk factor because it's associated with visceral fat that collects in the midsection. around the organs where fat is not supposed to be stored and it's very metabolically active. Metabolic syndrome increases the risk of both cardiovascular disease and diabetes and metabolic syndrome is defined as having central obesity with at least two of the following other parameters.

Low HDL, high triglyceride, high blood pressure and or fasting blood glucose. Here's a look at the potential for diet-related changes and how they impact LDL concentration in the blood by just reducing saturated fat, reducing weight even if it's just 10 pounds, increasing your soluble fiber intake. You can see the correlations here and what the possible LDL reduction might be. So even simple little changes have a fairly significant impact. And here are...

the standards for blood lipids, body mass index, and blood pressure. So you might want to key in on the healthy section here at the bottom. Total blood cholesterol should be under 200, but really more importantly we want to look at LDL and HDL because that's included in total blood cholesterol and those lipoproteins in particular impact our health either positively or negatively.

So LDL should be under 100. HDL should be over 60. Triglycerides should be under 150. And then you can see the recommendations for body mass index, which is an indirect measure for body fatness and then blood pressure. So now we're going to talk about essential fatty acids. As we've discussed, essential nutrients are those that must be supplied through the diet. There are two essential fatty acids, omega-6 and omega-3. They're both polyunsaturated fatty acids, and they're important for several reasons.

They serve as raw material for eicosanoids, which we'll talk about in a minute. They are components of cell membranes, building blocks for hormones. They promote growth and vision. contribute lipids to the brain and nerves, help control immune function and blood clotting, and maintain healthy skin. Even though they're important and they're essential in the diet, deficiencies are actually pretty rare.

We have more of a problem with imbalance, and we'll talk about that, but just so you know, deficiencies for these fatty acids are rare. But if there is a deficiency... This can lead to reduced growth and development in children, impaired immune function, and dry skin, just to name a few. Let's first talk about omega-6. Omega-6 is called linoleic acid, and it is the parent family.

From linoleic acid, the body can synthesize arachidonic acid, which can be converted to eicosanoids. Eicosanoids are... hormone-like substances that help control functions in the body. The typical American diet supplies plenty of omega-6 fatty acids, primarily due to vegetable oil in processed, fried, and fast foods.

You can see what the recommendations are here for men and women at the table at the bottom, and then you can see also the sources for omega-6. So nuts and seeds, have a different fatty acid profile, but some nuts and seeds in particular are, as we saw earlier in the lecture, are a more significant source of omega-6 fatty acids. Vegetable oils processed in fast foods because they contain vegetable oils.

Dressings, spreads, fried foods, and then meat, dairy, and eggs also supply arachidonic acid. Omega-3 is called alpha-linolenic acid, and this is the parent family for omega-3. From alpha-linolenic acid, the body can synthesize two longer-chain fatty acids called EPA and DHA. You have probably heard of the importance of omega-3s, and we'll talk more about this.

Omega-3s are undersupplied in the diet. acid is found in seeds like flax and chia, walnuts, soy, and microalgae. EPA and DHA can be supplied directly from fatty fish like salmon, for example, albacore tuna, lake trout.

So cold water fatty fish tend to be good sources. And the fish aren't just naturally a good source. of EPA and DHA themselves, but they eat the microalgae in the sea and then do the conversion for you. So then they're now a directly a good source because they're able to store that in their fatty tissue. You might also see foods like eggs and some plant-based milks that are fortified with DHA or EPA.

this fortification may be plant or animal source. A lot of times for eggs, they might put flax meal in the chicken feed, for example. Or perhaps they may add fish oil, but a lot of times they add flax seed. You can see the DRIs for omega-3 here.

Note that the DRI is for the alpha-linolenic acid because that's the essential fatty acid. There's no actual DRI for DHA and EPA. But...

some health professionals suggest that 250 to 500 milligrams per day is a good goal to shoot for and that can easily be achieved if you eat maybe not easily but it could be achieved if you have two servings of fatty fish per week or if you regularly include sources of alpha-linolenic acid Here's a closer look at the health benefits of EPA and DHA. EPA is converted to eicosanoids, just like that arachidonic acid is, and these eicosanoids help regulate cell activity, help reduce inflammation, and improve cardiovascular function. DHA is actually the predominant fatty acid in the brain and the retina of the eye, and DHA also helps reduce inflammation.

and low levels of DHA in the blood have been associated with Alzheimer's and dementia. So it brings up another importance of chronic disease prevention with omega-3 fatty acids. We discussed how omega-6 is oversupplied and omega-3 is undersupplied in the diet. This imbalance has negative consequences for health.

The body needs these essential fatty acids in proper balance for optimal health. Too much omega-6 can inhibit absorption of omega-3 because they compete for the same enzymes. The ideal ratio is 1 to 1 to 4 to 1, but most people are getting up to 25 to 1. Although omega-6 is essential, it is pretty easily met. And arachidonic acid has the potential to convert to metabolites that promote inflammation when we have this imbalance and this excess. It is thought that processed foods full of omega-6 from vegetable oils is a major contributor to throwing off the balance and promoting chronic inflammation.

So why not just focus on meeting needs for alpha-linolenic acid? Why all the hype about EPA and DHA? Well, it is thought that the conversion of alpha-linolenic acid to EPA and DHA is not very efficient and that conversion is further limited by too much omega-6 in the diet. EPA and DHA can be supplied directly through fish.

although most people don't eat the recommended amount or maybe they don't like fish or they're vegetarian or vegan some people use fish oil supplements but this should always be discussed with your doctor and if you are choosing a supplement a good quality supplement is ideal to avoid toxins and things like that and then fortified foods can also be an option but most people are not consuming enough directly and it is thought that these two fatty acids are deficient and leading to health problems. So this doesn't mean that those who don't eat fish should start because having alpha-linolenic acid as your main source of omega-3s might not be that detrimental and you still need those sources of alpha-linolenic linoleic acid because they're the essential fatty acid first most of the research has been done on the longer chain fatty acids which are the EPA and DHA so we really need more research on just including the alpha linoleic acid research on vegetarian diet shows that alpha linoleic acid imparts comparable cardiovascular benefits and that women vegetarians and vegans may be more efficient in converting that alpha-linolenic acid to EPA and DHA. And low blood levels of EPA and DHA may not be clinically significant because adults following a plant-based diet have a reduced risk of cardiovascular disease and children who follow vegetarian or vegan diets don't show impairments in growth and development.

So now we're going to talk a little bit about hydrogenation and trans fats. Most of the fat in the U.S. diet comes from vegetable oil like we discussed. and this is supplied by fast and processed foods. The problem is many of these fats are not liquid oils. Rather, they are hydrogenated or partially hydrogenated.

Hydrogenation is when you chemically alter fatty acids to make a once liquid oil into an oil that now behaves like a solid fat. Unsaturated fats or liquid oils are more susceptible to oxidation, which means they will go rancid. quicker, not to mention increase free radical activity. Hydrogenation makes foods much more shelf stable.

So they do this by forcing hydrogen atoms into a liquid oil and that makes it saturated and that makes it solid at room temperature and more resistant to damage. And now it also has a high smoking point. So these are usually the reasons for the process of hydrogenation.

But hydrogenation also destroys any nutrients, phytonutrients that were present in the unsaturated oil. Likely you've probably heard more about trans fatty acids. You see the value on the food label when you're looking at the nutrition facts panel. And you've heard about them for a good reason because they're harmful to health and as I think it's as a summer of 2018, they will actually be phased out of the U.S. food supply. During the process of hydrogenation, some of the unsaturated fatty acids change shape, and instead of becoming fully saturated with hydrogen, they take a different type of bond, which we'll see.

It's called a trans bond, and we'll see that on the next slide. But that said, even though they still have this point of unsaturation, they still behave like a saturated fat and are shelf-stable with textural characteristics and a high smoke point. Trans fats, however, are bad for health, especially heart health, as they increase LDL cholesterol and inflammation while lowering HDL at the same time. Since trans fats were required on labels, many food manufacturers replaced them with saturated fats or fully hydrogenated oils. So it's important to always check labels and read ingredients.

So here's a look at how hydrogenation yields both saturated and trans fats. You can see that we start off with an unsaturated fatty acid and if we force hydrogens that fatty acid now straightens out and it's fully saturated with hydrogen atoms and it's now saturated but sometimes during that process the fatty acid takes a trans shape and you can see how that bond is different so even though there's that point of unsaturation it still behaves like a saturated fat but is also very harmful for health at the same time Now just a few words on coconut oil because coconut oil in the past has been touted as a menace and more presently, you know, now and, you know, a couple years ago, coconut oil was touted as a miracle oil. In my opinion, I don't necessarily think it's a menace, but I certainly don't think that it's a miracle.

But it helps to kind of know where this miracle belief is stemming from. And this miracle belief is centered around medium chain triglycerides. And medium chain triglycerides are unique because they're absorbed directly into the bloodstream and then they're rapidly used for energy versus being stored as fat. So a lot of times medium chain triglycerides are used for disorders where there's fat malabsorption. So they might be used in tube feeding or oral preparations.

There have been some studies that link medium chain triglycerides to an increase in energy expenditure, but it's really not significant. And at the end of the day, it's not like you would want to add coconut oil to your diet as a weight loss strategy. There's also some studies that say they increase satiety, but really more research is needed with respect to coconut oil itself. There also seems to be... some disagreement over what chain length actually constitutes a medium chain triglyceride.

So if you look at this fatty acid composition table here, focus in on lauric acid. The carbon chain length is 12. And so a lot of people who are touting that coconut oil is a really good source of these medium chain triglycerides kind of have it wrong because from a chemist's point of view, lauric acid is a long chain fatty acid. Okay. And that makes 90% of coconut a saturated fat. And so that will raise blood cholesterols or has the potential to raise LDL cholesterol.

And that has been seen in research. So typically my advice with coconut oil is to use it within your saturated fat budget. Use it in place of other saturated fats like butter if you desire. But remember that it's still a dense source of calories. It might be worth it to maybe just ditch the oil and maybe eat a whole coconut product instead, like coconut flakes for example, because at least then you're getting fiber and vitamins and phytochemicals and other healthy benefits from the whole plant food itself versus just the oil.

There is a video posted on Canvas under chapter five if you want to look at some of the research on coconut oil and its impact on blood cholesterol and also talks about its fatty acid composition as well. So the next few slides are just going to take you through some food-based strategies for choosing the right kind of fat and which fats we should limit. So the first thing to focus on is trying to find that ideal balance between omega-6 and omega-3.

So for omega-6, we're easily getting enough. So a good strategy here is to focus on reducing omega-6 intake primarily through limiting processed and fast foods, but also starting to read ingredients. You'll notice how much vegetable oils are added to foods.

Things like corn oil, safflower, sunflower, cottonseed oil. These are all really rich in omega-6 fatty acids. So one thing that you can do is choose in oil that is more of a monounsaturated fat like olive oil or avocado oil, for example. To increase omega-3 intake, try to include sources that are rich in alpha-linolenic acid daily.

That could be just a tablespoon of ground flaxseed that you add to a smoothie or sprinkle in your oatmeal. If you eat fish, eating fatty fish two times per day, per week. You can try to include fortified foods. For meats, if you eat animal protein, choosing meats that are range or pasture raised because then they're grazing on grass and not on feed, which is usually high in omega-6.

So the fatty acid profile of the animal is healthier. Supplements can be considered. There's also plant-based.

supplements as well that are typically derived from microalgae. And just to kind of put it into perspective, the DRI is 12 to 17 grams a day for omega-6 fatty acids. A tablespoon of oil has about 14 grams of fat.

So it's really, really easily met. And you can see how that can easily tip the balance because It's sneaking into our diet in so many different ways. Reducing saturated and trans fats is important.

So choosing lean meats and or limiting portions, including more plant proteins like legumes, beans, peas, lentils, offer you more than just protein. They also offer fiber, vitamins, minerals, and they're really filling at the same time. Choosing lower fat dairy products, counting coconut oil as a saturated fat. watching the sauces, dressings, and spreads that you use, and then starting just to pay attention to nutrition information that's provided for chain restaurants or fast foods.

Here's just a few facts down here. Two slices of pepperoni pizza is about nine grams saturated fat. So that's about half of, you know, the average person's saturated fat budget for the day.

A Big Mac has eight grams of saturated fat and a... Grande Mocha Frappuccino has nine grams of saturated fat so easily can sneak in and add up. Then another strategy is to include monounsaturated fats in place of saturated fats. So if you can even focus on choosing whole foods over oil that's always more beneficial. So you can see the sources here olives, avocados, peanuts.

And then what's really important too is if you're you know lowering saturated fat and you're looking for something to replace do not replace with refined carbohydrates and sugars that's just going to you know kind of moot the any kind of benefit that could be done just a little bit on the mediterranean diet because it has been connected to lowering the risk of cardiovascular disease And this connection to heart health really has to do with its anti-inflammatory properties. So traditionally, the Mediterranean diet was low in saturated fat, rich in unsaturated fat, mostly monounsaturated with a good source of omega-3s, and then rich in whole grains and fiber, and then rich in vitamins, minerals, and phytochemicals. So very heart protective. The Mediterranean diet today... might look a little different but traditionally this is the connection to heart health and the properties of the diet.

So this here is from Dr. Weil and it's the Mediterranean diet pyramid and you can see that the foundation of the diet is really plant foods. Fish and seafood is included but other meats are limited as are sweets and so the foundation is mostly plant-based. This one here is a kind of a play on the Mediterranean diet pyramid and this is a plant-based version and it's conveniently called the vegetarian pyramid and this one is entirely plant-based but we're focusing on whole foods and with fats keeping the fat sources also coming from whole foods. So if you would like to practice, this table is here just to practice.

So if you look at the 1800 calorie level for example, let's say you are following an 1800 calorie diet and your goal for fat was 30% of your total calories. Well, 30% of 1,800 is 540 calories. Now let's say we're using 10% as a limit for saturated fat.

10% of 1,800 calories is 180 calories. But it's probably more helpful to know, well, what does that mean in grams of fat? What should be my limit for grams of fat for the day? So remember, there's 9 calories per gram of fat. So for...

540 divided by 9 is 60 and then 180 divided by 9 is 20. So the limit for total fat would be 60 grams and the limit for saturated fat would be 20 grams. So this slide just shows you how simple substitutions can make a big impact on the quality of the fat or the type of fat. And then you can see the differences.

The total fat, you know, pretty much stays the same, but you're really working on decreasing the saturated fat and increasing the unsaturated fat so the profile looks a little better. So controversy 5 is all about saturated fat and Is saturated fat really as harmful as we thought? And does that correlate with an increased risk of heart disease? So first go to Canvas and watch the two videos that are posted from nutritionfacts.org and listen to Dr. Greger speak about what prompted saturated fat to be back in the store.

spotlight and then in the second video you'll take a closer look at the meta analyses and how the research was misused to promote saturated fat as being healthy again. So those are both posted in Canvas so please take a look. So one thing that we always have to think about when you see a headline is the red flag. Okay, if you see something that says the truth about or everything you knew about blank is wrong, then that's a red flag.

With saturated fat especially, there's decades of research that show that the more saturated fat you eat, the higher your LDL cholesterol will raise. And so there is this clear link. between saturated fat and blood cholesterol. We can predict how much that LDL will rise based on saturated fat consumption, even if you have a stable calorie intake.

So even though we know the connection between saturated fat and LDL, the debate really centered around if saturated fat actually causes heart disease. Okay, so we know that saturated fat can raise LDL. And LDL is associated with a higher risk of heart disease, but they kind of honed in on does saturated fat actually cause heart disease and then missed use the data from the meta-analysis. So please watch that video because he goes into pretty good detail about that. So there's some other limitations to research.

on the connection between saturated fat and heart disease. It really depends on the type of study that is done. So here are just a few limitations and flaws. So first of all, there's been controlled and randomized trials that have been done to show the connection between saturated fat and LDL, which you can detect that.

fairly quickly. So you can put somebody into a controlled environment and watch what happens. But these type of trials aren't very realistic to sustain for long periods of time to prove that saturated fat causes cardiovascular disease because you can't, heart disease takes a long time to progress and there's many other variables and you can't lock somebody in a room for years and years at a time and watch and see what happens.

So instead, we have to rely on observational studies, which have limitations themselves and show an association, but not necessarily a causation. So like I mentioned that cardiovascular disease is complex and it takes time to advance. And then many other lifestyle factors impact its development and progression.

So there's limitations in that itself. And then sometimes studies aren't even really stringent enough with reducing saturated fat to see a big enough impact. Many studies also don't account for what replaced the saturated fat. So for example, if you're replacing saturated fat with sugar and refined carbohydrates, well, that could very well cancel out the benefits of a saturated fat reduction.

So ideally we want to be replacing with healthy items. Many studies also only analyze one nutrient. You know, for here, for example, that would be saturated fat instead of the entire diet. But we need to remember that we eat food.

We don't go to the store and try to buy saturated fat. We eat food that is a mix of nutrients. So we also have to look at the whole diet itself. We'll wrap up with just a little bit on the cholesterol recommendations.

Cholesterol. recommendations or rather limitations were always set at under 300 milligrams per day in the dietary guidelines. But in our most recent version of the dietary guidelines, the committee questioned the relationship between dietary cholesterol and blood cholesterol and whether cholesterol should be a nutrient of concern. So even though they went ahead and said, yes, you should limit dietary cholesterol as much as possible, they dropped that quantitative limit.

Even despite there being decades of research that shows that dietary cholesterol does elevate blood cholesterol. And if you look closer at the report, what they actually called for was more research because the last meta-analysis that they did was fairly old. It was from 1998. And there's also a possible link to their being influenced from the egg industry and papers were in fact done and the research that was used to make these recommendations was research that was funded by the egg industry and this is a problem because eggs are one of the biggest sources of cholesterol for most americans because the egg yolk is a really rich source of cholesterol so You know, a little bit of fishy things going on there.

But what it really does is just confuses the public. And, you know, people become confused and, you know, they might say, well, what the heck? I'm going to eat whatever I want because there's so much conflicting information and so much influence from food industry in to our research and guidelines.

So it can give this green light to overindulge. It might even, you know, really be a moot point because foods with dietary cholesterol are typically also packaged with saturated fat. So it's not like we can really separate them out in most instances. So we should have a quantitative limit, you know, with anything because of this implication.

Transcript for:Understanding Lipids and Healthy Fats

Transcript for:
Understanding Lipids and Healthy Fats