i'm professor giusti and this is nutrition 300 chapter 8 water and minerals this is part 2 of the audio lectures for chapter 8 on water and minerals so let's take a look at water water is of course one of the six classes of essential nutrients it's pretty well known that water is important for normal function inside the body and it's even important for our our very survival you probably have heard before and it's true that without any sources of water the human body can only live for maybe five to seven days depending on environmental conditions so of course water is critical for life and also important for normal function inside the human body but what does water actually do so even though we talk about how important water is to normal function in the body and health and its essential nutrient much of the time we don't actually talk about what water does so internally water serves a number of purposes for the human body one is that it's actually a structural element of our body and oftentimes we don't think about water as a structural element the way we would think of calcium and phosphorus as part of our bones or protein part of our muscles and skin and connective tissue but inside of our cells most cells by weight and by volume are predominantly water it gives water its structure its shape excuse me gives cells structure its shape and its volume now of course some of that volume is taken up by other things some of that shape of course is made up of the phospholipid bilayer that's part of the cell membranes which we talked about in chapter five but inside of the cell it's mostly water so it's a major structural element of most of the cells inside the human body also water is really important for chemical reactions it's the main solvent in which almost all chemical reactions take place inside the body and of course we have countless chemical reactions that are happening on an ongoing basis to sustain life also in some cases water is a participant in those chemical reactions sometimes as one of the reactants and many times as a byproduct of chemical reactions as well water has a number of other important roles too it's really important as part of our bloodstream it gives our blood its volume so the important volume part of the liquid for our blood and also water is important broadly speaking for our transport and also removal of waste products from the body and of course as we'll see a little bit later it's really important for helping to maintain our internal temperature by helping the body to get rid of extra internal energy internal heat energy and we get rid of that in the main way by sweating of course we need water for that let's take a closer look at where water is inside the body so if you look at our total body water most of our body weight actually is water so depending on some variances in body fat from one person to another for each person about 60 percent of their total body weight is water where is all this water well most of it is inside of our cells what we call intracellular water intracellular cellular means within the cells so most of that water is inside of cells about two-thirds is inside of cells and about one-third is outside of cells what we call extracellular so where's the water that's extracellular well that's the water for example that's in between cells or the water that's in our bloodstream or in our lymphatic system and a few other places that are outside of cells as well taking a closer look at this as i mentioned earlier about two-thirds two-thirds of our body water is inside of cells and about one-third outside now why is it that two-thirds inside and one-third outside well this is actually the appropriate ratio that keeps our body functioning properly it also has to do with the number of cells that we have and most of those cells remember are primarily water on the inside this is why we have the predominance of our body water that's inside of cells however it is important to note that when we lose water from the body most mostly we're losing that water from our extracellular fluid or extracellular water as an example when we sweat water goes to the skin surface and then is that evaporates well where does that water come from before it gets to the skin surface mostly it was water that was inside of our bloodstream this is why when we sweat a lot and we become dehydrated our blood volume actually decreases this is one of the reasons that our our heart rate or our pulse goes up when we are dehydrated because that water has come out of our our bloodstream or the water that was in our bloodstream our body works really hard though to keep water in the right places in the right ratios it uses electrolytes for this and it uses a few other large protein compounds to do this as well so not only do we need our body to keep the water in the right places again mostly inside of cells about two-thirds inside cells and one-third outside but also we have to have the appropriate amount of total water inside the body too what we mean by this is our intake of water has to kind of match up with our losses of water or even exceed our losses of water we lose water every day from the body it's a normal part of metabolism for us to lose water every day and we'll see in a few minutes how and where we actually lose water but again it's a normal metabolic processes where we lose water from the body every day so in order to maintain our hydration status we need to take in water from sources outside the body this is why it is indeed an essential nutrient because we have to get it from an outside source if our water intake is less than our water losses this is what results in what's commonly called dehydration if our intake and losses are about equal this is in this is typically referred to as being in water balance or proper hydration and if we take in more water than we need or more water than we're losing this results in what we call hyper hydration now hyper hydration is not a commonly used term also hyper hydration is typically a short lived state inside the body and the reason for this is when we have extra water intake meaning our intake is greater than our losses our body typically just gets rid of that extra water via urination so we just pee out that extra water so while we might be hyper hydrated for a short amount of time our body deals with that extra water intake by sending it out in the urine so water intake we're talking about water that's coming in from outside sources coming from food and beverages that we consume one of the sources of water however isn't really an external source it's an internal source called metabolic water so some water inside our body is actually produced internally as a byproduct of normal chemical reactions although as you can see here based on the actual amounts in terms of liters or milliliters that are produced from metabolic rat water it's really a small fraction of the bar of the amount of water that we need in total to maintain hydration and on the losses side you can see that the majority of our water losses come from urination again this is a normal metabolic process the main way that we get rid of byproducts and potential toxins out of the body is via urination also depending on environmental conditions we may lose one to two liters of water per day via sweat and if we're exercising likely we would lose even more from sweating we also lose a little bit from fecal matter and also what's referred to as breath water losses just in breathing actually there's some water vapor that comes out as well too though losses from fecal matter and from breath water relatively speaking are much smaller than the amount of losses in urine and sweat so ultimately when we're looking at water balance or hydration status we're comparing losses and intake now it is possible to take in too much water and have water toxicity this is extremely uncommon though how does this happen well this only happens with extreme intake in a very short amount of time for example if you were drinking gallons of water in a very short amount of time it could be potentially toxic and actually deadly if you take in way too much as a bit of a side note sadly this does happen on a somewhat frequent basis sometimes by accident for example here in the sacramento area there was a woman who died from water toxicity after drinking gallons of water for a local radio station contest she drank gallons of water in a very short amount of time and diet tragically so water toxicity is uncommon but it's definitely also one of those things that nutritionists will tell you don't try this at home there's no reason to drink gallons of water in a short amount of time it is dangerous don't do it now if you sip on water throughout the day that's very different that's typically safe to do what's more common is dehydration mild dehydration this is very common when just haven't taken enough water during the day and because our body is constantly losing and using water mild dehydration is pretty common but it's also very easy to correct simply just by drinking water or by other beverages that have high water content extreme dehydration can be dangerous this can also be deadly too again it's only deadly in the most extreme situations we'll cover cover those here in just a couple minutes in terms of water intake to keep us hydrated large-scale studies for years have shown that most of water intake for americans actually comes from fluids but it depends on your intake of beverages and your intake of foods and what types of foods we'll get to the foods here in just a minute so when we say fluids we're talking about well we can start with simple water intake it could be tap water could be bottled water it could be filtered water lots of ways to take in in water and you might find this interesting that over the last several decades research shows that people are actually cons americans are actually consuming more just plain water on a regular basis but certainly we get a lot of fluid intake and water intake from other beverages that we consume including like soft drinks sports drinks even milk and juices and plenty of other caffeinated beverages and now there are so many different beverages that are being produced even zero calorie calorie beverages like flavored carbonated waters and those contribute to our hydration status as well believe it or not foods can actually contribute a lot of water to our intake as well but it depends on what foods we're taking in so for example fruits and vegetables by weight and by volume are mostly water most whole fruits and vegetables are somewhere between 60 and 90 percent water by weight so if you consume a lot of fruits and vegetables this contributes significantly to your water intake it actually means that you need to take in less water to maintain your hydration status again metabolic water that's produced internally only contributes a very small amount to our overall water in this case it's not intake but our overall production of water that can contribute to our hydration status and if you take a look at some of the foods on this chart you can see what we're talking about on the very bottom of this chart you can see the percent of excuse me percent water by weight of these commonly consumed foods and you can see that many of these fruits and vegetables are 70 80 even 90 percent water by weight so that means if you're consuming a lot of high water content fruits and vegetables and even some other foods as you can see here as well too like whole meat products like chicken and steak those actually do contribute to your water intake however most people won't be able to fully hydrate themselves just by consuming foods even if there you have a high consumption of fruits and vegetables typically in order to maintain proper hydration status individuals need to take in fluids and most likely water on a regular basis to stay well hydrated looking at losses once again the majority of our water losses come from normal metabolic processes including urination where again we are urination as we touched on way back in chapter three our kidneys filter our blood they filter out byproducts and potential toxins and our body excretes them in the urine this is a normal process but of course it causes us to use water in this process and lose it from the body perspiration and sweating this is something that we do pretty much every day you may not think that even in the winter you sweat a lot but there's always some amount of perspiration that's being sent out to the skin surface certainly there's a lot more when the weather is hot so environmental conditions will affect perspiration sweating as will activity level will certainly affect perspiration sweating too and as i mentioned earlier breath water and the small amount of water that you lose in the fecal matter also contribute to water losses overall we typically lose between two and three liters of water every day but it can be significantly higher with activity and hotter environmental conditions now there are some dietary factors that contribute to water balance as well the two main dietary factors that have a negative effect on our water balance are the consumption of diuretics and the consumption of salt or sodium so what are diuretics in very basic terms diuretics are substances that we take in that cause us to lose additional water from the body the two most common diuretics that americans take in are alcohol and caffeine these two diuretics cause us to lose extra water water that's excreted with the urine so anytime that a person is consuming alcohol or caffeine they should consume extra water to help try to maintain their hydration status and then the consumption of salt and sodium can also affect water balance in the body as well and while salt or sodium does not actually cause us to lose water from the body what extra sodium intake causes and for us to retain water or trap water in the wrong places inside the body so when we have extra salt or sodium this causes water retention but it causes water retention in tissue spaces and this actually causes an imbalance of water inside the body in order to get rid of this extra sodium and this extra water that we're retaining it requires that we consume extra water from the diet and in very basic terms once again i know i like to use the basic terms what that helps the body to do is to wash out the extra salt and wash out the extra water that was being trapped or retained in the body to wash out that extra sodium and water into the urine and get our hydration status back into balance so again if you're consuming diuretics or high amounts of sodium in the diet extra water is required to maintain hydration status and water and electrolyte balance inside the body so let's talk about how the body responds to challenges in water balance because the body doesn't really like to be dehydrated nor does it like to have electrode imbalances we have systems inside the body that are designed to retain water and electrolytes when needed in order to maintain water and electrolyte balance the three main hormonal responses you can see here one is adh anti-diuretic homan hormone we also have the renin system which includes angiotensin one and two and we also have the aldosterone hormone as well these hormones are chemical messengers that the body sends out in response to dehydration or electrode imbalances to help try to maintain our water and electrolyte balance so let's take a closer look and see how this works whenever we don't have enough water coming in our body can sense that and in sensing it it does a couple things one is that it triggers up in our brain a part of the brain that senses dehydration and it causes thirst also when we have decreased water intake our body decreases our saliva secretion in the mouth causes kind of a drying of the mouth these two things lead us to try to go and find water drink water and that helps to maintain our hydration in addition whenever we have dehydration the body senses that as well too mostly by decreases in blood volume as i talked about earlier because we lose water from the bloodstream when we become dehydrated this causes the release of adh or anti-diuretic hormone this sends a message to the kidneys to tell our kidneys to conserve water essentially to reabsorb more water don't send as much out into the urine this is why women become dehydrated we urinate less frequency or frequently or the urine volume goes down because anti-diuretic hormone helps to retain water inside the body in addition to this when we become dehydrated the body tries to maintain our blood pressure as well as our electrolyte balance so another signal is sent out that tells our body to start retaining sodium inside the body and also to increase our our blood pressure by constricting blood vessels these two things help to maintain our electrolyte balance and also maintain our blood pressure because as we become dehydrated our blood pressure naturally goes down which might sound like a good thing because a lot of people know that high blood pressure is bad but actually very low blood blood pressure is bad as well so these responses help to maintain our electrolyte balance and our blood pressure so in total the electrolyte excuse me the hormonal responses to dehydration help us to maintain normal function by retaining water sodium and maintaining our blood pressure but if the dehydration goes on and on you can see some of the symptoms go from mildly annoying to noticeable to deadly and because of the effects of dehydration on our bloodstream which affects our cardiovascular system because of the effects of dehydration on our electrolytes it affects our central nervous nervous system including our brain stimulation of muscles as well as all of our nervous system as well and also starts to affect our kidneys and our ability to regulate our body temperature so you can see that on this chart as these numbers on the left hand side increase as you go down this is percent of body water loss from dehydration and you can see that the symptoms get really bad at first a person may just feel like they're becoming overheated may see flushing of the skin may feel kind of tired and as time goes on you start to see more of the effects on the cardiovascular system on the central nervous system actually on the respiratory system as well too because what happens as the blood volume becomes decreased the co2 levels go up in the blood and this causes respiratory problems as well as things get worse and worse then you have organ systems like our kidneys that start to shut down muscles become there's mental confusion and then there can also be a complete loss of control of the muscles in extreme cases because of the effects on the central nervous system you usually see loss of consciousness and because of the extreme dehydration the kidney shut down completely now the blood is not being filtered so that means again metabolic byproducts and toxins are building up in the blood and this can cause enzyme dysfunction and ultimately in extreme cases death of course this isn't only in the most extreme cases where a person continues to lose water from dehydration these would be extreme cases where somebody for example is is competing in athletics that would be hours and hours and hours of high intensity activity in the heat something like a triathlon or extreme running competitions or this would be also the case if somebody was for example lost out in as you might say in the desert or in a really hot condition and was not able to get out of the elements didn't have access to water and continue to become dehydrated over the course of a few days obviously we want to avoid this as much as possible this typically only happens in the most extreme cases of of dehydration so what do nutrition experts recommend in order to maintain hydration well the current ai or adequate intake for adults as you can see from from this slide it's about two to three liters per day for adults however these recommendations are very general and the reason for this is that there are a number of factors that affect how much water a person needs to maintain their hydration status these factors include metabolic rate body size activity level environmental conditions so this adequate intake of a few liters of water per day is really more of a general recommendation again the variations from person to person are significant in the need for water so what's the best recommendation that nutritionists can make well total intake again typically needs to be two to three maybe four liters of water per day but the recommendation is to monitor frequency and clarity of the urine if you have nearly clear urine on a fairly regular basis this probably means that you're well hydrated and what's the reason for that well if you're well hydrated it means that there's extra water that's being expelled by the kidney and this indicates that you're relatively well hydrated because extra water is being sent out if urination is less frequent and the color of the urine becomes darker what that indicates is that you're probably more dehydrated because more water is being retained inside the body and this causes less frequent urination and darker color urine so in order to really evaluate on an individual basis whether you're staying hydrated or well hydrated check the frequency and clarity of the urine and this concludes part two of the audio slides for chapter eight in nutrition 300.