Dietary Fats and Heart Health

Overview

This lecture continues the discussion on dietary fats, detailing the types of fatty acids, the effects of hydrogenation, essential fatty acids, dietary recommendations, sources of saturated fat, the Mediterranean diet, and the role of lipoproteins in heart health.

Saturated vs. Unsaturated Fatty Acids

• Saturated fatty acids have no double bonds between central carbons and are fully "saturated" with hydrogen.
• Unsaturated fatty acids have at least one double bond, making them less saturated with hydrogen.
• Cis fatty acids (naturally occurring unsaturated fats) have hydrogens on the same side of the double bond.
• Trans fatty acids (mainly man-made) have hydrogens on opposite sides of the double bond, often created during hydrogenation.

Hydrogenation and Trans Fats

• Hydrogenation adds hydrogen to oils, making them solid and more shelf-stable (e.g., shortening).
• Partial hydrogenation creates trans fats, which increase cardiovascular disease risk.
• The FDA banned partially hydrogenated oils (trans fats) in most foods as of 2021.
• Trans fats raise LDL ("bad cholesterol") and decrease vitamin K activity.
• Naturally occurring trans fats in dairy and beef are not shown to be harmful.

Essential Fatty Acids: Omega-3 and Omega-6

• Essential fatty acids cannot be made by the body and must be consumed in the diet.
• Omega-6 (linoleic acid) is common in nuts, seeds, vegetable oils, and poultry.
• Omega-3 includes plant-based (linolenic acid in chia/flax/walnuts/canola oil) and marine sources (EPA/DHA in fatty fish and omega-3 eggs).
• Marine omega-3s are more bioavailable than plant omega-3s; plant omega-3s must be ground (like flaxseed) and not overheated.
• General recommendation: eat 8–12 ounces of omega-3-rich fish per week; consider mercury risk in certain fish.

Dietary Fat Recommendations

• Recommended fat intake is 20–35% of daily calories.
• Less than 10% of calories should come from saturated fat; minimize trans fat intake.
• Omega-6 recommended at 17g/day (men) and 12g/day (women); omega-3 at 1.6g/day (men) and 1.1g/day (women).

Sources of Saturated Fat

• Major sources: mixed dishes (e.g., pizza, burgers), dairy (cream, cheese, whole milk), fatty meats, snacks/sweets, and tropical oils (coconut, palm).
• Leaner meats, plant-based proteins, and low-fat/nonfat dairy can reduce saturated fat intake.

The Mediterranean Diet

• Traditional diet high in olive oil, whole grains, fruits, veggies, legumes, nuts, and low in added sugar and animal foods.
• Modern Mediterranean diet emphasizes unsaturated fats, plant-based foods, fish, and limits red meat, dairy, eggs, added sugar, and processed foods.

Lipoproteins and Heart Disease Risk

• Lipoproteins carry fats through watery blood; types include chylomicrons, VLDL, LDL, and HDL.
• LDL (low-density) delivers cholesterol to tissues; high levels increase heart disease risk ("bad cholesterol").
• HDL (high-density) removes excess cholesterol; high levels are protective ("good cholesterol").
• Saturated and trans fats increase LDL; mono- and polyunsaturated fats lower LDL.
• Food cholesterol has minimal impact on blood cholesterol for most people.
• Physical activity raises HDL and improves heart and glucose regulation.

Key Terms & Definitions

• Hydrogenation — Process of adding hydrogen to oils, making them solid.
• Cis Fatty Acid — Unsaturated fatty acid with hydrogens on the same side of the double bond.
• Trans Fatty Acid — Unsaturated fatty acid with hydrogens on opposite sides; harmful if artificially produced.
• Lipoprotein — Combination of lipid and protein that transports fat through blood.
• LDL (Low-Density Lipoprotein) — "Bad" cholesterol carrier; high levels increase heart disease risk.
• HDL (High-Density Lipoprotein) — "Good" cholesterol carrier; high levels reduce heart disease risk.
• Omega-3/Omega-6 — Essential polyunsaturated fatty acids required in the diet.

Action Items / Next Steps

• Review food labels for hydrogenated oils and saturated fat content.
• Consume ground flaxseed or chia seeds for plant-based omega-3s.
• Prioritize fish high in EPA/DHA for omega-3s; avoid high-mercury varieties if pregnant or a child.
• Aim for a balanced fat intake as per AMDR and Dietary Guidelines.
• Prepare for further discussion on heart disease and its relation to dietary fats.