Lipids, Triglycerides, Phospholipids, and Sterols (Part 1) PDF

12/4/2023 1 THE LIPIDS: TRIGLYCERIDES, PHOSPHOLIPIDS, AND STEROLS Part1 Dr. Hala Nawaiseh 12/4/2023 2 The Chemist’s View of Fatty Acids and Triglycerides 1. Every triglyceride contains one molecule of glycerol and three f...

12/4/2023 1 THE LIPIDS: TRIGLYCERIDES, PHOSPHOLIPIDS, AND STEROLS Part1 Dr. Hala Nawaiseh 12/4/2023 2 The Chemist’s View of Fatty Acids and Triglycerides 1. Every triglyceride contains one molecule of glycerol and three fatty acids (basically, chains of carbon atoms). 2. Fatty acids may be 4 to 24 (even numbers of) carbons long, the 18-carbon ones being the most common in foods and especially noteworthy in nutrition. 3. Fatty acids may be saturated or unsaturated. Unsaturated fatty acids may have one or more points of unsaturation that is, they may be monounsaturated or polyunsaturated. 12/4/2023 3 The Chemist’s View of Fatty Acids and Triglycerides 4. Of special importance in nutrition are the polyunsaturated fatty acids known as omega-3 fatty acids and omega-6 fatty acids. The 18-carbon polyunsaturated fatty acids are: linolenic acid (omega-3) linoleic acid (omega-6). Both are essential fatty acids that the body cannot make. Lipids: A family of compounds that includes triglycerides, phospholipids, and sterols. Lipids are characterized by their insolubility in water. (include the fat-soluble vitamins). 12/4/2023 4 Fatty Acids All fatty acids have the same basic structure—a chain of carbon and hydrogen atoms with an acid group (COOH) at one end and a methyl group (CH3) at the other end. Fatty acids may differ from one another in the: Length of their carbon chains. The number and location of their double bonds. 12/4/2023 5 Fatty Acids The Length of the Carbon Chain Most naturally occurring fatty acids contain even numbers of carbons in their chains up to 24 carbons in length. Stearic acid is the simplest of the 18-carbon fatty acids; the bonds between its carbons are all alike: 12/4/2023 6 Fatty Acids 12/4/2023 7 Fatty Acids 12/4/2023 8 Fatty Acids Fatty acids: Organic compounds composed of a carbon chain with hydrogens attached and an acid group (COOH) at one end and a methyl group (CH3 ) at the other end. Monounsaturated fatty acid (MUFA) : A fatty acid that lacks two hydrogen atoms and has one double bond between carbons; Examples include palmitoleic acid and oleic acid. 12/4/2023 9 Fatty Acids Polyunsaturated fatty acid:( PUFA) A fatty acid that lacks four or more hydrogen atoms and has two or more double bonds between carbons. Examples include linoleic acid (two double bonds) and linolenic acid (three double bonds). Saturated fatty acid: A fatty acid carrying the maximum possible number of hydrogen atoms. Example, stearic acid. 12/4/2023 10 Fatty Acids Saturated fatty acid: The Number of Double Bonds Stearic acid is a saturated fatty acid. A saturated fatty acid is fully loaded with all its hydrogen atoms and contains only single bonds between its carbon atoms 12/4/2023 11 Fatty Acids A polyunsaturated fatty acid has two or more carbon-to- carbon double bonds. Linoleic acid, the 18-carbon fatty acid common in vegetable oils, lacks four hydrogens and has two double bonds: 12/4/2023 12 Fatty Acids 12/4/2023 13 Fatty Acids The Location of Double Bonds Fatty acids differ not only in the length of their chains and their degree of saturation, but also in the locations of their double bonds. Chemists identify polyunsaturated fatty acids by the position of the double bond closest to the methyl (CH3) end of the carbon chain, which is described by an omega number. A polyunsaturated fatty acid with its closest double bond three carbons away from the methyl end is an omega-3 fatty acid. An omega-6 fatty acid is a polyunsaturated fatty acid with its closest double bond six carbons away from the methyl end. 12/4/2023 14 Omega-3 and Omega-6 Fatty Acids Compared 12/4/2023 15 Fatty Acids Monounsaturated fatty acids tend to belong to the omega- 9 group, with their closest (and only) double bond nine carbons away from the methyl end. Oleic acid—the 18-carbon monounsaturated fatty acid common in olive oil mentioned earlier—is an omega-9 fatty acid. 12/4/2023 16 Triglycerides Triglycerides : The chief form of fat in the diet and the major storage form of fat in the body; composed of a molecule of glycerol with three fatty acids attached. Few fatty acids occur free in foods or in the body. Most often, they are incorporated into triglycerides—lipids composed of three fatty acids attached to a glycerol.* 12/4/2023 17 Triglycerides Glycerol: An alcohol composed of a three-carbon chain, which can serve as the backbone for a triglyceride. 12/4/2023 18 Triglycerides To make a triglyceride, a series of condensation reactions combine a hydrogen atom (H) from the glycerol and a hydroxyl (OH) group from a fatty acid, forming a molecule of water (H2O) and leaving a bond between the two molecules (see the left side of Figure 5-3). Most triglycerides contain a mixture of more than one type of fatty acid (as shown on the right side of Figure 5-3). 12/4/2023 19 Triglycerides 12/4/2023 20 Characteristics of Solid Fats and Oils Condensation: a chemical reaction in which water is released as two molecules combine to form one larger product. Fats: lipids that are solid at room temperature (77ºF, or 25ºC). Oils: lipids that are liquid at room temperature (77ºF, or 25ºC). Oxidation : The process of a substance combining with oxygen; oxidation reactions involve the loss of electrons. Antioxidants: As a food additive, preservatives that delay or prevent rancidity of fats in foods and other damage to food caused by oxygen. 12/4/2023 21 Characteristics of Solid Fats and Oils Firmness: The degree of unsaturation influences the firmness of fats at room temperature. Most polyunsaturated vegetable oils are liquid at room temperature, and the more saturated animal fats are solid. Cocoa butter, palm oil, palm kernel oil, and coconut oil are saturated; they are firmer than most vegetable oils because of their saturation, but softer than most animal fats because of their shorter carbon chains (8 to 14 carbons long). The shorter the carbon chain, the softer the fat is at room temperature. 12/4/2023 22 Characteristics of Solid Fats and Oils 12/4/2023 23 Characteristics of Solid Fats and Oils Stability: The degree of unsaturation also influences stability. All fats become spoiled when exposed to oxygen. The oxidation of fats produces a variety of compounds that smell and taste rancid. Exposure to heat and light can also speed up rancidity. Polyunsaturated fats spoil most readily because their double bonds are unstable; monounsaturated fats are slightly less susceptible. 12/4/2023 24 Characteristics of Solid Fats and Oils Hydrogenation: A chemical process by which hydrogens are added to monounsaturated or polyunsaturated fatty acids to reduce the number of double bonds, making the fats more saturated (solid) and more resistant to oxidation (protecting against rancidity). Hydrogenation produces trans-fatty acids. 12/4/2023 25 Characteristics of Solid Fats and Oils Hydrogenation: During hydrogenation, some or all of the points of unsaturation are saturated by adding hydrogen molecules. Hydrogenation offers two food processing advantages: It protects against oxidation (thereby prolonging shelf life) by making polyunsaturated fats more saturated. It alters the texture of foods by making liquid vegetable oils more solid. 12/4/2023 26 Characteristics of Solid Fats and Oils Double bonds in a polyunsaturated fatty acid carry a slightly negative charge and readily accept positively charged hydrogen atoms, creating a saturated fatty acid. Most often, fat is partially hydrogenated, creating a trans-fatty acid 12/4/2023 27 Characteristics of Solid Fats and Oils Trans-Fatty Acids: In nature, most double bonds are Cis meaning that the hydrogens next to the double bonds are on the same side of the carbon chain. Only a few fatty acids (notably a small percentage of those found in milk and meat products) naturally occur as Trans- fatty acids meaning that the hydrogens next to the double bonds are on opposite sides of the carbon chain. In the body, trans-fatty acids behave more like saturated fats, increasing blood cholesterol and the risk of heart disease a major health disadvantage. 12/4/2023 28 Characteristics of Solid Fats and Oils Cis: on the near side of; refers to a chemical configuration in which the hydrogen atoms are located on the same side of a double bond. Trans: on the other side of; refers to a chemical configuration in which the hydrogen atoms are located on opposite sides of a double bond. 12/4/2023 29 The Chemist’s View of Phospholipids and Sterols Phospholipids: Lecithin. lecithin has one glycerol with two of its three attachment sites occupied by fatty acids like those in triglycerides. The third site is occupied by a phosphate group and a molecule of choline. The hydrophobic fatty acids make phospholipids soluble in fat; the hydrophilic phosphate group allows them to dissolve in water. Such versatility enables the food industry to use phospholipids as an emulsifier to mix fats with water in such products as mayonnaise, salad dressings, and candy bars. 12/4/2023 30 The Chemist’s View of Phospholipids and Sterols 12/4/2023 31 The Chemist’s View of Phospholipids and Sterols Phospholipids in Foods In addition to the phospholipids used by the food industry as emulsifiers, phospholipids are also found naturally in foods. The richest food sources of lecithin are eggs, liver, soybeans, wheat germ, and peanuts. 12/4/2023 32 The Chemist’s View of Phospholipids and Sterols Roles of Phospholipids: Lecithin and other phospholipids are constituents of cell membranes. Phospholipids are soluble in both water and fat, they can help fat-soluble substances, including vitamins and hormones, to pass easily in and out of cells. Phospholipids also act as emulsifiers in the body, helping to keep fats suspended in the blood and body fluids. 12/4/2023 33 The Chemist’s View of Phospholipids and Sterols Roles of Phospholipids 12/4/2023 34 The Chemist’s View of Phospholipids and Sterols Sterols Compounds containing a four-ring carbon structure with any of a variety of side chains attached. Cholesterol : one of the sterols containing a four-ring carbon structure with a carbon side chain. 12/4/2023 35 12/4/2023 36 The Chemist’s View of Phospholipids and Sterols Roles of Sterols: Many vitally important body compounds are sterols. Among them are bile acids. Sex hormones (such as testosterone, androgen, and estrogen). Adrenal hormones (such as cortisol, cortisone, and aldosterone). Vitamin D, as well as cholesterol itself. 12/4/2023 37 The Chemist’s View of Phospholipids and Sterols The chemical structure is the same, but cholesterol that is made in the body is referred to as endogenous, whereas cholesterol from outside the body (from foods) is referred to as exogenous. Liver is manufacturing cholesterol from fragments of carbohydrate, protein, and fat. The liver makes about 800 to 1500 milligrams/ day. The Daily Value on food labels for cholesterol is 300 milligrams/day. 12/4/2023 38 The Chemist’s View of Phospholipids and Sterols Cholesterol’s harmful effects in the body occur when it accumulates in the artery walls and contributes to the formation of plaque. These plaque deposits lead to atherosclerosis, a disease that causes heart attacks and strokes. 12/4/2023 39 Digestion, Absorption, and Transport of Lipids The goal of fat digestion is to dismantle triglycerides into small molecules that the body can absorb and use , (monoglycerides, fatty acids, and glycerol). In the Mouth: Fat digestion starts off slowly in the mouth, with some hard fats melting as they reach body temperature. A salivary gland at the tongue releases an enzyme (lingual lipase) that plays an active role in fat digestion in infants, but a relatively minor role in adults. 12/4/2023 40 Digestion, Absorption, and Transport of Lipids In the Stomach: In a quiet stomach, fat would float as a layer above the watery components of swallowed food. But whenever food is present, the stomach is active. The strong muscle contractions of the stomach propel its contents toward the pyloric sphincter. Some chyme passes through the pyloric sphincter periodically, but the remaining partially digested food is propelled back into the body of the stomach. 12/4/2023 41 Digestion, Absorption, and Transport of Lipids This churning grinds the solid pieces to finer particles, mixes the chyme with gastric secretions, and disperses the fat into small droplets. These actions help to expose the fat for attack by the gastric lipase enzyme. Little fat digestion takes place in the stomach; most of the action occurs in the small intestine. 12/4/2023 42 Digestion, Absorption, and Transport of Lipids 12/4/2023 43 Digestion, Absorption, and Transport of Lipids In the Small Intestine: When fat enters the small intestine, it triggers the release of the hormone cholecystokinin (CCK), which signals the gallbladder to release its stores of bile. Among bile’s many ingredients are bile acids, which are made in the liver from cholesterol and have a similar structure Bile acids often pair up with an amino acid (a building block of protein 12/4/2023 44 Digestion, Absorption, and Transport of Lipids In the Small Intestine: Most of the hydrolysis of triglycerides occurs in the small intestine. The major fat-digesting enzymes are pancreatic lipases; some intestinal lipases are also active. Enzymes remove all three fatty acids, leaving a free molecule of glycerol. Most sterols can be absorbed as is; if any fatty acids are attached, they are first hydrolyzed off. 12/4/2023 45 12/4/2023 46 Lipid Absorption Small molecules (glycerol and short- and medium-chain fatty acids) can diffuse easily into the intestinal cells; they are absorbed directly into the blood stream. Larger molecules (monoglycerides and long-chain fatty acids) are emulsified by bile, forming spherical complexes known as micelles. The micelles diffuse into the intestinal cells, where the monoglycerides and long-chain fatty acids are reassembled into new triglycerides. 12/4/2023 47 Lipid Absorption The newly made triglycerides and other lipids (cholesterol and phospholipids) are packaged with proteins to make transport vehicles known as chylomicrons. The intestinal cells carefully regulate the production and release of the chylomicrons into the lymphatic system. The blood carries these lipids to the rest of the body for immediate use or storage. 12/4/2023 48 Sizes and Compositions of the Lipoproteins 12/4/2023 49 Lipid Transport Chylomicrons The chylomicrons are the largest and least dense of the lipoproteins. They transport diet-derived lipids (mostly triglycerides) from the small intestine (via the lymph system) to the rest of the body. Within 14 hours after absorption, most of the triglycerides have been depleted, and only a few remnants of protein, cholesterol, and phospholipid remain. Special protein receptors on the membranes of the liver cells recognize and remove these chylomicron remnants from the blood. 12/4/2023 50 Lipid Transport VLDL lipids made in the liver and those collected from chylomicron remnants are packaged with proteins as a VLDL (very-low- density lipoproteins) and shipped to other parts of the body. As the VLDL travel through the body, cells remove triglycerides, causing the proportion of lipids to shift. Cholesterol becomes the predominant lipid, and the lipoprotein becomes smaller and more dense. As this occurs, the VLDL become LDL (low-density lipoproteins), loaded with cholesterol, but containing relatively few triglycerides. 12/4/2023 51 Lipid Transport LDL (Low-Density Lipoproteins) The LDL circulate throughout the body, making their contents available to the cells of all tissues—muscles (including the heart muscle), fat stores, the mammary glands, and others. The cells take triglycerides, cholesterol, and phospholipids to use for energy, make hormones or other compounds, or build new membranes. Special LDL receptors on the liver cells play a crucial role in the control of blood cholesterol concentrations by removing LDL from circulation. 12/4/2023 52 Lipid Transport HDL (High-Density Lipoproteins) The liver makes HDL (high-density lipoproteins) to remove cholesterol from the cells and carry it back to the liver for recycling or disposal. By efficiently clearing cholesterol, HDL help prevent plaque buildup, thereby lowering the risk of heart disease. HDL have antiinflammatory properties that seem to keep artery-clogging plaque from breaking apart and causing heart attacks. 12/4/2023 53 Health Implications The distinction between LDL and HDL has implications for the health of the heart and blood vessels. The blood lipid linked most directly to heart disease is LDL cholesterol. HDL also carry cholesterol, but elevated HDL represent cholesterol returning from the rest of the body to the liver for breakdown and excretion. The transport of cholesterol from the tissues back to the liver is sometimes called reverse cholesterol transport or the scavenger pathway. 12/4/2023 54 Health Implications The following factors help lower LDL and/or raise HDL: Weight control Monounsaturated or polyunsaturated, instead of saturated, fat in the diet Soluble dietary fibers Phytochemicals Moderate alcohol consumption Physical activity 12/4/2023 55 Health Effects and Recommended Intakes of Saturated Fats, Trans Fats, and Cholesterol Cardiovascular disease (CVD) Diseases of the heart and blood vessels throughout the body. Atherosclerosis is the main cause of CVD. When the arteries that carry blood to the heart muscle become blocked, the heart suffers damage known as coronary heart disease (CHD) 12/4/2023 56 Health Effects and Recommended Intakes of Saturated Fats, Trans Fats, and Cholesterol Heart Disease Elevated LDL cholesterol is a major risk factor for cardiovascular disease (CVD). As LDL cholesterol accumulates in the arteries, blood flow becomes restricted and blood pressure rises. Heart disease is the nation’s number-one killer of adults. LDL cholesterol is often used to predict the likelihood of a person’s suffering a heart attack or stroke. 12/4/2023 57 Health Effects and Recommended Intakes of Saturated Fats, Trans Fats, and Cholesterol The more saturated fat in the diet, the more LDL cholesterol in the blood. Not all saturated fats have the same cholesterol- raising effect, Most notable among the saturated fatty acids that raise blood cholesterol are lauric, myristic, and palmitic acids (12, 14, and 16 carbons, respectively). Stearic acid (18 carbons) seems to have little or no effect on blood cholesterol. In addition to raising blood cholesterol, saturated fatty acids contribute to heart disease by promoting blood clotting. 12/4/2023 58 Health Effects and Recommended Intakes of Saturated Fats, Trans Fats, and Cholesterol Fats from animal sources (meats, milk, and milk products) are the main sources of saturated fats in most people’s diets. Selecting lean cuts of meat, skinless poultry, and fat-free milk products helps lower saturated fat intake and the risk of heart disease. Research also suggests an association between dietary trans fats and heart disease. Limiting the intake of trans fats can improve blood cholesterol and lower the risks of heart disease and all-cause mortality. 12/4/2023 59 Health Effects and Recommended Intakes of Saturated Fats, Trans Fats, and Cholesterol Cancer Dietary fat does not seem to initiate cancer development but, instead, may promote cancer once it has arisen. Stronger risk factors for cancer include smoking, alcohol, and environmental contaminants The relationship between dietary fat and the risk of cancer differs for various types of cancers. The increased risk in cancer from fat appears to be due primarily to saturated fats or dietary fat from meats (which is mostly saturated). Fat from milk or fish has not been implicated in cancer risk. 12/4/2023 60 Health Effects and Recommended Intakes of Saturated Fats, Trans Fats, and Cholesterol Obesity Fat contributes more than twice as many kcalories per gram as either carbohydrate or protein. Because fat boosts energy intake, cutting fat from the diet can be an effective strategy in cutting kcalories. Choosing a fat-free food offers no kcalorie savings. Fat-free frozen desserts, for example, often have so much sugar added that the kcalorie count can be as high as in the regular-fat product. In this case, cutting fat and adding carbohydrate offers no kcalorie savings or weight-loss advantage. 12/4/2023 61 Recommended Intakes of Saturated Fat, Trans Fat, and Cholesterol No RDA or Upper Level has been set for Saturated Fat, and Trans Fat. Instead, the DRI and Dietary Guidelines suggest a diet that provides 20 to 35 percent of the daily energy intake from fat, less than 10 percent of daily energy intake from saturated fat, and as little trans fat as possible. Current dietary guidelines no longer limit consumption of dietary cholesterol to 300 milligrams per day, but instead suggest that individuals eat as little dietary cholesterol as possible while consuming a healthy eating pattern. 12/4/2023 62 Recommended Intakes of Saturated Fat, Trans Fat, and Cholesterol For a 2000-kcalorie diet, 20 to 35 percent represents 400 to 700 kcalories from fat. 12/4/2023 63 Health Effects of Monounsaturated and Polyunsaturated Fats Heart Disease Replacing saturated fats with unsaturated fats reduces LDL cholesterol and lowers the risk of heart disease and related deaths. To replace saturated fats with unsaturated fats, sauté foods in olive oil instead of butter,, snack on mixed nuts instead of potato chips, use avocado instead of cheese on a sandwich, and eat salmon instead of steak. 12/4/2023 64 Health Effects of Monounsaturated and Polyunsaturated Fats Regular consumption of omega-3 fatty acids may help prevent blood clots, protect against irregular heartbeats, improve blood lipids, and lower blood pressure, especially in people with hypertension or atherosclerosis. Other Diseases Limited research suggests that the omega-3 fatty acids of fish may protect against asthma, pancreatitis, and rheumatoid arthritis.30 Omega-3 fats also appear to play a role in improving memory and cognition. 12/4/2023 65 12/4/2023 66 Health Effects and Recommended Intakes of Monounsaturated and Polyunsaturated Fats Recommended Intakes of Monounsaturated and Polyunsaturated Fats The 20 to 35 percent of kcalories from fat recommendation provides for the essential fatty acids linoleic acid and linolenic acid. Adequate Intakes (AI). have been established for these two fatty acids. The DRI suggest that linoleic acid provide 5 to 10 percent of the daily energy intake and linolenic acid 0.6 to 1.2 percent. No DRI have been established for the long-chain omega-3 fatty acids EPA or DHA 12/4/2023 67 Fat Replacers Some foods are made with fat replacers—ingredients that provide some of the taste and texture of fats, but with fewer kcalories. Because the body may digest and absorb some of these fat replacers, they may contribute energy, although significantly less energy than fat’s 9 kcalories / gram. Some fat replacers are derived from carbohydrate, protein, or fat. Carbohydratebased fat replacers are used primarily as thickeners or stabilizers in foods such as soups and salad dressings. 12/4/2023 68 Fat Replacers Protein-based fat replacers provide a creamy feeling in the mouth and are often used in foods such as ice creams and yogurts. Fat-based replacers act as emulsifiers and are heat stable, making them most versatile in shortenings used in cake mixes and cookies. 12/4/2023 69 Fat Replacers Fat replacers offering the sensory and cooking qualities of fats but none of the kcalories are called artificial fats. Example of an artificial fat that has been approved for use in snack foods such as potato chips, crackers, and tortilla chips is olestra. A triglyceride is composed of a glycerol molecule with three fatty acids attached, whereas olestra is made of a sucrose molecule with six to eight fatty acids attached. Enzymes in the digestive tract cannot break the bonds of olestra, so unlike sucrose or fatty acids, olestra passes through the digestive system unabsorbed. 12/4/2023 70 Fat Replacers The FDA’s evaluation of olestra’s safety addressed two questions. First, is olestra toxic?. Second, does olestra affect either nutrient absorption or the health of the digestive tract?. 12/4/2023 71 Calculate a Personal Daily Value for Fat The % Daily Value for fat on food labels is based on 78 grams. To know how your intake compares with this recommendation, you can either count grams until you reach 78 or add the “% Daily Values” until you reach 100 percent. If your energy intake is 2000 kcalories a day. If your energy intake is more or less, you can calculate your personal daily fat allowance in grams. Suppose your energy intake is 1800 kcalories per day and your goal is 30 percent kcalories from fat. Multiply your total energy intake by 30 percent, then divide by 9: 12/4/2023 72 Calculate a Personal Daily Value for Fat 1800 total kcal × 0.30 from fat = 540 fat kcal 540 fat kcal ÷ 9 kcal/g = 60 g fat (In familiar measures, 60 grams of fat is about the same as ²∕³ stick of butter or ¼ cup of oil.) 12/4/2023 73 Understand “% Daily Value” and “% kCalories from Fat” The “% Daily Value” that is used on food labels to describe the amount of fat in a food is not the same as the “% kcalories from fat” that is used in dietary recommendations to describe the amount of fat in the diet. They may appear similar, but their difference is worth understanding. 12/4/2023 74 Understand “% Daily Value” and “% kCalories from Fat” A piece of lemon meringue pie that provides 140 kcalories and 12 grams of fat. Because the Daily Value for fat is 78 grams for a 2000-kcalorie intake, 12 grams represent about 15 percent: 12 g ÷ 78 g = 0.15 0.15 × 100 = 15% The pie’s “% Daily Value” is 15 percent of the day’s fat allowance. 12/4/2023 75 Understand “% Daily Value” and “% kCalories from Fat” Does this food meets recommendations to limit fat to “20 to 35 percent kcalories???? 12/4/2023 76 Understand “% Daily Value” and “% kCalories from Fat” It doesn’t—for two reasons. First, the pie’s 12 grams of fat contribute 108 of the 140 kcalories, for a total of 77 percent kcalories from fat: 12 g fat × 9 kcal/g = 108 kcal 108 kcal ÷ 140 kcal = 77% Second, the “percent kcalories from fat” guideline applies to a day’s total intake, not to an individual food. 12/4/2023 77 Two Meals Compared: Replacing Saturated Fat with Unsaturated Fat Examples of ways to replace saturated fats with unsaturated fats include sautéing vegetables in olive oil instead of butter, garnishing salads with avocado and sunflower seeds instead of blue cheese, and eating salmon instead of steak. each of these meals provides roughly the same number of kcalories and grams of fat, but the one on the left has almost four times as much saturated fat and only half as many omega-3 fatty acids. 12/4/2023 78 12/4/2023 79 THE END