Backgrounder On Fat & Cholesterol Dietary fat is a vital nutrient in a healthy lifestyle. Like carbohydrates and protein, dietary fat is an important source of energy for the body. Fat is the most concentrated source of energy in the diet, providing nine calories per gram compared with four calories per gram from either carbohydrates or protein. Dietary fat supplies essential fatty acids, such as linoleic acid, which is especially important to children for proper growth. Fat also is required for maintenance of healthy skin, regulation of cholesterol metabolism and as a precursor of prostaglandins, hormone-like substances that regulate some body processes. Dietary fat is needed to carry fat-soluble vitamins A, D, E and K and to aid in their absorption from the intestine. It also helps the body use carbohydrate and protein more efficiently. The body uses whatever fat it needs for energy, and the rest is stored in various fatty tissues. Some fat is found in blood plasma and other body cells, but the largest amount is stored in the body's adipose (fat) cells. These fat deposits not only store energy, but also are important in insulating the body and supporting and cushioning organs. Cholesterol, a fat-like substance, also is vital to life. A component of cell membranes, cholesterol is necessary for the production of bile acids, which aid in food digestion, and in the production of sex hormones. An excess of cholesterol in the blood, however, can lead to deposits in the walls of blood vessels and reduce blood flow to major arteries. Dietary Fat & Cholesterol Technically, fats should be referred to in the plural, as there is no one type of fat. Fats are composed of the same three elements as carbohydrates: carbon, hydrogen and oxygen. However, fats have relatively more carbon and hydrogen and less oxygen, thus supplying the higher fuel value of nine calories per gram. Fats are actually combinations of many different fatty acids, each exerting characteristic physiological and metabolic effects. These fatty acids are generally classified as saturated, monounsaturated or polyunsaturated. These terms refer to the number of hydrogen atoms attached to the carbon atoms of the acid chains in the fat molecule. Saturated fatty acids are more stable than unsaturated fatty acids because of their chemical structure. Stability is especially important in cooking oil to prevent rancidity and off flavors or odors. Fat is an important ingredient in many foods because of its functional properties. In many recipes, fat enhances the taste, aroma and texture of the food. Because it is digested more slowly than protein or carbohydrates, it also plays an important role in satiety, providing a sense of fullness after eating. Contrary to popular belief, most of the cholesterol found in the blood is manufactured by the body itself, not derived through foods consumed in the diet. Dietary cholesterol is found only in animal foods such as egg yolks, organ meats, beef, chicken and shellfish. Vegetable oils and shortenings are cholesterol-free. Hydrogenation Because all fats, especially unsaturated fats, have a tendency to breakdown when exposed to air, they are often hydrogenated by food manufacturers for greater stability. Hydrogenation is the process of adding hydrogen molecules directly to an unsaturated fatty acid such a vegetable oil to convert it to a semi-solid form such as margarine. Developed in the early 1900s, hydrogenation contributes important textural properties in food. The degree of hydrogenation can help influence the firmness and spreadability of margarines, flakiness of pie crust and the creaminess of puddings. Hydrogenated oils are sometimes used in place of other fats with higher proportions of saturated fatty acids such as butter. When oils are hydrogenated, certain types of trans fatty acids are formed. Scientists are continuing to study the physiological effects of such trans fatty acids on blood cholesterol levels. Trans fatty acids from all sources provide only two to three percent of calories compared with 14 percent from saturated fat and 36 percent from total fat in the diet. Health Effects An excess of dietary fat has become increasingly recognized as one risk factor influencing the development of chronic disease. Currently, the average intake of fat in the United States is about 36 percent of total calories, a drop of about 5 percent in the last decade. Most health authorities advise that adults limit fat consumption to 30 percent of total calories, with saturated fat providing no more than 10 percent. The main concern about excess fat in the diet centers on its potential role in raising blood cholesterol, a risk factor in the development of coronary heart disease (CHD). Physicians and other health professionals measure the level of blood cholesterol to help determine an individual's risk for CHD. CHD kills more Americans every year than any other disease or group of diseases. The average level of blood cholesterol in Americans is approximately 200-215 milligrams per deciliter (mg/dl). According to the National Institutes of Health, under 200 mg/dl is considered a desirable blood cholesterol level; over 240 mg/dl is considered high total cholesterol. Scientists also have identified individual classes of total blood cholesterol. Low-density lipoprotein (LDL) fractions, referred to as the "bad cholesterol," contain most of the cholesterol in the blood and are associated with cholesterol deposits on artery walls. High-density lipoprotein (HDL) fractions, referred to as the "good cholesterol," is believed to carry cholesterol out of the blood and back to the liver for breakdown and excretion. Thus, having high HDL levels of cholesterol in the blood may be as important as having low LDL levels to reduce the risk of CHD. In addition to diet, blood cholesterol is influenced by a wide variety of factors such as heredity, age, race, sex, high blood pressure, overweight, activity level, diabetes and cigarette smoking. For some people, heredity may be even a stronger predictor of blood cholesterol than diet. Scientists may soon be able to isolate a gene that is carried by such "cholesterol responsive" individuals and apply early intervention through drug therapy and other means. Moderating Dietary Fat According to the National Research Council's 1988 Designing Foods report, 58 percent of the total fat and 75 percent of the saturated fat in the average U.S. diet is derived from animal sources. Primary animal sources of fat include red meats, poultry and fish; milk and milk products; and eggs. In addition to direct consumption of meat products, fat is consumed in fried foods and other products such as butter, margarine, dairy products, cheese, nuts, baked goods, salad oils, shortenings, mayonnaise, salad dressings, frostings, gravies and sauces. To help Americans moderate their dietary fat intake, producers have developed a wide variety of reduced-fat food products. Low-fat meats are more common as producers select leaner, meatier animals for market and butchers trim away more fat. Low-fat and skim milk outsell whole milk, and choices in reduced-fat cheeses, sour cream, butter, margarine, yogurt and other spreads are increasing. In addition, snack foods, cakes, pastries and frozen desserts are available in reduced fat and calorie, as well as fat-free varieties. Clearly, consumers have expressed a demand for foods lower in calories and fat. As companies continue to apply their research and development skills to this challenge, a number of innovative products are sure to follow. But moderation in fat and cholesterol consumption is only one aspect of good nutrition. Variety, moderation and balance of all foods is the most prudent approach for the general population. Moreover, a well-balanced diet in combination with plenty of exercise, maintaining proper weight, avoiding smoking and controlling diseases such as hypertension is the best approach to a healthy lifestyle. Reprinted from the International Food Information Council Foundation, 1995

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