HE-435, November 1996. Recommended for Extension use by Barbara Struempler, Extension Nutritionist, Professor, Nutrition and Food Science, Auburn University. Originally prepared by J. Yvonne Jackson, former Nutrition Specialist.

Fats & Cholesterol

SECTIONS

I. Fats

II. Cholesterol

III. The Controversy

IV. References

Calorie, Fat, And Cholesterol Content Table

I. Fats

Fats are vital to the normal functioning of the body. They provide an essential fatty acid, linoleic acid, which is needed for growth. Fats are the carriers for the fat-soluble vitamins A, D, E, and K. During digestion, fat must be present so these vitamins can be absorbed and used in the body.

Fats also are very important energy sources. They provide 9 calories for each gram of fat. This is at least twice as many calories as you get from either carbohydrates or proteins.

Much of the flavor of foods is provided by fats. The body digests fats slowly, and they stay in the stomach longer to keep you from feeling hungry, providing satiety, or a feeling of fullness.

How Much Fat Do You Need?
The body makes some fatty acids. The ones the body cannot make are called essential fatty acids and must come from food. Most food fats are triglycerides. A triglyceride is three acids attached to glycerol, a common chemical compound.

The amount of fat in food varies. Vegetable oil is 100 percent fat. Butter and margarine are 80 percent fat and 20 percent water and milk solids. Other concentrated fats are lard, shortening, bacon, and fat back. These fats are easily recognized. The less visible fats are the ones that tend to cause people to eat too much fat. These foods include some meats, eggs, milk, cheese, ice cream, nuts, peanut butter, bakery products, potato chips, and many processed foods.

It has not been determined exactly how much fat a person should eat. A reasonable level for total fat in the diet for a healthy person is about 30 percent of the total calories needed.

Saturated And Unsaturated Fats
There are two major types of dietary fat saturated and unsaturated. Unsaturated fats are further classified as either polyunsaturated or monounsaturated fats. Together, saturated and unsaturated fats equal total fat. All foods containing fat contain a mixture of these fats.

Saturated fat raises your blood cholesterol level more than anything else in your diet. Some of the best ways to reduce the amount of saturated fat that you eat are to trim meats of fat, use low-fat dairy products such as milk and cheese, and eat moderate amounts of meats.

Animal products as a group are a major source of saturated fat in the average American diet. Butter, cheese, whole milk, cream, and ice cream all contain high amounts of saturated fat. Saturated fat is also concentrated in the fat that surrounds meat and in the white streaks of fat in the muscle of meat (marbling). Poultry, fish, and shellfish also contain saturated fat, although generally less than meat.

Unsaturated fat actually helps to lower cholesterol levels when it is substituted for saturated fat. Therefore, health professionals recommend that you substitute unsaturated fats (polyunsaturated and monounsaturated fats) for part of any saturated fat whenever possible.

Polyunsaturated fats are found primarily in safflower, corn, soybean, cottonseed, sesame, and sunflower oils, which are common cooking oils. Polyunsaturated fats are also contained in most salad dressings.

Olive and canola oil (rapeseed oil) are examples of oils that are high in monounsaturated fats. Like other vegetable oils, these oils are used in cooking as well as in salads. Recent research shows that substituting monounsaturated fat (like substituting polyunsaturated fat) for saturated fat reduces blood cholesterol levels.

The terms saturated and unsaturated refer to the chemical structure-of the fatty acids. Hydrogenation is a process of adding hydrogen to change a liquid oil to a more solid form for margarines and shortenings. Hydrogenation changes polyunsaturated fatty acids into more saturated fatty acids. The margarines highest in polyunsaturates have liquid vegetable oil listed as the first ingredient. The next ingredient will be hydrogenated or partially hydrogenated vegetable oil. If these oils are listed in reverse, the margarine is not as high in polyunsaturates.

II. Cholesterol

Cholesterol is essential for forming the protective covering of nerve cells. It is important to the building of hormones, and it is a part of the formation of vitamin D.

Cholesterol has received a great deal of attention since researchers found that the amount of cholesterol in the blood stream is a good indication of your risk of heart disease. The higher your blood cholesterol, the higher your risk of having heart disease. Much of the blood cholesterol is made in the body.

Dietary cholesterol comes only from animal products; this includes not only the meat of animals but also crab, shrimp, lobster, and animal products such as milk, egg yolk, butter, and lard. Plants do not make cholesterol. Therefore, foods made from plants have no cholesterol unless animal products have been added during processing or preparation.

Cholesterol and other fat (lipid) substances are carried in the blood attached to protein. This combination is called a lipoprotein -- lipid + protein. There are many types of lipoproteins. High-density lipoproteins (HDL) are the ones responsible for carrying cholesterol in the blood stream.

III. The Controversy

There is little dispute over the fact that your diet influences your levels of blood cholesterol, lipoprotein, and triglycerides.

• Eating foods with saturated fats increases your blood level of both cholesterol and triglycerides.
• Eating foods high in cholesterol increases your blood cholesterol level.

The controversy concerns just how important this really is. The only relationship between diet and heart disease that researchers seem to agree on unanimously is that overweight increases risk of heart disease. There is strong evidence that weight control is the best protection against heart disease. However, the incidence of heart disease in the United States is decreasing. And, while the exact reasons are unknown, contributing factors seem to be that people are eating fewer foods with high levels of saturated fats and cholesterol and are eating more polyunsaturated fats. The USDA Dietary Guidelines for Americans suggest that you limit fats, saturated fat, and cholesterol in your diet and and that you maintain a healthy weight.

Researchers have now found that the level of high-density lipoprotein (HDL) in the blood may be a better predictor of heart disease than blood cholesterol. HDLs remove cholesterol from body tissues and prevent its buildup. Therefore, the higher your blood level of HDL, the less risk of your developing heart disease. Factors leading to the development of HDLs include maintaining normal weight, controlling the fat and calories in your diet, exercising, not smoking, and reducing alcohol consumption.

It's important to remember that diet is only one of the many risk factors associated with cardiovascular diseases. Others are heredity, your age and sex, smoking, exercise, overweight, blood pressure, and diseases such as diabetes.

Calorie, Fat, And Cholesterol Content Table

IV. References

Diet and Health: Implications for Reducing Chronic Disease Risk. 1989. National Research Council, National Academy Press, Washington, D.C.

Eating to Lower Your High Blood Cholesterol. 1987. U.S. Department of Health and Human Services, NIH Publication No. 87-2920, Bethesda, MD 20892.

Ernst, Nancy D., et al. 1988. The National Cholesterol Education Program: Implications for dietetic practitioners from the Adult Treatment Panel Recommendations. Journal of the American Dietetic Association 88:1401-11.

Kris-Etherton, P. M. et al. 1988. The effect of diet on plasma lipids, lipoproteins and coronary heart disease. Journal of the American Dietetic Association, 88:1373-1400.

Nutrition and Your Health: Dietary Guidelines for Americans. 1990. USDA and HEW. Recommended Dietary Allowances. 1989. 10th ed., National Research Council, National Academy Press, Washington, D.C.

The Surgeon General's Report on Nutrition and Health. 1988. U.S.Department of Health and Human Services, Public Health Service, DHHS Publication No. 88-50210, Washington, D.C.

Calorie, Fat, And Cholesterol Content Table