September 2006September 2006
Dietary fat is a nutrient needed for an overall healthful 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. Fats are composed of the same three elements as carbohydrates namely carbon, hydrogen, and oxygen. Fats have relatively more carbon and hydrogen and less oxygen, thus accounting for the higher energy value.
Dietary fat supplies essential fatty acids, linoleic and linolenic acids, which are especially important to children for proper growth. In addition, fat is required for maintenance of healthy skin, for regulation of cholesterol metabolism, and as a precursor of prostaglandins, hormone-like substances that regulate many body functions. It is also needed to carry and aid in the absorption of fat-soluble vitamins A, D, E, and K and carotenoids. The largest amount of fat is stored in the body’s adipose (fat) cells but, some fat is found in blood plasma and other body cells. These fat deposits not only store energy, but also are important in insulating the body and supporting and cushioning organs.
Saturated and Unsaturated Fats
The 2005 Dietary Guidelines for Americans recommend that healthy people consume less than 10 percent of calories from saturated fats daily. Meats, baked goods, and full-fat dairy products are the main sources of saturated fats in most diets. Coconut, palm, and palm kernel oils also contain saturated fats.
Monounsaturated and polyunsaturated fatty acids are unsaturated fats. When they replace saturated fats in the diet, they help reduce blood cholesterol levels and thus lower the risk of heart disease. The 2005 Dietary Guidelines for Americans recommend keeping total fat intake between 20 and 35 percent of calories with most fats coming from sources of polyunsaturated and monounsaturated fatty acids such as fish, nuts, and vegetable oils. Canola, olive, peanut, high oleic safflower and sunflower oils, and nuts are rich in monounsaturated fats. Sources of alpha-linolenic and linoleic acids, which are unsaturated fats and essential, include vegetable oils, walnuts, and flaxseed.
Moderating Dietary Fat
The 2005 Dietary Guidelines for Americans recommend a total fat intake between 20 and 35 percent of calories for adults to meet daily energy and nutritional needs while minimizing risk of chronic disease. In 2002, The Institute of Medicine (IOM) recommended that the intake of saturated fats be less than 10 percent of calories, cholesterol be less than 300 mg/day, and trans fatty acid consumption be as low as possible. Consumption of certain fatty acids are encouraged because of their positive health effects, which are explored in-depth in the Functional Foods section of IFIC.org. The U.S. Department of Agriculture’s MyPyramid food guidance system recommends oils from foods such as vegetable oils, nuts, and some fish because of their healthful attributes.
The challenge is in consuming lower amounts of trans fats, as well as lower amounts of saturated fats. The FDA, after evaluation of research on two fatty acids, released two qualified health claims for EPA/DHA and olive oil to acknowledge their possible beneficial effects of reducing the risk of coronary heart disease. Ultimately, weight management is dependent on balancing the number of calories consumed with the number of calories expended.
Links and Resources
United States Department of Health and Human Services (DHHS)
Dietary Guidelines for Americans 2005
United States Department of Agriculture (USDA)
MyPyramid.gov Food Guidance System