Our knowledge of the roles and functions of fats is evolving. For the past several decades, healthful eating has been equated with low-fat eating. For many, this has meant avoiding or eliminating foods with fats. But there’s more to healthful eating than simply cutting back on fats. The latest edition of
Dietary Guidelines for Americans recommends choosing “a diet that is low in saturated fat and cholesterol and moderate in total fat.” These national guidelines are striving to change the outdated and oversimplified belief that fats are harmful to health.
Experts no longer simply recommend a diet low in total fat. Instead, there is greater emphasis on reducing intake of saturated fat and cholesterol. Therefore, less emphasis on a diet low in total fat intake translates to a diet moderate in total fat. Evidence is also unfolding that the type of fat you eat may be just as important or even more important than the total amount of fat in your diet because it has become clear that the distinct types of fats in foods have different effects on health. Some fats may even offer benefits to your health. Therefore, it makes sense to moderate, not eliminate, your intake of fats.
Types of Fats
Although the fat in food is often referred to as a single substance, there is no one type of fat. All fats are composed of fatty acids, which are the building blocks of fat. The attributes of fats—how they function in foods and how they affect health—are determined by the amounts and mixtures of fatty acids.
Individual fatty acids may be saturated, monounsaturated, or polyunsaturated. They differ primarily in the amount of hydrogen they contain. Saturated fatty acids contain the most hydrogen—that is, they are “saturated” with hydrogen. Polyunsaturated fatty acids contain the least amount of hydrogen.
The relative amounts of saturated and unsaturated fatty acids determine whether fats are solid or liquid. Fats with larger amounts of saturated fatty acids are typically more solid, such as butter or the visible fat on meats. Oils are a liquid form of fat and contain larger amounts of unsaturated fatty acids, which are liquid at room temperature.
Saturated fatty acids are mainly found in animal foods, including meat, poultry, butter, and whole-milk dairy products. Unlike other oils, tropical vegetable oils, including coconut, palm kernel, and palm oils, contain mostly saturated fatty acids.
Polyunsaturated fatty acids are found in plant foods, as well as fish and seafood. Plant sources include corn, safflower, sunflower, and sesame oils, as well as some nuts and seeds.
Monounsaturated fatty acids are found in plant foods such as canola, peanut, and olive oils, as well as nuts and avocados. The fat in meats, including beef, pork, and poultry, is composed of almost equal amounts of monounsaturated and saturated fatty acids.
Trans fats are present in variable amounts in a wide range of foods, including most foods made with partially hydrogenated oils, such as baked goods and fried foods, and some margarine products. Through hydrogenation, unsaturated fatty acids can be made more saturated. This converts a liquid fat into a more stable liquid or semisolid form, resulting in the formation of trans fatty acids. Trans fats also occur naturally in low amounts in meats and dairy products.
In the body, fats are essential for life. Although various types of fats have different effects in the body, the best advice is to moderate, not eliminate, the amount of fats in your diet. Enjoy the appealing qualities of fats by balancing higher-fat items with lower-fat choices, such as grains, vegetables, fruits, dairy products, and lean meats and meat alternatives. Strive for the majority of fat that you consume to be polyunsaturated and monounsaturated fat, while reducing the amount of saturated fat and trans fat that you consume.
