Fat Words

by Eleanor Mayfield

Here are brief definitions of the key terms important to an understanding of the role of fat in the diet.

Cholesterol: A chemical compound manufactured in the body. It is used to build cell membranes and brain and nerve tissues. Cholesterol also helps the body make steroid hormones and bile acids.
Dietary cholesterol: Cholesterol found in animal products that are part of the human diet. Egg yolks, liver, meat, some shellfish, and whole-milk dairy products are all sources of dietary cholesterol.
Fatty acid: A molecule composed mostly of carbon and hydrogen atoms. Fatty acids are the building blocks of fats.
Fat: A chemical compound containing one or more fatty acids. Fat is one of the three main constituents of food (the others are protein and carbohydrate). It is also the principal form in which energy is stored in the body.
Hydrogenated fat: A fat that has been chemically altered by the addition of hydrogen atoms (see trans fatty acid). Vegetable shortening and margarine are hydrogenated fats.
Lipid: A chemical compound characterized by the fact that it is insoluble in water. Both fat and cholesterol are members of the lipid family.
Lipoprotein: A chemical compound made of fat and protein. Lipoproteins that have more fat than protein are called low-density lipoproteins (LDLs). Lipoproteins that have more protein than fat are called high-density lipoproteins (HDLs). Lipoproteins are found in the blood, where their main function is to carry cholesterol.
Monounsaturated fatty acid: A fatty acid that is missing one pair of hydrogen atoms in the middle of the molecule. The gap is called an "unsaturation." Monounsaturated fatty acids are found mostly in plant and sea foods. Olive oil and canola oil are high in monounsaturated fatty acids. Monounsaturated fatty acids tend to lower levels of LDL-cholesterol in the blood.
Polyunsaturated fatty acid: A fatty acid that is missing more than one pair of hydrogen atoms. Polyunsaturated fatty acids are mostly found in plant and sea foods. Safflower oil and corn oil are high in polyunsaturated fatty acids. Polyunsaturated fatty acids tend to lower levels of both HDL-cholesterol and LDL-cholesterol in the blood.
Saturated fatty acid: A fatty acid that has the maximum possible number of hydrogen atoms attached to every carbon atom. It is said to be "saturated" with hydrogen atoms. Saturated fatty acids are mostly found in animal products such as meat and whole milk. Butter and lard are high in saturated fatty acids. Saturated fatty acids tend to raise levels of LDL-cholesterol ("bad" cholesterol) in the blood. Elevated levels of LDL-cholesterol are associated with heart disease.
Trans fatty acid: A polyunsaturated fatty acid in which some of the missing hydrogen atoms have been put back in a chemical process called hydrogenation, resulting in "straighter" fatty acids that solidify at higher temperatures. Trans fatty acids are under study to determine their effects on cholesterol.