Understanding the different types of fats can be difficult for the consumer. Since not all fats are created equal in health, it is important to understand the differences in dietary fats; healthy versus unhealthy.

Triglycerides (triacylglycerols) are an important class of dietary fats. The triglyceride consists of a molecule of glycerol and three molecules of fatty acids. Biologic properties of triglycerides are determined by the presence or absence of double bonds, the number and location of double bonds, and the configuration (cis, trans) of the unsaturated fatty acid. Fatty acids consist of a hydrocarbon chain (C-H) with a carboxyl group (COOH) at one end. The glycerol molecule contains three hydroxyl groups (OH).

Much of the fat in the body is in the form of triglycerides. Many of the foods we eat also contain triglycerides. Elevated triglyceride levels in the blood have been linked to an increased risk of heart disease. These triglycerides are not directly from dietary fats but made in the liver from excess sugars that have not been used for energy. The excess sugar source is from foods containing carbohydrates such as refined sugar and white flour.

Saturated fats are a type of triglyceride. This triglyceride contains primarily fatty acids whose side chains do not contain any double bonds. These fats are characteristically called saturated because all available carbon bonds are occupied by a hydrogen atom. Saturated fats are highly stable and can resist oxidation. The saturated fat molecule is straight in form. Hence, saturated fats form a solid or semisolid at room temperature. Main sources of saturated fats are meat and dairy products, and a few vegetable oils (palm and coconut oils). A diet high in saturated fat is associated with an increased risk of heart disease.

Monounsaturated fats are another type of triglyceride. The fatty acids contain only one double bond. A few sources of monounsaturated fats are olive, peanut, and rapeseed (canola) oil. This type of fat has the ability to favorably modify lipoprotein levels. A good example of a diet high in monounsaturated fat is the Mediterranean diet. The Mediterranean cultures show that a diet rich in olive oil is correlated with a low incidence of heart disease.

Polyunsaturated fats are a type of triglyceride in which the fatty acids contain more than one double bond. Double bonds in natural fats are rigid and introduce a kink in the molecule. This kink prevents the fatty acids from packing close together. As a result, unsaturated fats have a lower melting point than saturated fats. Most unsaturated fats are liquid at room temperature and referred to as oils.

The effect that the polyunsaturated fat has on heart disease is influenced by the location of the double bond within the molecule. Omega-6 fatty acids (n-6 fatty acids) are a type of polyunsaturated fat. The omega-6 fatty acid, primarily linoleic acid obtained from vegetable oils protects against heart disease. Good sources of omega-6 fats are nuts, avocados, olives, soybeans, along with sesame, cottonseed, and corn oil.

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