Saturated fatty acids are the main fatty acids found in meat and dairy products. Unsaturated fats are most commonly found in the oils of vegetables, such as avocado, and also in nuts and fish. Unsaturated fats are considered the healthiest dietary fats.

Another classification of fats is the "essential fatty acids". These are the polyunsaturated fatty acids that cannot be produced in the human body and must be obtained from the diet, since they are needed for basic functions in our bodies. Present in every healthy cell of the body, they are critical for normal growth and functioning of the cells, muscles, nerves, and organs. Deficiency of essential fatty acids is linked to a variety of symptoms including rough and scaly skin and dermatitis (omega-6 fatty acid) and scaly and hemorrhagic dermatitis, hemorrhagic follicilitis of the scalp, impaired wound healing and growth retardation (omega-3 fatty acids).

Adequate intakes of essential fatty acids may protect against heart diseases and diabetes (DRI, 2002). It has been estimated that as much as 50% of the American population may consume insufficient quantities of essential fatty acids (Hu et al., 1999).

There are two types of essential fatty acids important to human health – the omega-6 and the omega- 3 fatty acids. The term "omega" refers to the position of the first double bond in the fatty acid, counting from the methyl end (O=C—OH) of the carbon chain. An omega-3 fatty acid has the first double bond on the third carbon atom, and an omega-6 fatty acid has the first double bond on the sixth carbon atom. Omega-3 and omega-6 fatty acids cannot be converted from one form to the other. Both have to be present in the diet in a proper balance for a good health.

The metabolism of omega-6 and omega-3 fatty acids in our bodies requires the same enzymes system, resulting in competition between the two families. An excess of one family of fatty acids (usually omega-6) can interfere with the metabolism of the other (usually omega-3), reducing the production of omega-3-derived long-chain fatty acids, and altering their biological effects (Horrobin and Manku, 1990; Emken, 1995).

For instance, linoleic (C18:2; omega-6) and alpha-linolenic (C18:3; omega-3) fatty acids are both essential to humans. From these fatty acids, enzymes in the body can produce other, longer chain fatty acids such as arachidonic acid (AA, C20:4) omega-6, and docosahexaenoic acid (DHA, 22:6) and eicosapentaenoic acid (EPA, C20:5) omega-3, respectively. These two fatty acids work together in a competitive balance to regulate blood clotting, immune response, and inflammatory processes. The AA fatty acid aids in the constriction of blood vessels and the formation of blood clots, and EPA aids in the relaxation of blood vessels and inhibits blood clotting. Although they have opposite functions, both are necessary to maintain a healthy balance between excessive bleeding and excessive blood clotting (Clandinin, 2000).

With changes in food production and diet, the consumption of omega-6 has risen in this country while omega-3 consumption has fallen. Ideally, intake of omega-6 fatty acids should be no more than 10 times that of omega-3 fatty acids (DRI, 2002), some believe it should be even lower at 4:1 (Simopoulos, 1999). Today in the typical U.S. diet, omega-6 intake is up to 20-30 times more than omega-3 intake (Simopoulos, 1999).

. . . . . .

About 80% of the fatty acid in beef is composed of palmitic (C16:0), stearic (C18:0), and oleic acid (C18:1). The remaining 20% is distributed among 30 different fatty acids. Inference of the health effect of fatty acids is based on experimental diets enriched with selected fatty acids. Oleic acid (C18:1) is the primary monounsaturated fatty acid in beef and accounts for about 33% of the fatty acid in beef. It is also found in rich amounts in olive, canola, and peanut oils. Available evidence indicates that while most saturated fatty acids raise serum cholesterol concentrations the monounsaturated oleic acid does not (Denke, 1994).