The unsaturated or essential fatty acids in our diet come primarily from liquid vegetable oils. Some of these contain vitamin E as well, which protects them from oxidation. There are two essential fatty acids which the body does not make and thus must be obtained from the diet (many sources state three, but arachidonic can be made from linoleic acid in humans). These are linoleic (L A) and linolenic (LNA) acids, found mainly in seeds, wheat germ, cod liver oil, and the golden vegetable oils, such as soy, safflower, and corn. Flaxseed (linseed) oil is probably our best oil, being particularly high in both omega-3 as alpha-linolenic acid and omega-6 fatty acids in the right balance for us. Evening primrose oil is high specifically in gamma-linolenic acid, an omega-6 fatty acid, and the fish oils are high in omega-3 fatty acids, particularly eicosapentaenoic acid (EPA).
The essential fatty acids (EFAs) are very important to the body for cell and organ respiration and to add resiliency and lubrication to the tissues. It is thought that the EFAs can increase the solubility of cholesterol deposited in the arterial walls and can support adrenal and thyroid gland activity. A relative increase in intake of the EFA oils (the polyunsaturates) in proportion to the saturated animal fats will help reduce blood cholesterol, an important factor in reducing the risk of cardiovascular disease. Linolenic acid is the most important EFA in humans. This omega-3 fatty acid is the precursor of the protective oils now known to be found in fish and flaxseed. Linolenic and the other omega-3 fatty acids are thought to be needed in a 2:1 ratio over the omega-6 fatty acids, including those derived from linoleic acid. Linolenic is also essential and is found in most vegetable oils, however, higher amounts of this fatty acid, which is the precursor of arachidonic acid, may be more inflammatory than linolenic acid. This is especially true when vitamins A and E are depleted.
Deficiency of the EFAs can reduce growth and skin, tissue, and joint lubrication. Low levels in the body have been seen in such conditions as prostate enlargement, psoriasis, anorexia nervosa, hyperactivity, and multiple sclerosis. Deficiency problems of EFAs may include acne, diarrhea, dry skin, eczema, alopecia (hair loss), gallstones, and slow growth and wound healing.
Vitamin F has been used in the treatment of eczema, psoriasis, skin allergies, prostatitis, and asthma. It is required in amounts equaling in at least 2 percent of caloric intake, 1–2 teaspoons a day depending on weight.