By Mary Enig, PhD, and Sally Fallon
Classification Of Fatty Acids By Length
Researchers classify fatty acids not only according to their degree of saturation but also by their length.
Short-chain fatty acids have four to six carbon atoms. These fats are always saturated. Four-carbon butyric acid is found mostly in butterfat from cows, and six-carbon capric acid is found mostly in butterfat from goats. These fatty acids have antimicrobial properties-that is, they protect us from viruses, yeasts and pathogenic bacteria in the gut. They do not need to be acted on by the bile salts but are directly absorbed for quick energy. For this reason, they are less likely to cause weight gain than olive oil or commercial vegetable oils.27 Short-chain fatty acids also contribute to the health of the immune system.28
Medium-chain fatty acids have eight to twelve carbon atoms and are found mostly in butterfat and the tropical oils. Like the short-chain fatty acids, these fats have antimicrobial properties; are absorbed directly for quick energy; and contribute to the health of the immune system.
Long-chain fatty acids have from 14 to 18 carbon atoms and can be either saturated, monounsaturated or polyunsaturated. Stearic acid is an 18-carbon saturated fatty acid found chiefly in beef and mutton tallows. Oleic acid is an 18-carbon monounsaturated fat which is the chief component of olive oil.
Another monounsaturated fatty acid is the 16-carbon palmitoleic acid which has strong antimicrobial properties. It is found almost exclusively in animal fats. The two essential fatty acids are also long chain, each 18 carbons in length. Another important long-chain fatty acid is gamma-linolenic acid (GLA) which has 18 carbons and three double bonds. It is found in evening primrose, borage and black currant oils. Your body makes GLA out of omega-6 linoleic acid and uses it in the production of substances called prostaglandins, localized tissue hormones that regulate many processes at the cellular level.
Very-long-chain fatty acids have 20 to 24 carbon atoms. They tend to be highly unsaturated, with four, five or six double bonds. Some people can make these fatty acids from EFA's, but others, particularly those whose ancestors ate a lot of fish, lack enzymes to produce them. These "obligate carnivores" must obtain them from animal foods such as organ meats, egg yolks, butter and fish oils.
The most important very-long-chain fatty acids are dihomo-gamma-linolenic acid (DGLA) with 20 carbons and three double bonds; arachidonic acid (AA) with 20 carbons and four double bonds; eicosapentaenoic acid (EPA) with 20 carbons and five double bonds; and docosahexaenoic acid (DHA) with 22 carbons and six double bonds. All of these except DHA are used in the production of prostaglandins, localized tissue hormones that direct many processes in the cells. In addition, AA and DHA play important roles in the function of the nervous system.29
The Dangers Of Polyunsaturates
The public has been fed a great deal of misinformation about the relative virtues of saturated fats versus polyunsaturated oils. Politically correct dietary gurus tell us that the polyunsaturated oils are good for us and that the saturated fats cause cancer and heart disease. The result is that fundamental changes have occurred in the Western diet.
At the turn of the century, most of the fatty acids in the diet were either saturated or monounsaturated, primarily from butter, lard, tallows, coconut oil and small amounts of olive oil. Today most of the fats in the diet are polyunsaturated from vegetable oils derived mostly from soy, as well as from corn, safflower and canola.
Modern diets can contain as much as 30% of calories as polyunsaturated oils, but scientific research indicates that this amount is far too high. The best evidence indicates that our intake of polyunsaturates should not be much greater than 4% of the caloric total, in approximate proportions of 2 % omega-3 linolenic acid and 2 % omega-6 linoleic acid.30
EFA consumption in this range is found in native populations in temperate and tr