If you are like the typical American, you are probably suffering from "fat-phobia." The mass media has led us to believe that all dietary fat is evil and that by avoiding it like the plague, we can reduce body fat and prevent killer diseases. The truth of the matter is actually somewhat involved but it demands understanding if optimal health is to be achieved. 

Fats have many essential roles in the body. They regulate temperature, cushion organs, aid vitamin absorption, help conduct nerve impulses, serve as precursors to hormone-like compounds, and as components of cell membranes, they play a role in intercellular communication. The physical and chemical properties, and therefore the physiologic effect in the body, of any given fat are a function of the types of fatty acids it contains. Fatty acids can be classified as saturated, monounsaturated or polyunsaturated. 

SATURATED FATS

Compared with the other two groups of fats, saturated fats are more solid and "sticky" in the body. In excess amounts, they produce stiffening and consequent impaired functioning of cell membranes. They cause platelets to become sticky and blood cholesterol levels to increase, both of which contribute to cardiovascular disease. Saturated fats are also associated with obesity, some cancers, and diabetes. Foods high in saturated fat are beef, eggs, pork, lamb, and dairy products. Importantly, these foods also account for 90 percent of the pesticide residues found in the average diet. Therefore, eating "organic" versions of these same foods may minimize some of the negative health effects. 

Although tropical oils are highly saturated and have a bad reputation, there is no harm in eating them occasionally, provided they are fresh. The only concern here is that the palmitoleic acid they contain can interfere with essential fatty acid metabolism. Palmitoleic acid is also found in milk. So go ahead and enjoy an occasional raw coconut. 

MONOUNSATURATED FATS

Oleic acid is the most important monounsaturated fatty acid to human health. It is found in large quantities in olives, avocados, almonds, pistachios, peanuts, pecans, cashews, filberts, and macadamia nuts. Several studies have shown that when substituted for complex carbohydrates, a high monounsaturated fat diet produces more healthful effects in diabetics. In moderation, it is beneficial for the cardiovascular system. Olive oil contains powerful antioxidants. In excess, monounsaturated fatty acids can interfere with essential fatty acid metabolism. 

POLYUNSATURATED FATS

There are only two fatty acids that the body normally cannot produce from other compounds. For this reason, they are referred to as "essential." They are linoleic acid and alpha-linolenic acid. These polyunsaturated fatty acids are associated with a great number of beneficial effects in the body, a few of which are: they optimize cellular function by increasing cell membrane fluidity; they lower blood cholesterol and triglyceride levels; they increase stamina and reduce recovery time from exercise; they reduce inflammation and speed healing; they reduce platelet stickiness and enhance immune function; they increase burning of body fat for energy; and they are essential to brain and eye development through early childhood. Unfortunately, alpha-linolenic acid insufficiency is particularly common. Linoleic acid is found in safflower, sunflower seeds, hemp seeds, soybeans, walnuts, pumpkin seeds, sesame seeds and flax seeds. Alpha-linolenic acid is found in greatest concentrations in hemp seeds, canola, soybeans, walnuts, pumpkin seeds, dark green leaves, and especially flax seeds. 

One of the functions of the essential fatty acids is their conversion in the body to eicosanoids. Eicosanoids are hormone-like compounds that have varied and powerful effects on virtually every body tissue. These conversions require several biochemical steps. With age, certain nutrient insufficiencies, other dietary excesses, and sometimes genetic determination, these conversions do not take place to an adequate degree. The solution to this problem is to consume the intermediate compounds that are more direct precursors to the eicosanoids. These are gamma-linolenic acids, which are found in evening primrose oil, black currant seed oil, borage oil, and eicosapentaenoic acid (EPA), which is found in cold water fish such as trout, salmon, sardines and mackerel. 

Another important polyunsaturated fatty acid is arachidonic acid. It is found in relatively high concentrations in beef, pork, lamb, dairy, and shellfish. This fatty acid gets converted to eicosanoids with very different effects from those derived from the essential fatty acids. Arachidonic acid results in inflammation, platelet aggregation, salt and water retention, and cell transformation. You may have noticed that arachidonic acid is found in the same animal foods that are high in saturated fats. The arachidonic acid is probably more responsible for the negative health effects linked with these foods than the saturated fats. 

Arachidonic acid can also be produced in the body. Insufficient levels of EPA, excess levels of trans fatty acids and of insulin all result in greater production of arachidonic acid. Interestingly, insulin levels are stimulated by a relative excess of dietary carbohydrates, especially sugars.