Essential Fatty Acids
Another factor must be kept in mind when deciding which fats to eat. There are two polyunsaturated fatty acids that are "essential fatty acids." Just like the essential amino acids, these essential fatty acids must be obtained from the diet. The essential fatty acids are linoleic (lyn-o-lay-ic) acid and linolenic (lyn-o-len-ic) acid. Essential fatty acids have many functions in the body. They are needed to convert the energy in food to ATP; to transfer oxygen from the air to red blood cells and from the red blood cells to tissues; to facilitate communication from one cell to the next; to produce and release enzymes and hormones; to make substances that regulate blood pressure, inflammation, immune response and blood clotting, all of which are important in healing injured and damaged tissues.

Linoleic acid is found in significant amounts in all polyunsaturated fats (i.e., soy oil, sunflower oil, safflower oil) and in small to moderate amounts in all monounsaturated fats (i.e., olive oil and sesame oil). Therefore, linoleic acid is found in sufficient quantities in most diets. Linolenic acid, on the other hand, is found abundantly only in flax seed oil. It is found in moderate amounts in hemp seed oil and small amounts in soy oil, wheat germ oil, walnut oil and seaweed. However, the most important function of linolenic acid is its conversion to two other fatty acids--EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). These fatty acids are found in significant amounts in fish oil from cold-water fish, such as salmon, herring, sardines and mackerel. If you eat cold-water fish twice a week and get plenty of whole foods, you should get adequate amounts of both essential fatty acids.

Sterols And Cholesterol
Dietary fats also supply sterols, the third lipid. The primary sterol in the diet is cholesterol, and it is only found in animal fats. Cholesterol has been given so much bad press that its necessary and vital functions are frequently overlooked.

Along with the phospholipids, cholesterol is an important component of the cell membrane. Cholesterol helps regulate the exchange of nutrients and waste products between the inside and the outside of the cell. This movement is called membrane transport. Cholesterol controls the fluidity of the cell membrane. Cell membranes that are either too flexible or too rigid will have reduced membrane transport resulting in poor cell function. When the diet contains an abundance of polyunsaturated fatty acids (those oils that easily become rancid), the phospholipids in the cell membrane will be primarily polyunsaturated fatty acids. Polyunsaturated fatty acids make the cell membranes very fluid or flexible. When this happens, greater quantities of cholesterol will move into the cell membrane to reduce its flexibility. On the other hand, if the diet contains primarily saturated fats, the cell membranes will become too rigid. Cholesterol will then leave the cell membrane to cause an increase in the cell membrane flexibility.

Another important function of cholesterol is as a structural component of cell wall receptor sites. Receptor sites are locations where neurotransmitters and hormones can attach to the cell membrane and transmit a message to the cell. Receptor sites are similar to a docking port on a space station. Only a spacecraft with the appropriate structural configuration can attach to the docking port. And if the docking port were constructed without all the necessary parts, the spacecraft would not be able to dock and unload its cargo. On cells, only compounds with the correct shape can fit into the receptor site and transmit their message to the cell. For example, serotonin is a neurotransmitter that carries a message from one nerve cell to the next. One of its functions is to impart a feeling of well-being. The drug Prozac, which increases serotonin levels, is a well-known antidepressant. Many studies have shown that low cholesterol level is associated with increased rates of depression and suicide. This may, in part, be because without sufficient dietary cholesterol, the receptor site is not formed correctly, and serotonin cannot efficiently attach and send its message to the cell.

Cholesterol is also an important component of bile. Bile breaks down large fat particles so the fat-digesting enzyme, lipase, can further digest the fat into individual fatty acids. Bile is also necessary for the absorption of fat-soluble vitamins.

Vitamin D is actually made by the body from cholesterol. Insufficient dietary cholesterol can contribute to a vitamin D deficiency. Cholesterol is also the precursor to the adrenal and sex hormones. Without adequate cholesterol, these hormones may not be produced in sufficient quantities for optimal health.

Many tissues in the body, especially the liver, can manufacture cholesterol. The manufacturing of cholesterol, however, requires the use of significant energy. It is much more efficient for the body to obtain cholesterol from the diet than to have to manufacture it from other compounds within the body. When functioning properly, the liver is so efficient at monitoring and manufacturing cholesterol that a low-cholesterol diet results in only a 10 percent drop in the blood cholesterol level.

Now that you have a much better understanding of cholesterol, dietary fats and the fatty acids they contain, we can discuss why some fats are considered "good" and other fats are considered "bad." In reality, in moderation, no fats are completely good or bad for everyone. However, individuals with certain genetic risk factors, such as heart disease, usually benefit from a diet low in saturated fats, such as butter. Most saturated fats stimulate the production of LDL cholesterol, or "bad" cholesterol. LDL cholesterol is considered "bad" because high LDL cholesterol has been linked to an increased risk for heart disease. A diet high in polyunsaturated fat, such as corn oil, tends to lower LDL cholesterol. Unfortunately, this diet also lowers HDL cholesterol, the "good cholesterol," which has shown a protective effect against heart disease. Monounsaturated fats such as olive oil, on the other hand, tend to lower LDL cholesterol and maintain, or even increase, the HDL cholesterol. Therefore, an individual with heart disease in his or her family history, and/or a high LDL and low HDL, will usually benefit from a diet containing mostly monounsaturated fats. On the other hand, someone with low total cholesterol, low LDL cholesterol and no history or risk of heart disease will benefit from eating saturated fats, such as the fats found in dairy products. As you can see, it is necessary to look at many factors to determine the amount and type of dietary fat that is right for each individual.

A discussion of fats would not be complete without a brief discussion of hydrogenated oils. Hydrogenated oils are man-made saturated fats. The hydrogenation process takes cheap polyunsaturated liquid oils, which are unstable, and converts them to solid stable fats. Hydrogenated oils are used to extend the shelf life of many processed foods, especially baked goods, such as cakes, cookies and crackers. Due to processing requirements, hydrogenated oils contain fatty acid fragments not found in nature, as well as trace amounts of heavy metals, including aluminum. Frequently, the hydrogenation process is deliberately arrested when the oil is only partially hydrogenated. This incomplete hydrogenation results in the formation of large amounts of trans-fatty acids.

Trans-fatty acids have a very different structure than the majority of natural fatty acids. This change in structure gives the hydrogenated oil its solid consistency and stability. If foods containing partially hydrogenated oils are eaten frequently, the body will have to use these "unnatural" fatty acids to make and repair cell membranes. This makes the cell membrane more rigid, and the utilization of essential fatty acids is blocked. Studies have shown that regular intake of partially hydrogenated oils in crackers, cookies, snack chips and other foods causes a reduction in HDL cholesterol, the "good" cholesterol, and increased hardening of the arteries and cardiovascular disease. Trans-fatty acids and hydrogenated oils should be avoided as much as possible.

Though it has not been proven with double-blind studies, several leading scientists suspect that many of today's common health problems can be linked to the intake of trans-fatty acids and associated compounds. Herbert Dutton, a leading lipid chemist, states, "If the hydrogenation process were discovered today, it probably could not be adopted by the oil industry."

He adds, "The basis for such comment lies in the recent awareness of our prior ignorance concerning the complexity of compounds formed during hydrogenation and their metabolic and physiological fate."¹

Basically, he is saying there is too little we do know and too much we do not know about the ingestion of hydrogenated and partially hydrogenated oils.

The first generations of children raised on foods with high levels of hydrogenated oils, such as margarine, are now adults. They have been a living experiment, and all the results of this experiment have yet to be identified. During the past decade, the media has sporadically highlighted the few known detrimental effects of trans-fatty acids. It is therefore astonishing to see the wide variety of foods in the grocery store that still contain partially hydrogenated oils. This means the average American is still consuming significant quantities of these unnatural fats.

The average "health conscious" individual, on the other hand, is well aware of the health risks associated with trans-fats and with ingestion of excess fats in general. Unfortunately, the American mentality seems to be if a little is good, a lot must be better. Or in the case of fat, if a lot is bad, then none is better. Therefore, people aware of the health risks associated with fat deliberately eliminate almost all fat from their diets. These individuals do not obtain the quantities of fat and essential fatty acids necessary to maintain optimal health.

Another group with inadequate quantities of dietary fat are perpetual dieters. They eliminate fats to reduce their intake of calories. Even if they do lose weight, in the long term they develop health problems associated with inadequate intake of essential fatty acids. The cause of these health problems may be incorrectly identified because most physicians and many dietitians are taught the problems of excess dietary fat, but know very little about deficiency of essential fatty acid. From this discussion of fats and lipids, you should now realize that a moderate intake of quality fat, with a balance of saturated, monounsaturated and polyunsaturated fats, is needed to maintain optimal health.

In the next article, we will discuss how to balance our intake of carbohydrates, proteins and fats.

•••

Ben E. Benjamin, Ph.D. in sports medicine and education, is the founder and president of the Muscular Therapy Institute in Cambridge, Massachusetts.

Joy Bicknell, MS, CNS, has been working in alternative health care for more than 15 years. She has a Master of Science in Human Nutrition, and is a Certified Nutritional Specialist. She may be contacted at: joynutrition@mediaone.net.

If you wish to purchase a bound copy of the entire article series, E-mail Ben@mtti.com, or write to Benjamin at: 175 Richdale Ave., #106, Cambridge, MA 02140.

References

1. Quote originally published by Brisson, G.J. Lipids In Human Nutrition. New Jersey: Burgess, 1981. Quote taken from Udo Erasmus. Fats That Heal, Fats That Kill. Burnaby, British Columbia: Alive Books, 1993.