The Good, The Bad and The Ugly

Fat is a headline-maker. Newspapers, magazines and the evening news regularly attack fat as a contributor to obesity, heart disease and dozens of other modern diseases. But only part of the story is being told in these reports. Not all fats are bad. In fact, the essential fatty acids (EFA), as their name implies, are absolutely essential for good health.

The Facts on Fats

Fats are one of the three categories of dietary macro-nutrients; the others being carbohydrates and protein. The category of fats is further divided into the classes of saturated, monounsaturated and polyunsaturated.

The first category of fats, saturated fatty acids, are solid at room temperature and found in such foods as butter, margarine, beef, chicken and coconut oil. Saturated fats are responsible for most of the bad press about fats. As a result the U.S. government, doctors and nutritionists recommend that Americans limit their intake of "bad" saturated fats.

The second category of fats, monounsaturated fatty acids, are liquid at room temperature. Monounsaturated fats, such as olive and canola oils, form the basis of the healthful Mediterranean diet. Monounsaturated oils are less likely to oxidize than polyunsaturated fats when used for stir-frying and other cooking.

Polyunsaturated fatty acids are the third category . Examples of polyunsaturated fats are flax oil, safflower oil, walnut oil and most other vegetable oils. Like monounsaturated fats, these oils are liquid at room temperature. However, polyunsaturated fats break down at high temperatures and should not be used for high-temperature cooking.

The essential fatty acids are found in polyunsaturated fats. The two types of essential fatty acids are:

• Omega-3 fatty acids (alpha-linolenic acid)

• Omega-6 fatty acids (linoleic acid)

Trans-fatty Acids: The Ugly Fats

Trans-fatty acids are created from polyunsaturated fats during exposure to heat or in a process called hydrogenation. Margarine and other processed fats have undergone hydrogenation to become trans-fatty acids. As a result, these fats are closer in composition to saturated fats.*1

The long-term effects of trans-fatty acids in the diet are not known, but some harmful effects have been found.*1,2,3 Women who consume the most trans-fatty acids have a 50 percent increased risk of heart disease.*2 One study concluded that trans-fatty acids are as bad as saturated fat since trans-fatty acids reduce levels of the “good” cholesterol  while raising those of the “bad” cholesterol.*1

Why Do We Need Essential Fatty Acids

Essential fatty acids contribute to the maintenance of a healthy body in several ways. For example, they are an important component of cell membranes, help insulate the nerves, cushion and protect the tissues, help produce hormone-like substances called prostaglandins, and contribute to healthy skin and hair.*

Nuts, seeds and most vegetable oils are rich sources of the omega-6 fatty acids. An important type of omega-6 fatty acid, gamma-linolenic acid (GLA), is found in black currant seed, borage and evening primrose oils.

Fish is an abundant source for omega-3 fatty acids. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are two types of fatty acids in fish oil; while some vegetable sources, such as flax oil, contain alpha-linolenic acid. Apparently, the fatty acids in vegetables can be converted to EPA and DHA, since these substances are found in the blood of strict vegetarians.*4 Omega-3 fatty acids are destroyed in the manufacture of partially hydrogenated vegetable oils.

Benefits of Omega 3 Fatty Acids

Strengthening the cardiovascular system may be the most important benefit of omega-3 fatty acids.* Fish oil helps regulate cholesterol and triglyceride levels in the blood.*5 Years ago, scientists were impressed by the healthy cardiovascular systems of Greenland Eskimos, such as their low triglycerides, moderate cholesterol levels and “thinner” blood, which was slower to clot. When researchers examined their diets, they discovered the unusual fatty acids EPA and DHA derived from a diet based on fish, seal and walrus.6, 7

Europeans with greater amounts of omega-3 fatty acids in their diets are also more likely to have healthy hearts.*8 Adding fish oil, EPA or DHA to the diets of Europeans or Americans has been shown to produce the same desirable blood “thinning” effect seen in Eskimos.*9

Surprisingly, a few studies have not found a significant heart-protective effect from eating fish.10 11 However, these few negative trials do find that people who eat some fish have a trend toward healthier cardiovascular systems.*10

Omega-3 fatty acids lessen the amount of pro-inflammatory prostaglandins made in the body,12 which  lessens the painful inflammatory response.*13 Both DHA and EPA reduce levels of a specific prostaglandin, called prostaglandin-E2, which would otherwise interfere with proper immune function.*14

In addition, omega-3 fatty acids help maintain soft, smooth skin. Diets deficient in this essential fatty acid result in unhealthy, scaly skin. Adding omega-3 fatty acids back into the diet provides relief from this troubling skin condition.*15

Benefits of Omega 6 Fatty Acids

Omega-6 fatty acids are the most common type of fat in the average diet. The omega-6 fatty acids, linoleic, arachidonic, and gamma-linolenic (GLA) fatty acids, act as precursors to the majority of prostaglandins. Omega-6 fatty acids are key structural components of cell membranes, and are an integral part of the myelin sheath, which protects nerves.16

According to several double-blind research studies, GLA-rich black currant seed, evening primrose seed and borage oils help reduce swelling and inflammatory response in joints*4, 17, 18, 19a by significantly reducing the body’s production of pro-inflammatory prostaglandins and leukotrienes.*17 The GLA dosages used in research studies varied from 480 mg to 1,500 mg per day.

Gamma-linolenic acid may help reduce elevated levels of cholesterol and triglycerides when supplements of 3,000 mg of GLA-rich oil are taken daily.*20 GLA has also been shown to significantly decrease blood-clotting.*20

Ideal Intake of Essential Fatty Acids

Eskimos on a traditional diet consume approximately 5 grams of omega-3 fatty acids daily, which is equivalent to about a pound of salmon. Yet, men including as little as one-half pound of fatty fish in their diet every week were found to have healthier cardiovascular systems compared to non-fish eaters.*21 Researchers from Sweden report that fish has a “dose-dependent” effect; that is, the more fish in your diet, the healthier your heart.*22 While optimal intake of omega-3 fatty acids remains unknown, some researchers recommend a daily intake of 3,000 mg. *23, 24

To prevent a deficiency in adults, about two percent of daily calories should be derived from omega-6 fatty acids. This is equivalent to approximately 4.5 grams of omega-6 fatty acids. Since vegetable oils contain an average of 60 percent omega-6 fatty acids, about 2 teaspoons of oil should be adequate to prevent deficiencies. Nutritionists do not know the optimal intake of omega-6 fatty acids, however, most Americans are believed to consume adequate amounts.*

References

1. Mensink RP et al. Effect of dietary trans fatty acids on high-density and low-density lipoprotein cholesterol levels in healthy subjects. N Engl J Med, 1990; 323:439-45.

2. Willet WC et al, Intake of trans fatty acids and risk of coronary heart disease among women. Lancet, 1993; 341:581-5.

3. Troisi R. et al, Trans-fatty acid intake in relation to serum lipid concentration in adult men, Am J Clin Nutr, 1992; 56:1019-24.

4. Rothman D, DeLuca P, Zurier RB, Botanical lipids: effects of inflammation, immune responses, and rheumatoid arthritis. Semin Arthritis Rheum 1995;25(2):87-96.

5. Innis SM. n-3 fatty acid requirements of the newborn, Lipids, 1992; 27:879-85.

6. Dyerberg J, Bang HO. Haemostatic function and platelet polyunsaturated fatty acids in Eskimos. Lancet 1989;i:433-5.

7. Seidelin KN et al. n-3 fatty acids in adipose tissue and coronary artery disease are inversely related. Am J Clin Nutr 1992;55:1117-9.

8. Leaf A, Weber PC. Cardiovascular effects of n-3 fatty acids. N Engl J Med 1988;318:549-57 [review]

9. Morris MC et al. Fish consumption and cardiovascular disease in the Physicians’ Health Study: a prospective study. Am J Epidemiol 1995;142:166-75.

10. Ascherio A et al. Dietary intake of marine n-3 fatty acids, fish intake, and the risk of coronary disease among men. N Engl J Med 1995;332:977-82.

11. Salonen JT et al. Intake of mercury from fish, lipid peroxidation, and the risk of myocardial infarction and coronary, cardiovascular, and any death in Eastern Finnish Men. Circulation 1995; 91:645-55.

12. Sanders TAB Roshani F. The influence of different types of n-3 polyunsaturated fatty acids on blood lipids and platelet function in healthy volunteers, Clin Sci 1983; 64:91-9.

13. DeLuca P, Rothman D, and Zurier RB: Marine and botanical lipids as immunomodulatory and therapeutic agents in the treatment of rheumatoid arthritis. Rheum Dis Clin North Am 1995;21(3):759-775.

14. Dyerberg J et al. Eicosapentaenoic acid and prevention of thrombosis and atherosclerosis? Lancet 1978;ii:117-9.

15. Ongoing research by Dr. M.J. James, Rheumatology Unit at Royal Adelaide Hospital in Australia.

16. Dupont J. Lipids. In Present Knowledge in Nutrition, ILSI, 1990, pp 63.

17. Leventhal LJ, Boyce EG, Zurier RB, Treatment of rheumatoid arthritis with gamma linolenic acid. Ann Intern Med 1993;119(9):867-73.

18. Pullman-Mooar S, Laposata M, Lem D, Holman RT, Leventhal LJ, DeMarco D, Zurier RB, Alteration of the cellular fatty acid profile and  the production of eicosanoids in human monocytes by gamma-linolenic acid. Arthritis Rheum 1990;33(10):1526-33.

19. Levanthal LJ, Boyce EG, Zurier RB. treatment of rheumatoid arthritis with black currant seed oil. Br J Rheumatol 1994;33(9):847-52.

20. Guivernau M, Meza N, Barja P, Roman O, Clinical and experimental study on the long term effect of gamma-linolenic acid on plasma lipids, platelet aggregation, thromboxane formation and prostacyclin production. Prostaglandins Leukot Essent Fatty Acids 1994;51(5):311

21. Kromhout, D., et al. The inverse relation between fish consumption and 20-year mortality from coronary heart disease. N Engl J Med, 1985; 312(19):1205.

22. Norell, S.E., et al. Fish consumption and mortality from coronary heart disease. BMJ 1986;293:426.

23. Appel, L.J., et al. Does supplementation of diet with ‘fish oil’ reduce blood pressure? A meta-analysis of controlled clinical trials. Arch Intern Med 1993;153:1429-38.

24.  Geusens, P., et al. Longer-term effect of omega-3 fatty acid supplementation in active rheumatoid arthritis: a 12-month, double-blind, controlled  study. Arthrit Rheum 1994;37:824-9.