Health Effects of Omega-3 Polyunsaturated Fatty Acids


Greek-American Review

There are two families of essential fatty acids, the omega 6 and omega 3 polyunsaturated fatty acids (PUFA). They are essential because human beings cannot make them and they must be obtained from the diet.

On the basis of estimates from studies in Paleolithic nutrition and modern day hunter gatherer populations, it appears that human beings evolved consuming a diet that was much lower in saturated fatty acids than is today's diet. Further-more, the diet contained small and roughly equal amounts of omega 6 and omega 3 PUFA (ratio of 1 2: 1) and much lower amounts of trans fatty acids than does today's diet.

The current Western diet is very high in omega6 fatty acids (the ratio of omega 6 to omega 3 fatty acids ranges between 10 30: 1) because of the recommendation to substitute vegetable oils, corn oil. sunflower, safflower, cotton-seed and soybean oil that are high in omega 6 fatty acids for saturated fats to lower serum cholesterol concentrations. Furthermore' intake of omega 3 fatty acids is much lower today because of the decrease in fish consumption, and the industrial production of animal feeds rich in grains containing omega 6 fatty acids, leading to production of meat rich in omega 6 and poor in omega 3 fatty acids. The same is true for poultry, eggs and farmed fish. Even cultivated vegetables contain fewer omega 3 fatty acids than do plants in the wild. In summary, modern agriculture, with its emphasis on production, has decreased the omega 3 fatty acid content in many foods: green leafy vegetables, animal meats, eggs, and even fish, while it has increased the amount of omega6 fatty acids in foods, leading to high omega 6 intake for the first time in the history of human beings in many countries around the world. The traditional diet of Crete (Greece) is consistent with the Paleolithic diet relative to the omega 6: omega 3 ratio. The Lyon Heart Study, which was based on a modified diet of Crete, had an omega 6:omega 3 ratio of 4: 1 resulting in a 70% decrease in risk for cardiac death. The higher the ratio of omega 6 to omega 3 fatty acids in platelet phospholipids, the higher is the death rate from cardiovascular disease. As the ratio of omega 6 PUFA to omega 3 PUFA increases, the prevalence of t % p,- diabetes also increases. A balance between the omega 6 and omega 3 fatty acids is a more physiologic state in terms of gene expression, eicosanoid metabolism and cytokine production.

Today, more is known about the mechanisms and functions of omega 3 fatty acids than other fatty acids. Research has shown that docosahexaneoic acid (DHA) an omega 3 fatty acid found in fish oil is essential for the development of the premature infant relative to visual acuity, visual function and maturation. In the full term infant DHA may influence visual acuity and neural pathways associated with the developmental progression of language acquisition. These findings have led to inclusion of DHA and arachidonic acid (AA), an omega 6 fatty acid, in infant formula by most countries around the world.

When humans ingest fish or fish oil, the ingested EPA and DHA partially replace the omega 6 fatty acids [especially AA] in cell membranes, particularly those of platelets, erythrocytes, neutrophils, monocytes and liver cells. Recent research suggests that the response to omega 3 fatty acids may be geno-type dependent since certain individuals respond more than others. It is essential to take genetic variation into consideration in setting up clinical intervention trials. There is a need to move away from the long term prospective studies, and proceed with genotype specific clinical intervention trials.

Artemis P Simopoulos, MD. is the President of The Center for Genetics, Nutrition and Health in Washington. D. C. and author of The Omega Diet (Harper Collins, 1999)

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