Omega-3, Omega-6, and DHA

When we have insufficient omega-3 fat, we do not produce enough DHA, a long-chain omega-3 fat with anti-inflammatory effects. High levels of arachidonic acid and low levels of omega-3 fats can be a contributory cause of heart disease, stroke, autoimmune diseases, skin diseases, depression, and possibly increased cancer incidence.1 Most Americans would improve their health if they consumed more omega-3 fats and less omega-6 fats. I recommend that both vegetarians and nonvegetarians make an effort to consume one to two grams of omega-3 fat daily.

A diet very high in omega-6 fat makes matters worse; your body makes even less DHA fat. We need enough DHA fat to ensure optimum health. The high level of omega-6 fat competes for the enzymes involved in fatty acid desaturation (conversion to longer-chain fats) and interferes with the conversion of alpha-linolenic acid (omega-3) to EPA and DHA. Therefore, our high fat intake contributes to our DHA fat deficiency.

Our modern diet, full of vegetable oils and animal products, is very high in omega-6 fat and very low in omega-3 fat; the higher the omega-6 to omega-3 ratio, the higher the risk of heart disease, diabetes, and inflammatory illnesses.2
1. Siguel, E. N., and R. H. Lerman. 1994. Altered fatty acid metabolism in patients with angiographically documented coronary artery disease. Metabolism 43: 982–83; Simon, J. A., J. Fong, J. T. Bernoert Jr., and W. S. Browner. 1995. Serum fatty acids and the risk of stroke. Stroke 26 (5): 778–82; Fatty acid reportedly lowers stroke risk. 1995. Medical Tribune, June 8, p. 20; Harbige, L. S. 1998. Dietary n-6 and n-3 fatty acids in immunity and autoimmune disease. Proc. Nutr. Soc. 67 (4): 555–62; Horrobin, D. F. 2000. Essential fatty acid metabolism and its modification in atopic eczema. Am. J. Clin. Nutr. 71 (1 supp.) 367s–72s; Adams, P. B., S. Lawson, A. Sanigorski, and A. J. Sinclair. 1996. Arachidonic acid to eicosapentaenoic acid ratio in blood correlates positively with clinical symptoms of depression. Lipids 31 Supp.: s157–61; Edwards, R., M. Peet, J. Shay, and D. Horribin. 1998. Omega-3 polyunsaturated fatty acid levels in the diet and in red blood cell membranes of depressed patients. J. Affect. Disord. 48 (2–3): 149–55; Rose, D. P. 1997. Effects of dietary fatty acids on breast and prostate cancers: evidence from in vitro experiments and animal studies. Am. J. Clin. Nutr. 66 (6 supp.): 1513s–22s.

2. Simopoulos, A. P. 1999. Essential fatty acids in health and chronic disease. Am. J. Clin. Nutr. 70 (3): 560–69.
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