Heli J. Roy | 7/2/2005 1:12:46 AM
Omega-3 and omega-6 fatty acids are both essential for human health. Americans, however, consume far too many omega-6 fats and not enough omega-3 fats, according to LSU AgCenter nutritionist Dr. Heli Roy.
In typical Western diets, the ratio of omega-6 to omega-3 essential fatty acids is about 15 to 1.
Sources of omega-6 polyunsaturated fatty acids are liquid vegetable oils, including soybean oil, corn oil and safflower oil.
Plant sources of omega-3 polyunsaturated fatty acids include soybean oil, canola oil, walnuts, and flaxseed.
Long-chain omega-3 fatty acids come from fish and shellfish. Fish that naturally contain more oil, such as salmon, trout and herring, are higher in omega-3 fatty acids than are lean fish like cod, haddock and catfish.
Research has shown that long-chain unsaturated omega-3 fatty help reduce the risk of cancer. Animal studies reveal that high intake of long-chain unsaturated omega-3 fatty acids can slow the growth of cancer cells, and they also can reduce the side effects of chemotherapy agents.
Dr. Elaine Hardman of the Pennington Biomedical Research Center studied the effect of omega-3 fatty acids in reducing tumor growth in mice that were treated with ionizing radiation. The mice were given diets of varying omega-6 and omega-3 fatty acid levels, and they were treated by ionizing radiation to see whether the type of fatty acid in the diet would reduce the incidence of cancer.
The four groups of mice were: (1) corn oil diet (high in omega-6 fatty acids), no Ionizing Radiation (IR) treatment; (2) corn oil diet with IR treatment; (3) omega-3 enriched diet, no IR treatment; and (4) omega-3 enriched diet with IR treatment.
Tumor growth rate was the fastest in mice that received the corn oil diet (omega-6 fatty acid). Mice that received omega-3 fatty acid suppressed tumor growth as effectively as those that received omega-6 fatty acid and ionizing radiation.
Omega-3 fatty acid alone suppressed tumor growth as well as the ionizing radiation. Those mice that received omega-3 fatty acid and ionizing radiation were not more successful in repressing tumor growth than those that received either treatment alone. The ratio of omega-3 to omega-6 was about 3 to 1 in this study.
The Dietary Guidelines for Americans 2005 recommend that we consume less than 10 percent of calories from saturated fatty acids and less than 300 mg/day of cholesterol. Keep trans fatty acid consumption as low as possible.
Roy says most dietary fats should come from sources of polyunsaturated and monounsaturated fatty acids. The nutritionist recommend keeping total fat intake between 20 percent to 35 percent of calories, with most fats coming from sources of polyunsaturated and monounsaturated fatty acids, such as fish, nuts and vegetable oils.
For information on related nutrition, family and consumer topics, click on the Family and Home link at the LSU AgCenter Web site at www.lsuagcenter.com. For local information and educational programs, contact an extension agent in your parish LSU AgCenter office.