BELTSVILLE, MARYLAND. Fish oils are beneficial in the prevention of cancer and cardiovascular disease. They do, however, oxidize very easily and therefore add to the oxidant stress on the body. An experiment was recently carried out by the U.S. Department of Agriculture to see if an increased intake of vitamin E could counteract this detrimental effect of fish oils. Forty men aged 32 to 44 were involved. The men consumed a controlled diet for a total of 28 weeks. For the first 10 weeks they received placebo oil capsules (15 g/day), for the next 10 weeks they received fish oil capsules (15 g/day), and for the last 8 weeks they received the fish oil and vitamin E (200 mg) (all-rac-alpha-tocopherol). The urinary excretion of peroxidation products (malondialdehyde) more than doubled when the fish oil capsules were introduced but then dropped by a factor of four when vitamin E was added (taking fish oil and vitamin E together). The vitamin E concentration in the red blood cells dropped very significantly when fish oil was ingested but more than recovered with the vitamin E supplement. It is concluded that the negative effects of fish oil consumption can be overcome by taking the fish oil and vitamin E together.
LONDON, ENGLAND. A recent experiment carried out at King's College in London showed that daily intake of a fish oil supplement reduces the plasma concentration of vitamin E to below normal range. Nine healthy male subjects were given a daily fish oil supplement containing 2.1 g docosahexaenoic acid (DHA) and 0.8 g eicosapentaenoic acid (EPA) for a six week period. The proportion of DHA and EPA in the blood increased during the trial while the concentration of very-low-density-lipoprotein-cholesterol and triacylglycerol decreased. Blood pressure fell slightly during treatment, but rose again once the fish oil supplementation was discontinued. Of particular interest was the finding that alpha-tocopherol (vitamin E) concentration in the blood fell from 20 micromol/l to about 10 micromol/l during the experiment. This raises the question whether fish oil supplementation increases the need for antioxidant supplementation and whether fish oil and vitamin E should be taken together.
CORVALLIS, OREGON. There is ample evidence that fish consumption and fish oil supplementation help protect against heart disease. However, the main components of fish oils, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are highly unsaturated and would therefore be prone to oxidation. This has prompted some researchers to express concern that fish oils might contribute to the lipid peroxidation involved in the development of atherosclerosis.