Vitamin E requirement in relation to dietary fish oil and oxidative stress in elderly

A growing body of evidence shows that oxygen radicals and other products of free radical reactions are involved in aging and age-related degenerative diseases. Recent studies have suggested that fish oils (FO) have a potentially beneficial effect on age-associated diseases. Consumption of FO may increase requirement for vitamin E, especially under conditions where oxidative stress is increased. Vitamin E requirement increases with increased intake of dietary polyunsaturated fatty acids (PUFA). This relationship may be exaggerated in elderly subjects. Our studies, as well as those of others, have shown that plasma lipid peroxides are significantly higher in older subjects compared to young subjects. Thus, in conditions where the percentage of highly unsaturated fatty acid increases in the membrane, older subjects may be more susceptible to oxidative damage. In a series of human studies, we found that older women, receiving FO supplements for 3 months exhibited a greater increase in plasma PUFA compared to young subjects. By substituting membrane fatty acids with the potentially unstable (n-3) fatty acids of FO, older subjects were found to be at greater risk of oxidative stress than young subjects. In addition, when exposed to eccentric exercise-induced oxidative stress, older men, receiving vitamin E supplements for 48 days, exhibited significantly lower levels of lipid peroxides in urine compared to placebo control. These data indicate that older subjects are more susceptible to oxidative stress and may benefit from the antioxidant protection provided by vitamin E.