Antioxidant supplement and oxidant damage in healthy men - Dietary Intake

Nutrition Research Newsletter, April, 2003

Epidemiological studies show that increased consumption of fruits and vegetables is associated with a decreased risk of chronic degenerative diseases including cardiovascular disease and cancer. Antioxidants in fruits and vegetables may decrease risk of disease by modulating DNA damage, lipoprotein oxidation, platelet aggregation, leukocyte adhesion, and vascular function. Although many antioxidant supplementation studies have been conducted, the effect of antioxidant nutriture on disease risk remains uncertain. Reported antioxidant supplementation studies often involve healthy well-nourished individuals who already maintain a high antioxidant status before intervention, and who frequently are supplemented with pharmacological rather than nutritional amounts of the antioxidant vitamins. It has been suggested that studies of antioxidants and disease risk should include more subjects with a low intake or poor status of antioxidant nutrients, to increase the likelihood of detecting an impact of the intervention.

This recently published study is an antioxidant intervention study that included subjects that were primarily low fruit/vegetable eaters, and provided them with a modest antioxidant supplement that would approximate the antioxidant intake of high fruit/vegetable eaters with respect to vitamins C and E. Smokers were included in the study population because they are likely to have more oxidant stress, a lower antioxidant vitamin intake, and thus may show a greater benefit from an antioxidant intervention. Antioxidants were provided in the form of supplements instead of fruits and vegetables to eliminate other constituents in fruits and vegetables that could confound the study results.

Because oxidative damage has been strongly linked to chronic disease, the researchers measured biomarkers of in vivo oxidative damage to lipids and protein, before and after 90 days of antioxidant supplementation. The objective of the study was to determine whether a moderate supplement of antioxidant vitamins given to 77 healthy men eating less than the recommended 5 to 9 daily servings of fruits and vegetables would alter biomarkers of oxidant damage associated with disease risk. The 39 nonsmokers and 38 smokers, age 20 to 51 years, were given a daily supplement (272 mg vitamin C, 31 mg all-rac-alpha-tocopherol, and 400 micrograms folic acid), or placebo, for 90 days with their usual diet. Blood and urine were taken at baseline and at the end of the study. Urine thiobarbituric acid reactive substances (TBARS) was the only oxidant damage marker that was significantly higher in smokers compared to nonsmokers.

Supplementation significantly increased plasma ascorbate and tocopherol, indicating that the 90-day supplementation treatment was effective in increasing antioxidant status. However, the 90-day antioxidant supplementation had no effect on the oxidant biomarkers. Overall. the conclusion drawn from the present study is that moderate antioxidant supplementation of healthy young men, including smokers and those with low fruit/vegetable intakes, does not significantly reduce in vivo oxidant damage. In healthy young men, the endogenous antioxidant defense system and a modest intake of dietary antioxidants are adequate to minimize levels of in vivo oxidant damage such that they cannot be differentiated by current methods.

R Jacob, G Aiello, C Stephensen, J Blumberg, P Milbury, L Wallock, B Ames. Moderate antioxidant supplementation has no effect on biomarkers of oxidant damage in healthy men with low fruit and vegetable intake, J Nutr. 133: pp 740-743 (March 2003) [Correspondence:rjacob@whnrc.usda.gov]