Experts Debunk Study on "Pro-Oxidant" Effects of Vitamin E

WASHINGTON, DC, June 25, 2001—Several notable experts on vitamin E have debunked a recent research report that claims to demonstrate a pro-oxidant effect of vitamin E. They assert that vitamin E actually protects against oxidative damage rather than promoting it. These experts concluded that the study by Richard Weinberg and colleagues (Aterioscl Thromb Vasc Biol 2001;21:1029-33), among other weaknesses, was simply inadequate because it did not include a control group.

"The Weinberg study found no evidence of an oxidative effect, and in fact confirmed a positive effect of vitamin E in extending the lag time for LDL oxidation," said Dr. Ishwarlal Jialal of the University of Texas Southwestern Medical Center in Dallas, one of the world’s premier antioxidant researchers. Dr. Jialal said this study in no way counters the strong body of evidence suggesting a benefit of vitamin E. In addition to its antioxidant effects, vitamin E has anti-inflammatory effects and decreases platelet aggregation. Both of these effects are important in reducing the risk of heart disease.

"I don’t think this study shows any pro-oxidant effect of vitamin E at all," said Dr. Maret Traber, an internationally recognized expert on vitamin E at the Linus Pauling Institute, Oregon State University. "The measurements were not made all in the same sample," she continued, "with arachidonic acid measured in LDL, isoprostanes in plasma, and LDL oxidation in a test tube." While vitamin E levels in plasma and LDL may increase rapidly following supplementation, vitamin E levels in tissues will take much longer to increase. The study simply was not long enough to allow tissue vitamin E levels to rise.

The study cannot establish whether any changes observed were related to the cumulative effects of the polyunsaturated fats given to the subjects, or to the vitamin E, or to something else entirely. Ten people were fed three different diets in succession: a diet rich in monounsaturated fat (olive oil) for 3 weeks, then a diet rich in polyunsaturated fat (PUFA = 20% calories) for three weeks, then the high-polyunsaturated fat diet plus 800 IU vitamin E for a final three weeks. This high level of PUFA far exceeds the amount found in usual diets and is twice as high as the maximum recommended in dietary guidelines. Current guidelines recommend not exceeding 10% of calories from PUFA.

"It is impossible to attribute any pro-oxidant effects to vitamin E, on the basis of this study," said Dr. John Hathcock, Vice President for Nutritional Science and Regulatory Affairs for the Council for Responsible Nutrition (CRN). "Thus, consumers should continue to have confidence in the protective effects of vitamin E against LDL oxidation, and in its recognized benefits to smokers or others under oxidative stress," continued Dr. Hathcock.

The Council for Responsible Nutrition (CRN) is a science-based, trade association founded in 1973 and represents more than 100 companies in the dietary supplement industry, including ingredient suppliers and manufacturers. CRN members adhere to a strong code of ethics, comply with dosage limits and manufacture dietary supplements to high quality standards under good manufacturing practices.