Vitamin E supplementation, exercise and lipid peroxidation in human participants.

The theoretical benefits of using antioxidant vitamin supplements to quench oxygen free radicals appear large. The major function of vitamin E is to work as a chain-breaking antioxidant in a fat soluble environment so as to protect polyunsaturated fatty acids within membrane phospholipids and in plasma lipoproteins. The purpose of this critical review was to determine whether vitamin E supplementation decreases exercise-induced lipid peroxidation in humans. If vitamin E alone is ineffective, researchers can turn their efforts to other individual antioxidants or combinations. Using the search words "vitamin E", "exercise", "lipid peroxidation" and "antioxidant", all relevant studies since 1985 were identified through a computer search using Pub Med and Sport Discuss databases. Additional articles were reviewed from the reference list of the retrieved articles. Nine vitamin E studies met the criteria of using human participants in an experimental design. Studies were analyzed to determine the strength of evidence regarding the efficacy of vitamin E supplementation. Strength of evidence was based on: (1) number of participants, (2) intensity of the exercise test, (3) type of research design, (4) other controls, (5) the biomarker of lipid peroxidation, (6) the timing of the biomarker measurement, (7) measurement of vitamin E status and (8) correction for plasma volume change. Overall, the six studies showing no effect of vitamin E supplementation had a much higher total score (67) in comparison to the three studies showing positive effects (38). Although limitations have plagued much of the research, vitamin E supplementation does not appear to decrease exercise-induced lipid peroxidation in humans.