The influence of antioxidant nutrients on platelet function in healthy volunteers

There is mounting evidence that antioxidants may help to prevent coronary heart disease and modulate some thrombotic events such as platelet adhesion. However, the effects of antioxidant supplementation on platelet function in vivo are controversial. A double-blind, randomised, placebo-controlled study was performed on 40 healthy volunteers (20–50 years) supplemented daily with vitamin E (300 mg), vitamin C (250 mg) or β-carotene (15 mg) for 8 weeks. Platelet function was assessed by platelet aggregation induced by ADP, arachidonic acid or collagen, platelet responsiveness to the inhibitor PGE1, β-thromboglobulin release and ATP secretion. Supplementation with vitamin E resulted in a significant increase in platelet α-tocopherol level (+68%) reflecting closely the increase in plasma α-tocopherol level (+69%). Platelet function was significantly decreased by vitamin E as revealed by the decreased platelet aggregation in response to ADP and arachidonic acid, the increased sensitivity to inhibition by PGE1, the decreased plasma β-thromboglobulin concentration and the decreased ATP secretion. Supplementation with vitamin C did not affect platelet function significantly although a trend towards a decreased platelet aggregability and an increased sensitivity to the inhibitor PGE1 were observed. No significant changes in platelet function occurred after supplementation with β-carotene. In conclusion, supplementation of healthy volunteers with vitamin E decreased platelet function whereas supplementation with vitamin C or β-carotene had no significant effects.