Total radical-trapping antioxidant potential (TRAP) of plasma: effects of supplementation of young healthy volunteers with large doses of alpha-tocopherol and ascorbic acid.

A randomized, placebo-controlled double-blind supplementation trial was conducted on 32 adults to assess the effect of dl-alpha-tocopherol (1 g/day for 28 days) or ascorbic acid (AA) (1 g/day for 28 days) separately or in combination on the total radical-trapping antioxidant potential (TRAP) of plasma. Subjects were divided into 4 groups of 8 and received the following: Group 1, placebo; Group 2, ascorbic acid; Group 3, alpha-tocopherol; Group 4, alpha-tocopherol and AA. Antioxidant potential was assessed using the TRAP technique (a specific measure of the capacity of the secondary antioxidants, vitamins E, C, reduced thiol compounds and urate in plasma to resist controlled in vitro peroxidation). TRAP values were estimated at baseline and after treatment (day 29). Group means of the antioxidant vitamins at baseline were within normal values for both ascorbic acid (62-82 mumol/l) and alpha-tocopherol (24-29 mumol/l). Despite marked increases post-supplementation in plasma alpha-tocopherol levels in Groups 3 (94%) and 4 (91%) and in AA levels in Groups 2 (82%) and 4 (32%), there were no significant differences (analysis of variance) between the 4 treatment groups for TRAP values on day 29. Paired-t-testing revealed significant (P < 0.01) increases in post-supplementation TRAP values in Groups 2 and 3.