Define the effect of Vitamins (A, D, K and B-Complex) on athletes?

Vitamins A, D and K have been found to have no ergogenic effects. Ingesting large doses of these vitamins have toxic effects. Most scientific evidence shows that B-complex supplementation seldom enhances performance. In fact, high doses of niacin (>SO mg) can cause flushing. Thus, supplementation with single B vitamin or a mixture of B vitamin supplementation have more effects on mental performance than physical performance and only gives the sense of 'feeling better'.