Effect of vitamin B-6 supplementation on fuels, catecholamines, and amino acids during exercise in men.

Purpose: In two separate but identical studies, the effect of vitamin B-6 supplementation was examined on plasma energy substrates, catecholamines, and 13 amino acid concentrations during exercise. Methods: Eleven trained men performed two separate exhaustive exercise tests at 71.0 ± 4.6% VO 2max during two separate 9-d controlled diet periods. Exercise test I (TIC) occurred following a control diet, and test 2 (T2B6) occurred following a vitamin B-6 supplemented diet (20 mg PN.d -1 ). Blood was drawn pre, during (60 min), post, and post-60 min of exercise. and plasma was analyzed for glucose, lactate, glycerol, free fatty acids (FFA), catecholamines (N = 5), and amino acids (N = 5). Results: Mean FFA concentrations changed over time in both tests (P < 0.001) and were lower in T2B6 compared to TIC at pre (P = 0.03), during (P = 0.05), and post-60 min (P = 0.04) of exercise. Mean lactate, glycerol, and catecholamine concentrations only changed over time (P < 0.0001). The only significant changes in amino acid concentrations were for lower tyrosine (P = 0.007) and methionine (P = 0.03) concentrations in T2B6 relative to TIC at post-60 min of exercise and postexercise, respectively. No differences were observed in exercise times to exhaustion between TIC (108+32.6 min) and T2B6 (109+51.2 min). Conclusions: These results indicate that vitamin B-6 supplementation can alter plasma FFA and amino acid concentrations during exhaustive endurance exercise without affecting endurance.