Vitamin B-6 metabolism as affected by exercise in trained and untrained women fed diets differing in carbohydrate and vitamin B-6 content.

To assess the effect of exercise on vitamin B-6 metabolism in women, five young-trained, five young-untrained, and five postmenopausal-untrained women were alternately fed four diets and then exercised (80% VO2 max; 20 min) after each diet. The following diets were fed: 2 wk moderate carbohydrate (CHO) (49%) (2.3 mg B-6); 1 wk high CHO (64%) (2.4 mg B-6); 2 wk moderate CHO + B-6 (10.3 mg B-6); 1 wk high CHO + B-6); 1 wk high CHO + B-6 (10.4 mg B-6). Blood was drawn pre- and postexercise and post-30 min and post-60 min of exercise and analyzed for plasma pyridoxal 5'-phosphate (PLP) and total B-6. Twenty-four-hour urines were analyzed for 4-pyridoxic acid and urinary B-6. PLP and total B-6 increased significantly with exercise and decreased significantly from post- to post-60 min for all diets. Four-pyridoxic acid increased significantly from the preexercise day to the day of exercise for all diets. Although there was a significant change in B-6 metabolism with exercise, neither training, increased CHO, nor age had an effect on this change.