Acute changes in vitamin B6 status in endurance athletes before and after a marathon.

The vitamin B6 status of 13 endurance athletes was determined by whole blood B6 (microbiological) and urine 4-pyridoxic acid (4-PA) (HPLC), serum vitamin B6 (pyridoxal, pyridoxol, pyridoxamine) (HPLC), and erythrocyte alpha-EGOT measurements with the aid of 7-day records. In addition, blood and serum samples and urine were collected before (Time A), directly after (Time B), and 2 hr after a marathon race (Time C). The total energy intake was 12,303 +/- 3,464 kJ/day (34% fat, 48% carbohydrates, 14% protein). The vitamin B6 intake, serum concentrations, alpha-EGOT value, and 4-PA excretion were higher than the reference values at Time A. Only the vitamin B6 whole blood levels were below the normal level at Time A. The vitamin B6 status of the athletes corresponded essentially to reference values obtained for untrained individuals. There was a mean loss of about 1 mg vitamin B6 as a result of the marathon race. Vitamin B6 supplementation does not appear necessary if a balanced diet is consumed.