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The purpose of this study was to measure plasma B-6 vitamers, and other factors which may affect the plasma concentrations of these vitamers under extreme physical conditions. Blood samples were drawn from 8 men and 3 women (43.7 ± 8.6 years) 30 min prior to the start of a 50-km ultramarathon race (pre), and at 5 (PST) and 60 (PST60) min post race. HPLC was used to measure plasma pyridoxal 5’-phosphate (PLP), pyridoxal (PL), pyridoxine (PN), and 4-pyridoxic acid (4-PA). Plasma glucose, albumin, lactate, and alkaline phosphatase activity, as well as hematocrit, and hemoglobin levels were measured. Food and liquid intake was assessed during the run. There was a significant (p < .001) decrease in the plasma PLP concentration between pre and PST, with a mean decrease of 12.9 ± 8.8 nmol/L (31% decrease). At PST60, there was a further decrease in plasma PLP concentration bringing the total decrease to 17.9 nmol/L (44%). The plasma TB6 concentration also decreased after the run, but the mean decrease was only 13.5 nmol/L (pre to PST60). PL increased 25% after the run, and did not change further at PST60. The mean plasma 4-PA concentration increased 21% post run and decreased to just below the pre-run value 1 hr post race. The plasma PLP decrease measured in the current study is not consistent with what has previously been reported during shorter length endurance studies.

This paper presents an overview of vitamin ${\text{B}}_6$ and exercise, including the role that vitamin ${\text{B}}_6$ plays in gluconeogenesis and glycogenolysis and changes in vitamin ${\text{B}}_6$ metabolism during exercise. The dietary vitamin ${\text{B}}_6$ intakes of athletes are also reviewed. Most studies report that male athletes have adequate dietary intakes of vitamin ${\text{B}}_6$ , whereas some females, especially those with low energy intakes, appear to have low vitamin ${\text{B}}_6$ intakes. Few studies have assessed the vitamin ${\text{B}}_6$ status of nonsupplementing athletes using the recommended status criteria. The role that vitamin ${\text{B}}_6$ may play in attenuating the rise in plasma growth hormone observed during exercise is also reviewed. Finally, recomrnendations are given for further research in the area of vitamin ${\text{B}}_6$ and exercise.

The vitamin ${\text{B}}_6$ status of 13 endurance athletes was determined by whole blood ${\text{B}}_6$ (microbiological) and urine 4-pyridoxic acid (4-PA) (HPLC), serum vitamin ${\text{B}}_6$ (pyridoxal, pyridoxol, pyridoxamin) (HPLC), and erythrocyte α- 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 Wday (34% fat, 48% carbohydrates, 14% protein). The vitamin ${\text{B}}_6$ intake, serum concentrations, α-EGOT value, and 4-PA excretion were higher than the reference values at Time A. Only the vitamin ${\text{B}}_6$ whole blood levels were below the normal level at Time A. The vitamin B, status of the athletes corresponded essentially to reference values obtained for untrained individuals. There was a mean loss of about 1 mg vitamin ${\text{B}}_6$ as a result of the marathon race. Vitamin ${\text{B}}_6$ supplementation does not appear necessary if a balanced diet is consumed.