American Journal of Clinical Nutrition, Vol 60, 552-558, Copyright © 1994 by The American Society for Clinical Nutrition, Inc

ORIGINAL RESEARCH COMMUNICATIONS

Exercise-induced changes in plasma vitamin B-6 concentrations do not vary with exercise intensity

PG Crozier, L Cordain and DA Sampson
Department of Exercise and Sports Science, Colorado State University, Fort Collins 80523.

This study examined the effect of high vs moderate exercise intensity on changes in concentration of plasma pyridoxal 5'-phosphate (PLP), pyridoxal (PL), and 4-pyridoxic acid (4-PA) in human subjects. Eight physically active subjects were tested twice at 60% and 85% maximum oxygen consumption (VO2max) for 30 and 20 min, respectively, on a bicycle ergometer. Blood samples were obtained before and during exercise. Data were adjusted for changes in plasma volume calculated from changes in hematocrit. PLP concentrations significantly increased during exercise (P < 0.0001), with 79% of the rise in PLP concentration occurring within 5 min. 4-PA concentration increased steadily through exercise and was 23% higher at 20 min than at 0 min. Exercise intensity had no effect on the magnitude or rate of either increase for either PLP or 4-PA. PL concentration did not vary with exercise duration, but was significantly higher at 60% compared with 85% VO2max (P = 0.001). No significant differences were observed in glucose concentration. The data do not support hypotheses in the literature that PLP concentration rises during exercise to support exercise-induced shifts in substrate utilization.

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