Bioavailability of vitamin B-6 in young and older men.

Various indexes of vitamin B-6 status have been shown to be reduced with aging. The cause for the apparent reduced vitamin B-6 status is not well understood. For direct assessment of how the bioavailability of vitamin B-6 is affected by aging, [2H]pyridoxine was orally administered to healthy men, aged 20-30 and 60-70 y, who were fed a controlled diet. No differences were observed in plasma pyridoxal 5'-phosphate concentration, erythrocyte aspartate aminotransferase activity, or plasma alkaline phosphatase activity between the two age groups. There were no age-related differences in the urinary excretion of total or [2H]4-pyridoxic acid during a 3-d collection period. Results from this study indicate that the bioavailability of vitamin B-6 is not altered with aging in free-living, healthy adult men.