Vitamin B6Requirement for Adult Men

The results of a study with young adult male subjects has revealed that (1) a vitamin B6depletion could be rapidly achieved, as was noted by measurements of urinary xanthurenic acid excretion following the oral administration of a 10 gm. dl-tryptophan load; (2) the rate of depletion was directly related to protein intake; (3) the changes in urinary vitamin B6excretion correlate inversely with the xanthurenic acid excretion and the deficiency status; (4) the 3-hydroxykynurenine excretion was of limited use in evaluating vitamin B6requirements; and (5) the urinary oxalate excretion showed little or no change. It is concluded that the optimal daily vitamin B6requirement (as pyridoxine hydrochloride) for subjects on a high protein intake (100 gm.) appeared to be 1.75 to 2.0 mg. per day, while subjects on a low protein intake (30 gm.) appeared to have a requirement of 1.25 to 1.5 mg. per day.