Observations on Induced Riboflavin Deficiency and the Riboflavin Requirement of Man

Abstract

Four subjects were maintained for 288 days on a standard diet containing only 0.35 mg. of riboflavin per 1000 calories but made adequate in other factors of the vitamin B complex by addition of them in crystalline form. The only evidence of deficiency observed was progressive decrease of excretion of a test dose of 2.0 mg. of sodium riboflavin, indicating progressive depletion of tissue stores of riboflavin. However, in view of the gradual depletion of stores it may be assumed that if this degree of restriction had been continued for a longer period of time, clinical evidence of riboflavin deficiency eventually would have appeared. Two subjects were maintained on the same standard diet for a period of 246 days but these subjects did not receive supplements of crystalline vitamins and therefore the deficiency involved all factors of the B complex. This moderately severe restriction of the B complex did not produce the clinical syndrome of riboflavin deficiency. However, again a gradual depletion of stored riboflavin was indicated by a progressive decrease of excretion of test doses of riboflavin. Two subjects maintained on the same standard diet for a period of 288 days were given crystalline riboflavin in addition to other vitamins of the B complex. Evidence of deficiency of any kind was not observed. Variation of the intake of crystalline riboflavin supplement and determination of excretion of test doses of riboflavin provided evidence that an intake of 0.8 mg. of riboflavin per 1000 calories was not associated with depletion of tissue stores of riboflavin, whereas an intake of 0.35 mg. per 1000 calories definitely was so associated. An intake of 0.5 mg. per 1000 calories appeared to be close to the daily requirement necessary for maintenance of satisfactory tissue stores of riboflavin. This value therefore (0.5 mg. per 1000 calories) appears closely to approximate the minimal daily requirement for riboflavin.