Studies of Niacin Requirement in Man II. Requirement on Wheat and Corn Diets Low in Tryptophan

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Abstract
Three subjects were maintained for 90 to 105 days on a “wheat” diet which furnished approximately 5 mg of niacin and 200 mg of tryptophan daily. One subject developed typical niacin deficiency beginning 80 days after the diet was instituted, a second developed amenorrhea, herpes of the lip and slight redness of the tongue papillae, and a third showed lassitude and depression as the only clinical findings. In contrast to this, each of three subjects previously maintained on a “corn” diet of comparable niacin and tryptophan content showed the characteristic clinical picture of niacin deficiency after about 50 days of the experimental period. Excretion of N1-methylnicotinamide decreased to lower levels within a shorter period of time, and tryptophan excretion was slightly lower during the corn than during the wheat regimen. The time at which pellagra developed, and the severity of the deficiency, seemed to be related to the intake of niacin and tryptophan per unit of body size with both the “wheat” and “corn” diets. However, this relationship may not completely explain differences in clinical and laboratory findings between the two regimens. The low tryptophan content of corn may not be the sole explanation of the pellagragenic effect of this cereal. When the “corn” diet was supplemented with varying amounts of niacinamide a significant increase in excretion of niacin metabolites occurred when the intake approximated 8 to 10 mg daily. These data suggest that with the “corn” diet, which furnishes 200 mg of tryptophan daily, body niacin stores approach adequacy when the diet supplies 8 to 10 mg of niacin.