Studies of Niacin Requirement in Man

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Abstract
Four subjects were maintained for six experimental periods on corn diets low in niacin and tryptophan. In three experiments, the corn was treated with lime prior to incorporation in the diet; in three, the corn was untreated. In two experiments with each type of corn, the subjects developed typical niacin deficiency beginning 4 to 6 weeks after the diet was instituted. In the other two studies, mild signs suggesting niacin deficiency appeared after about two months but failed to progress. Urinary excretion of N1-methylnicotinamide and the 6-pyridone of N1 Me decreased to approximately the same minimal levels after the same length of time during both dietary regimens. Likewise, excretion of tryptophan and quinolinic acid differed little during administration of the two types of corn. Under the conditions of these experiments, lime treatment of corn failed to influence the production of experimental pellagra. Excretion of quinolinic acid and tryptophan was unusually high during the early rehabilitation period in one subject. Similar findings have been encountered previously in endemic pellagra. Pellagra was induced more rapidly with diets containing Guatemalan whole corn than with diets containing unenriched milled corn obtained in the United States. This observation might be explained by the presence of substances in the bran or germ layer of corn which influence the pellagragenic effect of this cereal. The simplest explanation for the high incidence of pellagra in association with corn diets is their low niacin and tryptophan content. Findings reported here, and others published previously, suggest that additional factors may be operative.

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