STUDIES OF NIACIN REQUIREMENT IN MAN. I. EXPERIMENTAL PELLAGRA IN SUBJECTS ON CORN DIETS LOW IN NIACIN AND TRYPTOPHAN 1

Early attempts to estimate human niacin requirement were based on calculations of the niacin content of pellagragenic and nonpellagragenic diets (1, 2). It was appreciated that the protein content of the diet was in some way related to niacin requirement. Recent studies showing that the amino acid tryptophan is converted in part to niacin compounds in man (3-5) may explain the above relationship, and also the pellagra preventive effect of foods which are low in niacin but rich in good protein. The present experiments were designed to study niacin requirement in man with diets of known tryptophan content. Estimation of minimum tryptophan requirement for nitrogen balance (6) permits formulation of diets containing little excess tryptophan which may be converted to niacin. The discovery of the major metabolites of niacin, namely Nl-methylnicotinamide (N'-Me) and the 6-pyridone of Nl-methylnicotinamide (pyridone), and the development of methods for the measurement of these compounds in urine, now permit more complete studies of niacin metabolism (7-11).