Correlation between niacin equivalent intake and urinary excretion of its metabolites, N'-methylnicotinamide, N'-methyl-2-pyridone-5-carboxamide, and N'-methyl-4-pyridone-3-carboxamide, in humans consuming a self-selected food.

N'-methyl-4-pyridone-3-carboxamide (4-py) is the major metabolite of nicotinamide and nicotinic acid in rats. However, because it is complicated to determine 4-py in humans, there is only one report on its excretion. Recently we developed a method for the microdetermination of 4-py by high-performance liquid chromatography. Urinary excretion of 4-py in Japanese students from Teikoku Women's University who consumed self-selected foods was 7.12 +/- 3.25 mumol/d, which is about one-fourth of N'-methylnicotinamide (MNA) and about one-ninth of N'-methyl-2-pyridone-5-carboxamide (2-py) excretion. The correlation coefficient between daily niacin equivalent (NE) intake and daily 4-py excretion was 0.529, which was about the same as the correlation coefficient between daily NE intake and daily 2-py excretion and which was two times higher than the correlation coefficient between daily NE intake and daily MNA excretion.