Abstract
The nutritional efficiency of nicotinamide N-oxide and N'-methylmcotinamide as substitutes for nicotinic acid was investigated using weanling rats fed with a nicotinic acid-free and tryptophan-limited diet (basal diet; negative control), the basal diet containing 0.003% nicotinic acid (positive control), or basal diet containing various amounts of nicotinamide N-oxide or N'-methylnicotinamide. The relative niacin activity of nicotinamide N-oxide and N'-methylnicotinamide to nicotinic acid was about 1/5 and 1/2 on a weight basis, respectively, judged from the following comparisons: body weight gain, food intake, food efficiency ratio, the NAD contents in liver and blood, the total nicotinamide content in liver, and the urinary excretion of nicotinamide and its metabolites such as N1-methylnicotinamide, N1 -methyl-2-pyridone-5-carboxamide, and N1 -methyl-4-pyridone-3-carboxamide.
