Abstract
Human urine was collected 5 hr after lunch for 3 months and the urinary excretion of N^1-methylnicotinamide (MNA) , N^1-methyl-2 pyridone-5-carboxamide (2-py) and N^1-methyl-4-pyridone-3-carboxamide (4-Py), which are used as a biochemical index of niacin nutrition, were measured by high-performance liquid chromatography. The correlation between niacin equivalent intake at lunch and each of the following items- MNA, 2-Py, 4-Py or " MNA+2-py+4-py " excretion, the 2-Py/ MNA, 4-Py/ MNA, 2-Py+4-py/ MNA or 2-Py/ 4-Py ratio was not significant. In terms of niacin equivalent intake per 1000kcal, no significant correlation was observed. The daily urinary excretions of MNA, 2-Py and 4-Py were very fluctuating even in the same individual. These results indicate that urinary excretion of MNA, 2-Py and 4-Py does not immediately change with food taken at lunch, and that these excretions would be affected by the unknown factors or by long term food intakes. But, when a large amount of nicotinamide (100mg) was administered at lunch, urinary excretion of MNA, 2-Py and 4-Py, 5 hr after lunch, increased markedly. Therefore, when these values are used as a biochemical index of niacin nutrition, it is a very dangerous to decide with only one-time value; it should be decided from the mean value of the values measured at least 4 times at intervals of one week.
