Define Criteria for Assessment of Niacin Status?
Niacin status can be monitored by daily urinary excretion of methylated metabolites, especially the ratio of the 2-pyridone to N'-methyl-nicotinmide, erythrocyte pyridine nucleotides, oral dose uptake tests, erythrocyte NAD, and plasma 2-pyridone.
Excretion of N-methyl nicotinamide in urine after an oral niacin load of 20 mg nicotinamide70 kg body weight over 24 hours is measured and levels of 4.8 m mol/dl represents deficiency and 5.8-17.5 m mol/dl represents low niacin status. Shibata and Matsuo suggest that the ratio of urinary 2-pyridone to NJ-methyl- nicotinamide .is as much a measure of protein adequacy as it is a measure of niacin status. The ratio of the 2- pyridone to N'-methyl-nicotinamide also appears to be associated with the clinical symptoms of pellagra, principally the dermatilic condition. In plasma, 2-pyridone levels change in reasonable proportion to niacin intake. As in the case of the erythrocyte pyridine nucleotides (nicotinamide coenzymes), NAD concentration decreased by 70% whereas NADP remained unchanged in adult males fed diets with only 6 or 10 mg NEs/day.