Nicotinamide daily requirements

See also NAD+, NADH NADP+, NADPH daily requirements 756, 769 Nicotinamide adenine dinucleotide. See NAD+, NADH... 

Nicotinamide is derived from nicotinic acid that is synthesized by human cells from the essential amino acid tryptophan. Our diet is also a rich source of nicotinamide, so the body has adapted to synthesizing much less than the daily requirements. Many commercial breakfast cereals and spreads are supplemented with nicotinamide that is usually termed niacin or vitamin B3 on their Nutrition Fact labels. 

The daily requirement (cf. Table 6.3) is covered to an extent of 60-70% by tryptophan intake. Hence, milk and eggs, though they contain little niacin, are good foods for prevention of pellagra because they contain tryptophan. It substitutes for niacin in the body, with 60 mg L-tryptophan equalling I mg nicotinamide. Indicators of sufficient supply of niacin in the diet are the levels of metabolites II (cf. Formula 6.13) in urine or III and IV in blood plasma. 

The Federal Enrichment Act of 1942 required the millers of flour to restore iron, niacin, thiamin and riboflavin lost in the milling process. Enriched flours and baked goods made from them are now excellent sources of niacin. Niacin may also be found in meat, poultry, fish, whole grains, and peanut butter. Besides direct niacin intake, humans can convert the amino acid tryptophan to niacin. Many people take daily vitamin supplements to ensure they get enough niacin and other essential nutrients, see also Coenzyme Nicotinamide Adenine Dinucleotide. 

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