Production Biosynthesis thumb|300px|class=skin-invert-image|Niacin, serotonin (5-hydroxytryptamine), and melatonin biosynthesis from tryptophan In addition to absorbing niacin from diet, niacin can be synthesized from the essential amino acid tryptophan, a five-step process with the penultimate compound being quinolinic acid (see figure). Some bacteria and plants utilize aspartic acid in a pathway that also goes to quinolinic acid. For humans, the efficiency of conversion is estimated as requiring 60mg of tryptophan to make 1mg of niacin. Riboflavin, vitamin B6 and iron are required for the process. Pellagra is a consequence of a corn-dominant diet because the niacin in corn is poorly bioavailable and corn proteins are low in tryptophan compared to wheat and rice proteins.
Production Biosynthesis thumb|300px|class=skin-invert-image|Niacin, serotonin (5-hydroxytryptamine), and melatonin biosynthesis from tryptophan In addition to absorbing niacin from diet, niacin can be synthesized from the essential amino acid tryptophan, a five-step process with the penultimate compound being quinolinic acid (see figure) Some bacteria and plants utilize aspartic acid in a pathway that also goes to quinolinic acid. For humans, the efficiency of conversion is estimated as requiring 60mg of tryptophan to make 1mg of niacin. Riboflavin, vitamin B6 and iron are required for the process. Pellagra is a consequence of a corn-dominant diet because the niacin in corn is poorly bioavailable and corn proteins are low in tryptophan compared to wheat and rice proteins.