The daily requirement is about 20 mg from the diet and synthesis from tryptophan in the body. A deficiency of this vitamin results in pellagra. There are such communities which eat only corn or maize which is deficient in tryptophan therefore this community could be suspectible to pellagra
Pellagra should not be missed as this rash is symmetrical. There is a sign which is known to be caused by niacin deficiency It is called Casal’s necklace . This is a broad band collar of dermatosis right around the neck and can extend downwards.
The dermatosis of pellagra is classic ( usually the back of the hands and fingers are affected.)