Niacin (vitamin B3) is a water-soluble B vitamin and like other B vitamins, it helps to increase energy.
Niacin acts as a coenzyme and more than 400 enzymes are involved in the various reactions and are dependent on it. [1,2]
It comes in two forms in food and supplements, being nicotinic acid and nicotinamide.
Plant-based foods provide less niacin per serving than animal-based foods.
In some grain products especially, bioavailability reduces due to the presence of certain anti-nutrients and only 30 % of niacin becomes available, hence many of the bread, cereals and flours are fortified with niacin. 
- Niacin is absorbed primarily in the small intestine, but some are absorbed in the stomach, even at high doses of 3–4 g. 
- The absorption rate varies between 23 and 70 %; it is lowest from cereals and highest from animal products. [5,6]
- Excess niacin might be taken up by red blood cells to form a circulating reserve pool. 
- Being a water-soluble vitamin, only essential levels of niacin are stored in various body tissues. 
- Excess or unmetabolised niacin is excreted in the urine. 
- Excretion rates in adults of more than 17.5 micromol/day reflect adequate niacin status and when excretion rates are less than 5.8 micromol/day it indicates niacin deficiency. [1,3]
Recommended Daily Intake
Niacin deficiency leads to a disease called pellagra that has the following symptoms –
Niacin Food Sources
Excessive Intake/ Toxicity Side Effects
Groups At Risk of Riboflavin Deficiency
Niacin Interaction With Other Nutrients
- Iron – As with the vitamin B2 and B6, inadequate intake can also impact niacin levels [2,3].
- Certain B-vitamins – Inadequate intake of vitamin b2 and vitamin b6 may impact niacin status as the enzymes used to convert tryptophan to niacin depend on these nutrients [1,2].