Vitamin B3 is a water-soluble vitamin that cannot be stored in body fat. It has two active components, nicotinic acid (niacin) and nicotinamide (niacinamide). This vitamin plays a role in over 200 enzymatic reactions. 

The body can synthesize vitamin B3 in small amounts, provided it has sufficient stores of magnesium, vitamins B6 and B2, and tryptophan. The latter is an essential amino acid (part of a protein)—that is, it is not produced by the body and must be obtained from food sources. 

NOTE: like many other members of the vitamin B family, vitamin B3 supplements are better absorbed when taken with food. 


What does vitamin B3 do? 

It plays a role in: 

  • Red blood cell formation;
  • Oxygen transport to the cells;
  • Blood circulation;
  • Digestive system function;
  • Nervous system function;
  • Sexual hormone synthesis;
  • Neurotransmitter production.


Some people need greater amounts of niacin, especially those afflicted with Hartnup disease (a hereditary disorder associated with impaired absorption of certain amino acids), cirrhosis of the liver, carcinoid syndrome, and malabsorption syndrome. Individuals who are undergoing hemodialysis or peritoneal dialysis (two purification techniques that use an artificial filter [dialyzer] or natural filter [the peritoneum], respectively, when the kidneys can no longer purify the blood) or receiving extended treatment for tuberculosis are also likely to require greater amounts of vitamin B3, as are women who are pregnant with multiples or nursing more than one infant. 

Vitamin B3 requirements are expressed in niacin equivalents (NE). 

Recommended Dietary Allowances for Niacin: 

Age Group
Quantity (niacin equivalents in mg)*
0 to 6 months
7 to 12 months
1 to 3 years
4 to 8 years
9 to 13 years
14 years and up
14 years and up
Pregnant women
Nursing mothers

Source:; Institute of Medicine, Food and Nutrition Board, Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline 2000.

This data reflects a consensus between Canadian and U.S authorities.

*Niacin amounts are expressed in “niacin equivalents” (NE): 1 mg NE = 60 mg of tryptophan = 1 mg of niacin.

**Lacking sufficient scientific evidence, authorities have established adequate intake (AI) amounts rather than recommended dietary allowances (RDAs) for this age group. Adequate niacin intake is based on observed average intakes in North American babies in good health.


Foods that are rich in vitamin B3 (niacin) include meat, liver, poultry, fish, enriched and wholegrain breads and baked goods, as well as enriched ready-to-eat cereals. 

Food Sources for Vitamin B3 (Niacin): 

Portion Sizes
Vitamin B3 (niacin)
Sautéed or braised beef, lamb, or veal liver
100g (3½oz)
Roasted chicken (white meat, with or without skin)
100g (3½oz)
Dried and salted Atlantic cod
100g (3½oz)
Sautéed milk-fed veal cutlet
100g (3½oz)
Poached salmon
100g (3½oz)
Canned tuna
100g (3½oz)
Baked or grilled yellowfin tuna or swordfish
100g (3½oz)
Sautéed or braised veal leg, loin, or shank
100g (3½oz)
Smoked sturgeon
100g (3½oz)
Grilled domestic duck (without skin)
100g (3½oz)
Baked bluefin tuna, Spanish (striped) mackerel, king mackerel, salmon
100g (3½oz)
Baked shad
100g (3½oz)
Grilled Spanish mackerel
100g (3½oz)
Roasted Canada goose thigh, with skin
100g (3½oz)
Braised or roasted rabbit
100g (3½oz)
Dry- or oil-roasted peanuts
60ml (1/4 tasse)
All-bran breakfast cereals
30g (1oz)
Grilled pork, assorted cuts
100g (3½oz)
Grilled haddock
100g (3½oz)
Raw or steamed Pacific oysters
100g (3½oz) (2 à 4 moyennes)

Source:; Health Canada, Canadian Nutrient File, versions 2001b and 2005; United States Department of Agriculture (USDA), National Nutrient Database for Standard Reference.


Vitamin B3 (niacin) deficiency is rare in developed nations, where protein-rich foods are common. A deficiency may be due to a lack of vitamin B6, which the body requires in order to convert tryptophan to niacin. Alcoholics may also suffer from vitamin B3 deficiencies because alcohol inhibits the absorption of this vitamin at the intestinal level. 

Signs of vitamin B3 deficiency: 

  • Numbness of the hands and feet;
  • Headaches;
  • Vertigo (dizziness);
  • Loss of appetite;
  • Skin hypersensitivity when exposed to the sun;
  • Inflammation of the mouth and tongue;
  • Mood swings;
  • Severe diarrhea and delirium (extreme deficiency).

Pellagra is a disease resulting from severe niacin deficiency. It is characterized specifically by the following clinical signs and symptoms: 

  • Erythema (redness of the skin);
  • Vomiting, constipation, or diarrhea;
  • Bright red tongue;
  • Depression;
  • Apathy (lack of energy);
  • Headache;
  • Fatigue;
  • Memory loss.

Adverse effects

Large doses of vitamin B3 should be taken for therapeutic purposes only under medical supervision. Blood tests must be administered regularly to assess the patient’s liver function, in view of the many adverse reactions reported and the numerous medical interactions that are possible. 

Signs of excess vitamin B3: 

  • Hot, flushed sensation in the face and neck;
  • Nausea and vomiting;
  • Impaired glucose tolerance (possible);
  • Vision problems;
  • Rashes;
  • Headache;
  • Temporarily elevated liver enzymes, a source of liver toxicity (This is extremely controversial, with some professionals believing that liver toxicity from B3 is very rare and reversible.)


  • Alcoholic;
  • Afflicted with liver dysfunction or disease;
  • Suffering from gout;
  • Suffering from gastric ulcers.


Natural health products or vitamin supplements:
It is theoretically possible that high doses of niacin, which lower cholesterol rates, may exacerbate the effects of plant components purported to do the same, such as: 

  • Garlic;
  • Resin from the guggul (a thorny shrub);
  • Psyllium;
  • Phytosterols (elements occurring naturally in plant oils which inhibit the intestines’ absorption of cholesterol).


  • Drug interactions with niacin are common. Talk to your pharmacist, who will be able to tell you whether niacin can have an effect on the medications you take.

Additional information

Vitamin B3 should never be self-prescribed, as adverse reactions occur frequently and are potentially dangerous. 

Other names

Vitamin B3, Niacin, Nicotinic acid, Nicotinamide, Vitamin PP