Niacin – Vitamin B3 / P

Vitamin B3, also referred to as niacin or Vitamin P, is a water-soluble vitamin that cannot be stored in the body.

The derivative form of niacin is nicotinamide, which is used by the body in forming the coenzymes nicotinamide adenine dinucleotide (NAD), as well as the nicotinamide adenine dinucleotide phosphate (NADP).

These chemical structures should not to be associated with the nicotine found in tobacco, as they are not related although they have similar names.

Niacin Role in the Body

Vitamin B3 is one of the significant vitamins in the body that supports the metabolism of energy and reactions involving degradation and biosynthesis as part of the pyridine nucleotide coenzymes, NAD and NADP. The levels of reduced and oxidized forms of these coenzymes establish the cells’ redox potentials that regulate metabolic activities such as numerous enzyme reactions and mitochondrial electron transport.

Large amount of niacin is also used as a pharmacological agent in blood lipid-lowering therapy. Niacin has been used in lowering elevated LDL or the so-called bad cholesterol and triglyceride (fat) levels in the blood since 1950s. However, certain side effects can arise when niacin is used in these ways that are harmful to the body.

Niacin also aids in the creation of various stress-related and sex hormones in the adrenal glands and other parts of the body and it can also help improve the overall circulation of the blood in the body.

Factors Affecting Niacin Availability

Due to the fact that niacin is a water-soluble vitamin, large doses can be lost if significant volumes of liquids are used in the cooking process of food sources. It is also largely lost during the milling process of grains, which is why most rice and flour are enriched by vitamin fortification in order to compensate for such losses.

Vitamin B3 synthesis in the body

Vitamin B3 can be obtained from biosynthesis with the amino acid tryptophan as a precursor, or simply from consumption of food sources. About 60mg of tryptophan is needed in order to synthesize 1mg of niacin. The biosynthesis of niacin is highly dependent on the availability of riboflavin (vitamin B2) and pyridoxine (vitamin B6).

Niacin Deficiency

Clinical evidence of having Niacin deficiency include diarrhea, headache, poor appetite, irritability, fatigue, emotional instability and possible memory loss.

Pellagra is the late stage of niacin deficiency and has symptoms that are normally referred to as the four D’s, which are diarrhea, dermatitis, dementia, and death. The word “pellagra” came from the Italian phrase that means raw or rough skin, as under this condition, the skin becomes scaly, thick, and darkly pigmented rash develops symmetrically in areas exposed to sunlight.

Neurologic symptoms of severe niacin deficiency include fatigue, disorientation, apathy, depression, headache, and memory loss. Symptoms related to the digestive system are diarrhea, vomiting, and a bright red tongue. If untreated, pellagra is ultimately fatal.

Niacin Toxicity

When large doses are consumed, niacin toxicity can occur, although this is rarely observed.

Large amounts of nicotinic acid are used in treating high blood cholesterol, wherein histamine release can be triggered and results in flushing of the skin that is dangerous to patients who have  peptic ulcer disease or asthma. When consumed in high doses in some supplements, niacin can also trigger hepatic toxicity.

Recommended Dietary Allowance (RDA) for Niacin


FEMALES (mg/day)

MALES (mg/day)

0 to 6 months 2 AI 2 AI
7 to 12 months 4 AI 4 AI
1 to 3 years 6 6
4 to 8 years 8 8
9 to 13 years 12 12
14 to 18 years 14 16
19 years and older 14 16
Pregnancy all ages 18
Lactating all ages 17

 Food Sources of Niacin

Niacin rich foods include beef liver, tuna, salmon, chicken, turkey, ground beef, peanuts, lentils, lima beans, baked potato, almonds, mushrooms, flour tortilla, peach, carrot, sweet potatoes, pasta, barley, peanut butter, and fortified foods such as cereal.


UMM; LPI; Northwestern University; UMassMed; NIH; NIH2.