Vitamin B3 (niacin)

Vitamin B3 is a water-soluble vitamin which refers in fact to two compounds: nicotinic acid (niacin) and nicotinamide.
We usually use the term niacin for this vitamin, but those two compounds have the same biological activity. However, nicotinic acid taken in large doses can cause "niacin flush"; a burning, itching feeling in the face, neck, arms or chest.

Niacin is a unique vitamin since it can be synthesized from tryptophan, one of the essential amino-acids.
It takes 60 g of tryptophan to make 1 g of niacin provided that the intestinal flora is healthy and the diet contains sufficient amounts of vitamins B2, B6 and proteins.

For these reasons, niacin's recommended intake is expressed as niacin equivalents (NE).
1 niacin equivalents (NE) = 1 mg of niacin or 60 mg of tryptophan.

Niacin derivatives are part of two coenzymes: NAD (nicotinamide adenine dinucleotide) and NADP (nicotinamide adenine dinucleotide phosphate). Those two coenzymes are necessary to many oxidation-reduction reactions that are vital in cell metabolism.

Niacin is vital for all our body cells. It participates in many metabolic functions which are important in the release of energy from nutrients, especially carbohydrates but also fats and proteins. This vitamin is our cells' supplier of energy.

Niacin promotes a healthy nervous system and normal mental function.

It improves blood circulation and lowers cholesterol and triglycerides. This vitamin is therefore needed for the proper function of the circulatory system. Studies suggest that niacin reduces the recurrence rate for heart attacks by almost 30 percent.

Niacin also assists in antioxidant and detoxification functions. It is used in the treatment of arthritis.

Finally, niacin is essential for the synthesis of hormones such as estrogen, progesterone, testosterone, insulin...


Recommended Dietary Allowance (RDA)
mg per day
Babies 0 to 1 year
Children 1 to 3 years
Children 4 to 6 years
Children 7 to 9 years
Teenager 10 to 12 years
Teenager boys 13 to 15 years
Teenager girls 13 to 15 years
Teenager boys 16 to 19 years
Teenager girls 16 to 19 years
Pregnant women
Nursing mothers

Deficiency symptoms
First signs of deficiency are skin irritations, muscle weakness, fatigue, dizziness, loss of appetite, headaches, red tongue, nausea and vomiting...

A chronic deficiency in niacin leads to pellagra. This disease occurs especially in population where corn is the main food in the diet. This is due to the fact that niacin in the corn is not well assimilated and because corn protein is also deficient in tryptophan.

Pellagra is characterized by the 3Ds: Dermatitis, Diarrhea, and Dementia. If not treated this disease could be lethal.

Although rare in developed countries, pellagra is still a common disease in parts of Asia and Africa.

Who is at risk?
People who might be deficient are those who have:

  1. A poor diet
  2. Hyperthyroidism
  3. Diabetes mellitus
  4. Alcoholism
  5. Gastrointestinal problems such as cancer
  6. Cirrhosis
  7. Hartnup disease (a rare disease due to abnormal absorption and excretion of tryptophan and other amino acids)

Good vegetarian sources

  1. Brewer's yeast
  2. Peanuts
  3. Peanut butter
  4. Sesame seeds
  5. Tahini (sesame butter)
  6. Sunflower seeds
  7. Wheat germ and bran
  8. Sprouted wheat
  9. Avocado
  10. Mushrooms
  11. Green peas
  12. Whole cereals
  13. Cold water fishes *

*For those who eat fishes.

Niacin can be toxic if taken in excess. High doses of niacin can cause liver damage, gastric irritation, nausea, vomiting, abdominal cramps, diarrhea...

Do not take supplements without asking your doctor first.

Realized by Laurence LIVERNAIS-SAETTEL, Dietitian.
© Copyright L. Livernais-Saettel 2000
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