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Quel est le rôle de la Vitamine B3 ?

Niacin, or vitamin B3 , is a water-soluble B vitamin found naturally in some foods, added to foods, and sold as food supplements. The two distinct forms of niacin in foods and dietary supplements are nicotinic acid as well as nicotinamide. The body can also convert the amino acid tryptophan into nicotinamide. Niacin is water soluble, so excess amounts the body does not need are excreted in urine. Niacin functions in the body as a coenzyme, with more than 400 enzymes depending on it for various reactions. Niacin helps convert nutrients into energy, create cholesterol and fats, create and repair DNA, and exert antioxidant effects.

What are the recommended amounts of Vitamin B3?

AJR : Niacin is measured in milligrams (mg) of niacin equivalents (EN). One NE is equivalent to 1 milligram of niacin or 60 mg of tryptophan. The Recommended Dietary Allowance (RDA) for adults 19 years and older is 16 mg EN for men, 14 mg EN for women, 18 mg EN for pregnant women, and 17 mg EN EN for breastfeeding women.

AMT : The tolerable upper intake level is the maximum daily intake that is not likely to cause adverse health effects. The UL for niacin for all adults over 19 is 35 milligrams.

Food sources

Niacin deficiency is rare because it is found in many foods, both animal and plant-based.

  • Red meat: beef, beef liver, pork
  • Poultry
  • Fish
  • Brown rice
  • Enriched cereals and breads
  • Nuts, seeds
  • Legumes
  • Bananas

Food supplements

Niacin is available in supplement form as nicotinic acid or nicotinamide. Sometimes the amounts in supplements are much higher than the RDA, causing unpleasant side effects like hot flashes. Niacin supplements are also available as a prescription medication to treat high cholesterol; This is usually a time-release form of nicotinic acid that allows for slower, more gradual absorption, so it does not cause flushing. Due to the very high doses of nicotinic acid required, up to 2,000 mg per day, this supplement should only be used under the supervision of a doctor.

Read also: What is the role of Iron?

Signs of deficiency and toxicity


Niacin deficiency is rare in the United States and other industrialized countries because it is well absorbed from most foods (with the exception of some cereal grains in which niacin is bound to its fiber, reducing it absorption) and is added to many foods and multivitamins. Severe niacin deficiency leads to pellagra, a condition that causes a dark, sometimes scaly rash on sun-exposed areas of the skin, bright redness of the tongue, and constipation/diarrhea. Other signs of severe niacin deficiency include:

  • Depression
  • Headache
  • Fatigue
  • Memory loss
  • Hallucinations

Groups at risk of deficiency

Limited diets. People whose diets are limited in the variety and quantity of foods, such as those who live in poverty or who are very ill and cannot eat a balanced diet, are at increased risk. Developing countries that primarily consume corn are at risk of pellagra because these foods are low in absorbable niacin and tryptophan. Chronic alcoholism. The absorption of several nutrients, particularly water-soluble vitamins, including those of the B family, is reduced in cases of excessive alcohol consumption.

Carcinoid syndrome. It is a disease of slow-growing cancer cells in the intestine that release a chemical called serotonin. This syndrome causes tryptophan in the diet to be transformed into serotonin rather than niacin, which increases the risk of low niacin.


Toxicity during consumption of foods containing niacin is very rare, but it is possible. It can occur during long-term use of high-dose food supplements. Reddened skin with itching or tingling on the face, arms, and chest is a common sign. Flushing occurs primarily when taking high-dose supplements in the form of nicotinic acid, rather than nicotinamide.

Other signs:

  • Dizziness
  • Low blood pressure
  • Fatigue
  • Headache
  • Stomach ache
  • Nausea
  • Vision problems
  • Impaired glucose tolerance and liver inflammation in severe cases (at very high doses of 3,000 to 9,000 mg daily for several months/years).

Vitamin B3: Did you know?

Many B vitamins are thought to help increase energy, including niacin. Because niacin is water soluble (which reduces the risk of it accumulating in the body to a toxic level), many people do not hesitate to take a supplement that may contain 100 times the RDA of this vitamin . Although niacin helps several enzymes convert food into ATP, a form of energy, taking doses well above the RDA will not provide a particular energy boost. It is often enough to adopt a balanced diet consisting of a variety of foods to benefit from the beneficial effects of niacin on energy.

Corn is naturally rich in niacin , but it is bound to carbohydrates, making it difficult for the human body to absorb. However, when corn is nixtamalized (a traditional tortilla-making process where the corn is treated with calcium hydroxide, cooked, and ground), niacin becomes absorbable through the calcium hydroxide treatment.

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