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Niacin Deficiency

Niacin deficiency is a condition that occurs when a person doesn't get enough or can't absorb niacin or tryptophan.

Also known as vitamin B3 or nicotinic acid, niacin is one of eight B vitamins. Like all B vitamins, niacin plays a role in converting carbohydrates into glucose, metabolizing fats and proteins, and keeping the nervous system working properly. Niacin also helps the body make sex- and stress-related hormones and improves circulation and cholesterol levels.

Tryptophan is one of the amino acids that makes up protein. Your liver can convert tryptophan from high-protein foods like meats and milk into niacin.

Niacin Deficiency Symptoms

Symptoms of mild niacin deficiency include:

  • indigestion
  • fatigue
  • canker sores
  • vomiting
  • depression

Severe deficiency, called pellagra, can cause symptoms related to the skin, digestive system, and nervous system. They include:

  • thick, scaly pigmented rash on skin exposed to sunlight
  • swollen mouth and bright red tongue
  • vomiting and diarrhea
  • headache
  • apathy
  • fatigue
  • depression
  • disorientation
  • memory loss

If not treated, pellagra can lead to death.

Niacin Deficiency Causes

In the 1800s, pellagra was common among poor Americans whose diets consisted mostly of corn, molasses, and salt pork -- all poor sources of niacin. Today, most people in the developed world get plenty of niacin in their diets. Niacin deficiency is more likely to be caused by problems that affect absorption of niacin or tryptophan. The most common cause is alcoholism. Other possible causes include disorders of the digestive system and prolonged treatment with the tuberculosis drug isoniazid (Laniazid, Nydrazid).

Niacin Deficiency Treatments

The recommend daily allowance (RDA) for niacin is 16 milligrams per day for men and 14 milligrams per day for women. For most people, a diet rich in niacin will prevent niacin deficiency. Good sources of niacin include red meat, fish, poultry, fortified breads and cereals, and enriched pasta and peanuts.

If you don't eat a lot of niacin-rich foods or if you have a medical condition that affects the absorption of niacin or tryptophan, speak to your doctor. Niacin supplements or multivitamin/mineral supplements, which usually contain at least 20 milligrams of niacin, can help prevent niacin deficiency.

Supplements of niacin such as nicotinic acid or nicotinamide are approved by the FDA for treating niacin deficiency. Under the supervision of a doctor, high doses of over-the-counter or prescription nicotinic acid can be used to treat high cholesterol. However, too much nicotinic acid can be harmful. Avoid taking more than your doctor prescribes or recommends. If you are taking doses of more than 100 milligrams per day, doctors recommend periodic liver function tests.

WebMD Medical Reference

Reviewed by Kimball Johnson, MD on October 13, 2012

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