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You are here : 3-RX.com > Medical Encyclopedia > Diet and Nutrition > Vitamin B3
      Category : Health Centers > Food, Nutrition, and Metabolism

Vitamin B3

Alternate Names : Niacin, Nicotinic Acid, Nicotinamide

Overview & Description | Functions and Sources

Niacin is a water-soluble vitamin. It is one of the eight B complex vitamins. These include vitamins B1, B2, B6, B12, folate, biotin, and pantothenic acid. Water-soluble vitamins are not stored in the body.


In the early 1900's, a disease called pellagra was common in the southern United States. At this time, corn was a staple of the diet. This diet provided neither niacin-rich foods like meats and certain vegetables, nor protein-rich foods containing tryptophan. Pellagra was caused by this lack of niacin intake. Pellagra is uncommon today. This is due to widespread niacin enrichment of most cereals, flours, pastas, and corn meals.

For people who eat enough protein, niacin deficiency is not common. Niacin deficiency symptoms include:

  • weakness
  • loss of appetite
  • digestive upsets
  • insomnia
  • headaches
  • irritability
  • frequently, a sore, swollen, purple-red tongue.
  • More drastic niacin shortfall leads to pellagra, which can result in symptoms such as:

  • skin and gastrointestinal lesions
  • swollen mucous membranes
  • diarrhea
  • dementia
  • death, in extreme cases
  • But, as mentioned above, pellagra is all but a thing of the past in the United States.

    In recent years, niacin has been used with some success to treat people with high cholesterol levels. The high dose required to bring about any change in cholesterol, up to 3,000 mg per day, can bring on side effects. Common side effects include flushing of the skin and itching. High doses of niacin may also cause liver damage or stomach ulcers. Because of these potentially dangerous side effects, niacin should only be used to control cholesterol when prescribed by a doctor.

    The Recommended Dietary Allowance, called the RDA, for niacin is:

  • Adult males, age 19 to 50: 19 milligrams (mg)
  • Adult males, age 50 and older: 15 mg
  • Adult females, age 19 to 50: 15 mg
  • Adult females, age 50 and older: 13 mg
  • Pregnant women: 17 mg
  • Lactating or breastfeeding women: 20 mg


    Next section


    Vitamin B3: Functions and Sources

    Author: Clare Armstrong, MS, RD
    Reviewer: Kathleen A. MacNaughton, RN, BSN
    Date Reviewed: 09/26/02

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