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You are here : 3-RX.com > Medical Encyclopedia > Diet and Nutrition > Vitamin B1
      Category : Health Centers > Food, Nutrition, and Metabolism

Vitamin B1

Alternate Names : Thiamine

Overview & Description | Functions and Sources

Thiamine, also known as Vitamin B1, is a water-soluble vitamin. It was the first vitamin to be discovered. Thiamine is one of eight members of the vitamin B complex. The complex also includes:

  • vitamin B2
  • niacin
  • vitamin B6
  • vitamin B12
  • folate
  • biotin
  • pantothenic acid
  • Because thiamine is water-soluble, any extra is passed out of the body in the urine. Thiamine is needed each day to maintain health.


    Daily needs for thiamine are based on the amount of calories taken in each day. The recommended daily allowances, called RDAs, for thiamine are based on 0.5 milligram (mg) for every 1,000 calories consumed. Based on the recommended calorie intake for men and women at certain age levels, the RDAs for thiamine are:

  • men from 15 to 50 years = 1.5 mg
  • men over 50 years = 1.2 mg
  • women from 11 to 50 years = 1.1 mg
  • women over 50 years = 1.0 mg
  • pregnant women = 1.5 mg
  • breastfeeding women = 1.6 mg
  • Thiamine is common in foods. A balanced diet based on the Food Guide Pyramid should provide enough thiamine daily.

    A disease called beriberi, which affects the nerves and heart, is caused by a lack of thiamine in the diet. This is extremely rare in the United States, because enriched grain products are so common. Before grains were enriched, it was much more common.

    Mild thiamine deficiencies are more common. Exceptions may be found with chronic alcoholism, fasting, the elderly, and chronic dieting. Symptoms usually show up in the nerves, stomach, and heart. Early warning signs include:

  • fatigue and weakness
  • loss of appetite and weight loss
  • stomach upset and nausea
  • confusion and irritability
  • depression
  • poor memory
  • sleep disturbances
  • chest pain
  • irritation
  • abdominal discomfort
  • constipation
  • If deficiency continues, symptoms can get worse, and some damage can be permanent. This can include damage to the heart, and changes to the nervous system.

    There is little chance of getting too much thiamine, even when it is taken at high doses. Because it is water soluble and not stored in the body, it is not likely to build up to toxic levels. In older people with low levels of thiamine, taking vitamin B1 pills has improved their lives by decreasing both blood pressure and weight.

    In isolated cases, however, thiamine toxicity has occurred from injections or concentrated formulas used with hospital patients. Toxicity symptoms include nervous irritability, headaches, insomnia, and a rapid pulse.


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    Vitamin B1: Functions and Sources

    Author: Kimberly Tessmer, RD, LD
    Reviewer: Kathleen A. MacNaughton, RN, BSN
    Date Reviewed: 09/26/02

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