Vitamin B1, also called thiamin, was the first B vitamin discovered. Every cell in your body needs thiamin to make adenosine triphosphate, or ATP, the body's main energy-carrying molecule. The heart, in particular, has considerable need for thiamin in order to keep up its constant work. Severe deficiency of thiamin results in beriberi, a disease common in the 19th century, but rare today. Many of the principal symptoms of beriberi involve impaired heart function.

Requirements/Sources

Your need for vitamin B 1 varies with age. The official US and Canadian recommendations for daily intake are as follows:

  • Infants
    • 0-6 months: 0.2 mg
    • 7-12 months: 0.3 mg
  • Children
    • 1-3 years: 0.5 mg
    • 4-8 years: 0.6 mg
    • 9-13 years: 0.9 mg
  • Males
    • 14 years and older: 1.2 mg
  • Females
    • 14-18 years: 1.0 mg
    • 19 years and older: 1.1 mg 
  • Pregnant or Nursing Women: 1.4 mg

Although vitamin B 1 deficiency is rare in the developed world, it may occur in certain medical conditions, such as alcoholism, anorexia, Crohn's disease, and folate deficiency. People undergoing kidney dialysis or taking loop diuretics may also become deficient in vitamin B 1. Certain foods may impair your body's absorption of B 1 as well, including fish, shrimp, clams, mussels, and the herb horsetail.

Brewer's and nutritional yeast are the richest sources of B 1. Peas, beans, nuts, seeds, and whole grains also provide fairly good amounts.

Therapeutic Dosages

A typical dose of vitamin B1 for therapeutic purposes is 200 mg daily, although much higher dosages have also been tried.

Some nutritional experts recommend taking B 1 with other B vitamins in the form of a B-complex supplement. However, there is no meaningful evidence that this offers any advantage.

Therapeutic Uses

Congestive heart failure (CHF) is a condition in which the pumping ability of the heart declines, and fluid begins to accumulate in the lungs and legs. Standard treatment for CHF includes strong "water pills" called loop diuretics. These drugs, however, deplete the body of B 1.1 Since the heart depends on vitamin B 1 for its proper function, this is potentially quite worrisome. Preliminary evidence, including a small double-blind placebo-controlled trial, hints that supplementation with B 1 can improve symptoms.2,3

One double-blind study suggests that thiamin taken at a dose of 50 mg daily might enhance mental function.14

Other potential uses of thiamin have even less scientific support. Observational studies of people with HIV infection suggest (but definitely do not prove) that increased intake of vitamin B 1 might slow progression to AIDS and enhance overall survival rate.4,5 Weak and contradictory evidence hints that vitamin B 1 may be helpful for Alzheimer's disease.6-10 Vitamin B 1 has also been proposed as a treatment for epilepsy, canker sores, and fibromyalgia, but the evidence for these uses is too preliminary to cite.

Safety Issues

Vitamin B 1 appears to be quite safe even when taken in very high doses.

Interactions You Should Know About

If you are taking: