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.

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.