Other name(s):

vitamin B-1, thiamin (U.S. spelling), thiamine (European spelling)

General description

Thiamin is a member of the B family of vitamins (B Complex). It was the first water-soluble vitamin discovered. Like all the B vitamins, thiamin (or vitamin B-1) is best known for its role in the production of energy. Although rare in the United States, beriberi is the most common disease associated with thiamin deficiency.

Thiamin is essential for the breakdown of carbohydrates and helps convert glucose and carbohydrates into energy. It functions as a coenzyme in more than 20 important metabolic processes.

Thiamin is also essential for the normal functioning of the nervous system and the brain. Because thiamin is essential for nerve conduction, thiamin deficiency can lead to nerve problems.

Medically valid uses

Thiamin is used to treat or prevent beriberi (thiamin deficiency), which is rare in the United States, and also Wernicke-Korsakoff syndrome (WKS), a severe thiamin deficiency common among alcoholics and caused by a decreased intake of and ability to use thiamin.

Unsubstantiated claims

Please note that this section reports on claims that have NOT yet been substantiated through scientific studies.

Thiamin is claimed to repel mosquitoes, improve blood sugar metabolism, and aid in improving mental stability. It has also been used to improve appetite, and to alleviate some rare inborn metabolic defects related to learning disabilities.

Again, the above claims are NOT supported in current research findings.

Recommended intake

Thiamin requirements are dependent on the number of calories obtained from carbohydrates in the diet. The higher the carbohydrate content in the diet, the greater the demand for thiamin. Adults require about 0.4 to 0.5 mg for every 1,000 calories consumed.

As indicated below, thiamin is measured in milligrams. It is not currently supplied in International Units (IU). The RDA is the Recommended Dietary Allowance.



Infants (0 to 6 months)

0.3 mg

Infants (6 months to 1 year)

0.4 mg

Children (1 to 3 years)

0.7 mg

Children (4 to 6 years)

0.9 mg

Children (7 to 10 years)

1.0 mg

Boys (11 to 14 years)

1.3 mg

Men (15 to 50 years)

1.5 mg

Women (11 to 50 years)

1.1 mg

Men (51+ years)

1.2 mg

Women (51+ years)

1.0 mg

Pregnant women

1.5 mg

Breastfeeding women

1.6 mg

Food source

Nutrient content per 100 grams

Dried yeast

15.6 mg

Pine nuts

1.28 mg


1.14 mg


1.1 mg

Brazil nuts

1.0 mg


0.86 mg


0.67 mg

Kidney beans

0.6 mg


0.5 mg


0.47 mg

Because thiamin is not stable at high temperatures, cooking reduces its amount in food by 10 to 25 percent. Thiamin levels in food are decreased when the water the food is cooked in is discarded. (This is because much of the thiamin has dissolved in the water.)

Using sulfur dioxide to preserve dried fruit will destroy the thiamin content.

Because thiamin is sensitive to light, foods containing thiamin should be stored in light-resistant containers.

Alcoholism and excessive alcohol consumption are probably the leading reasons for increased need for thiamin. Thiamin supplements are also required to supplement poor diets made up of highly refined carbohydrates, or for infants of breastfeeding mothers who have a poor diet. Thiamin deficiency is often associated with other signs of malnutrition.

Increased amounts of thiamin are needed for those with hyperthyroidism, hypermetabolic states (such as pheochromocytoma), extended periods of stress, and heavy physical activity.

Women who are pregnant or breastfeeding may need to take vitamin supplements, but must consult a physician before doing so.

Early symptoms of thiamin deficiency include anorexia, weakness, fatigue, nausea, and vomiting. These symptoms slowly progress to include increased pain sensation, numbness, tingling, muscle weakness, and poor coordination. At very advanced stages of deficiency, symptoms may include mood swings, irritability, depression, and memory loss.

The later stages of thiamin deficiency can turn into the condition called beriberi, which can take several forms: dry beriberi, wet beriberi, and Wernicke's syndrome.

"Dry" beriberi is associated with stomach and intestinal problems, peripheral nerve changes (polyneuritis), changes in mental state, and loss of muscle mass (atrophy).

Symptoms of "wet beriberi" or "exudative" beriberi include swelling and edema with associated breathing difficulties, enlargement of the heart, and right-side heart failure. Sudden death is not uncommon.

Wernicke's syndrome (sometimes also Wernicke-Korsakoff syndrome) is manifested by cerebral changes that include loss of memory, lying, and hallucinations. If left untreated, the condition can progress into a coma and death. In the United States, this condition is most commonly associated with chronic alcoholism. If the damage from WKS is not too severe and too longstanding, the condition can be quickly reversed by administering thiamin.

Side effects, toxicity, and interactions

There are no known side effects of too much thiamin. Excess thiamin is excreted in the urine.

Do not take thiamin if you are allergic to it.

There are no known significant food or drug interactions.

Additional information

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