March 21, 2017


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 B vitamins, thiamin (or vitamin B-1) is best known for its role in making energy. Beriberi is the most common disease linked with thiamin deficiency. But it isn’t common in the U.S.

Thiamin is needed for carbohydrates to break down. It helps convert glucose and carbohydrates into energy. It works as a coenzyme in more than 20 metabolic processes.

Thiamin is also needed for the nervous system and the brain to work well. Because thiamin is needed for nerve conduction, deficiency can lead to nerve problems.

Medically valid uses

Thiamin is used to treat or prevent beriberi. It’s also Wernicke-Korsakoff syndrome (WKS). This is a severe thiamin deficiency that’s common in people with alcoholism. It’s 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 studies.

Thiamin may repel mosquitoes. It may also blood sugar metabolism. It may also aid in improving mental stability. It’s also been used to boost appetite. It may also treat rare metabolic issues related to learning disabilities.

Recommended intake

How much thiamin you need depends on how many calories from carbohydrates you get in your diet. The more carbohydrates you eat, the greater the demand for thiamin. Adults need about 0.4–0.5 mg for every 1,000 calories they eat.

Thiamin is measured in milligrams. The RDA is the Recommended Dietary Allowance.



Infants (0–6 months)

0.2 mg*

Infants (7 months to 1 year)

0.3 mg*

Children (1–3 years)

0.5 mg

Children (4–8 years)

0.6 mg

Children (9–13 years)

0.9 mg

Males (14 years and older)

1.2 mg

Females (14–18 years)

1.0 mg

Females (19 years and older)

1.1 mg

Pregnant women

1.4 mg

Breastfeeding women

1.4 mg

*Adequate Intake (AI). This is based on the average intake in healthy, breastfed infants.

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 10–25%. Thiamin dissolves in water. So, if you cook foods high in thiamin in water and then discard the water, you won’t get as much thiamin.

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

Thiamin is sensitive to light. Store foods with thiamin in light-resistant containers.

Alcoholism and heavy alcohol consumption are two reasons why people need more thiamin. People who eat diets high in refined carbohydrates may also need thiamin supplements. Breastfed infants whose mothers have a poor diet may also need supplements. Thiamin deficiency is often linked with other signs of malnutrition.


People with hyperthyroidism and hypermetabolic states (such as pheochromocytoma) may also need more thiamin. You may also need supplements during times of stress and heavy physical activity.

Women who are pregnant or breastfeeding may need to take supplements. But you should talk to your healthcare provider before doing so.  

Early symptoms of thiamin deficiency include the following:

  • Loss of appetite

  • Weakness

  • Fatigue

  • Nausea

  • Vomiting

Later symptoms may include:

  • Pain

  • Numbness

  • Tingling

  • Muscle weakness

  • Poor coordination

  • Mood swings

  • Irritability

  • Depression

  • Memory loss

The later stages of thiamin deficiency can turn into beriberi. This includes 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 or exudative beriberi include swelling and edema. They also include trouble breathing, enlarged heart, right-side heart failure, and even sudden death.

Symptoms of Wernicke's syndrome include loss of memory, lying, and hallucinations. If left untreated, the issue can progress into a coma and death. In the U.S., this problem is commonly linked with alcoholism. If the damage from WKS isn’t too severe, it can often be quickly reversed with thiamin.

Side effects, toxicity, and interactions

There are no known side effects of too much thiamin. Extra thiamin comes out in the urine.

You shouldn’t take thiamin if you’re allergic to it.

There are no known food or drug interactions with thiamin.


March 21, 2017

Reviewed By:  

Wilkins, Joanna, R.D., C.D.