Foods, benefits, and deficiency symptoms

Vitamin B1 or thiamin is essential for glucose metabolism and nerve, muscle, and heart function. People may need supplements if their diet does not provide enough B vitamins, during hemodialysis, and for other reasons.

Also known as thiamine or thiamin, vitamin B1 is a water-soluble vitamin, as are all vitamins of the B complex. It enables the body to use carbohydrates as energy.

Water-soluble vitamins travel through the bloodstream. If the body does not use the vitamins, it excretes them in urine.

Daily vitamin B1 intake requirements may depend on someone’s age and sex. However, the National Institutes of Health (NIH) suggests adult males typically require 1.2 milligrams (mg), and adult females typically require 1.1 mg.

This article examines foods that contain thiamin, its benefits, signs of a deficiency, side effects, and more.

In the United States, people consume around half of their vitamin B1 intake in foods that naturally contain thiamin, while the rest comes from foods that manufacturers fortify with the vitamin.

The following foods are a source of vitamin B1.


Some sources of protein that contain vitamin B1 include:

Fruits and vegetables

Fruits and vegetables that contain vitamin B1 include:


Grain options that contain vitamin B1 include:

  • the outer layers and germ of cereals
  • whole grains
  • pulses
  • breakfast cereals fortified with vitamin B1
  • products made with enriched white flour or white rice

The NIH notes that one serving of fortified breakfast cereal provides 1.2 mg of thiamin, which meets the daily recommendation of thiamin for most adults.

Unenriched white rice will contain only one-tenth of the thiamin available in brown rice.

One slice of whole wheat bread contains 0.1 mg or 8% of the daily requirement.


Heating, cooking, and processing foods and boiling them in water destroys thiamin. As vitamin B1 is water-soluble, it dissolves into cooking water.

Humans need a continuous supply of vitamin B1 because the body does not store it. It should be part of someone’s daily diet.

Vitamin B1 helps prevent complications in the:

  • nervous system
  • brain
  • muscles
  • heart
  • stomach
  • intestines

It is also involved in the flow of electrolytes into and out of muscle and nerve cells.

A vitamin B1 deficiency can lead to conditions such as beriberi, which involves disorders of the heart, nerves, and digestive system.

Uses in medicine

People who may require thiamin to treat low levels of vitamin B1 include those with peripheral neuropathy, an inflammation of the nerves outside the brain.

People with ulcerative colitis, persistent diarrhea, and poor appetite may also require thiamin. Someone in a coma may require thiamin injections.

Thiamin supplements may also be necessary for people who experience:

People who are pregnant, lactating, or use diuretics may also benefit from vitamin B1 supplements.

A vitamin B1 deficiency commonly leads to beriberi, a condition that features problems with the peripheral nerves and wasting. Other symptoms of beriberi include:

Who is at risk of B1 deficiency?

People at risk of thiamin deficiency include those affected by:

  • pregnancy
  • chronic illness
  • inadequate dietary intake
  • alcoholism
  • bariatric surgery
  • chronic diuretic therapy

Prolonged, untreated thiamin deficiency may lead to Wernicke-Korsakoff syndrome, a disorder that can affect people with chronic alcoholism, gastrointestinal disorders, or AIDS.

People with Wernicke-Korsakoff syndrome and those who are withdrawing from alcohol may receive thiamin injections to help them recover.

Older adults and people with diabetes may also have a higher risk of developing a vitamin B1 deficiency.

All B vitamins are water-soluble. They help to convert carbohydrates, fats, and protein into energy, or glucose.

B vitamins are necessary for keeping the liver, skin, hair, and eyes healthy. They also play a role in the nervous system, and they are necessary for good brain function.

According to the United Kingdom’s National Health Service (NHS), thiamin may cause the following side effects:

Symptoms of an allergy may also occur, including difficulty breathing, facial or throat swelling, confusion or dizziness, and a tight throat. People with these symptoms should seek emergency care.

The U.S. Food and Drug Administration (FDA) also urges people to check with a healthcare professional before using supplements with or as a substitute for foods.

They call on the public to seek a physician’s advice on improving their health rather than self-diagnosing.


The chemotherapy drug fluorouracil (Adrucil) may interact with thiamin. People should speak with a doctor before introducing vitamin B1 supplements into their diet.

Certain foods and drinks may also contain enzymes called thiaminases, which can destroy thiamin. These foods include:

  • tea
  • coffee
  • raw fish
  • shellfish

Below are some common questions about thiamin.

What does vitamin B1 do?

Vitamin B1 supports the nervous system and helps the body turn food into energy. It is important for cell function, growth, and development.

What are the symptoms of low vitamin B1?

A vitamin B1 deficiency may cause the following symptoms:

  • weight loss
  • confusion
  • short-term memory loss
  • an enlarged heart
  • muscle weakness

What foods are high in vitamin B1?

Food sources for thiamin include:

  • cereals fortified with vitamin B1
  • pork
  • fish, including trout, tuna, and mussels
  • black beans
  • whole grains

People require vitamin B1 as a regular part of their diet to support vital bodily functions. A thiamin deficiency may lead to symptoms such as confusion, muscle weakness, and heart problems.

Doctors may recommend thiamin supplements for people who are unable to get adequate amounts through their diet.

People should speak with their doctor if they experience symptoms of a vitamin B1 deficiency.


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