Nutrition

Vitamin B1 (Thiamin)

Tim

— 2 min read

Vitamin B1, also known as thiamin, is a water-soluble micronutrient. As one of the eight B vitamins, thiamin plays an important role in energy metabolism and cognitive health. Let's look at what it does, and where you can get it from, in a bit more detail:

What does the body use it for?

Thiamin is integral to several key metabolic processes:

  • Energy production: It helps convert carbohydrates into energy by acting as a coenzyme in the production of ATP (adenosine triphosphate), the body's main energy currency.
  • Nervous system function: Thiamin is essential for nerve signal transmission and maintaining proper brain function.
  • Muscle contraction: It supports healthy muscle function, including the heart muscle.
  • Carbohydrate metabolism: Thiamin plays a critical role in breaking down sugars and starches.
  • Antioxidant activity: Free thiamin also helps protect cells from oxidative stress.

Where does it come from?

Plant-based sources

Thiamin is present in many different plant sources:

  • Whole grains (brown rice, oatmeal)
  • Legumes (lentils, black beans, green peas)
  • Nuts and seeds (flax seeds, sunflower seeds, macadamia nuts)
  • Asparagus
  • Acorn squash

Animal-based sources

If you consume animal products, you can get thiamin from:

  • Pork (especially lean cuts)
  • Fish (salmon, tuna, trout)
  • Mussels
  • Liver (beef, lamb)
  • Milk

How much of it should you get?

The recommended daily allowance (RDA) for thiamin varies by age and gender:

  • Adult men: 1.2mg per day
  • Adult women: 1.1mg per day
  • Pregnant women: 1.4mg per day
  • Breastfeeding women: 1.4mg per day
  • Children (1-13 years): 0.5-0.9mg per day
  • Teenagers (14-18 years): 1.0-1.2mg per day

Upper limit for daily intake

Unlike some vitamins, there is no established upper intake level (UL) for thiamin. This is because excess thiamin is generally excreted in urine due to its water-soluble nature. No adverse effects have been consistently reported from high thiamin intake from food or supplements.

What happens if you get too little or too much?

Symptoms of deficiency

Thiamin deficiency, also known as beriberi, can manifest in multiple ways:

Early Symptoms

  • Fatigue and irritability
  • Muscle weakness
  • Tingling or numbness in extremities
  • Loss of appetite
  • Sleep disturbances

Advanced Deficiency

  • Wernicke-Korsakoff syndrome (a brain disorder affecting memory)
  • Confusion and disorientation
  • Heart complications (rapid heartbeat)
  • Muscle atrophy
  • Edema (swelling)

Those at highest risk of thiamin deficiency include people with alcoholism (*), older adults, those with gastrointestinal disorders that affect absorption, and individuals following highly restrictive diets.

(*) The liver uses extra B1 to detoxify alcohol which makes B1 less available for its regular metabolic functions.

Symptoms of excess consumption

As a water-soluble vitamin, excess thiamin is typically excreted through urine. This makes toxicity rare, even with supplementation. However, extremely high doses from supplements may occasionally cause:

  • Nausea
  • Upset stomach
  • Skin irritations
  • Restlessness
  • Allergic reactions (rare)

In practice

Vitamin B1 (thiamin) is essential for energy production, neurological function, and overall cellular health. In general, it is possible to meet your thiamin requirements through a balanced diet including the plant and/or animal-based sources listed above.

While deficiency is uncommon in developed countries, certain populations remain at risk. If you suspect a deficiency, consult a healthcare provider before starting supplementation.

Lastly, proper food preparation is important, as thiamin can be destroyed by heat. Gentle cooking methods can help preserve this vitamin in the foods that you eat.

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