Overview
Thiamine, needed to release energy from carbohydrate. Stores are small — a few weeks at most — so a shortage develops faster than for most vitamins, and it strikes nerves and heart.
Why your body needs it
Converts carbohydrate into energy, and is needed for nerve and heart muscle function.
Food sources
- Pork
- Whole grains and fortified cereals
- Legumes
- Sunflower seeds
- Trout
Destroyed by prolonged heat. Alcohol impairs absorption directly.
Recommended intake
1.2 mg (men) · 1.1 mg (women) for most adults. The upper limit, past which harm becomes likely, is None established.
Reference intakes are population figures. Pregnancy, illness, age and medication all move an individual’s needs, which is one of several reasons this page is information rather than advice.
Deficiency — Beriberi · Wernicke–Korsakoff syndrome
A sustained shortage has a name here: Beriberi · Wernicke–Korsakoff syndrome. That is worth pausing on — nutrients whose deficiency earned a name are the ones where the consequences were severe enough, historically, to be described as a disease.
Most at risk: Heavy alcohol use above all. Also after bariatric surgery, and with prolonged vomiting.
Possible causes
Alcohol dependence is the commonest cause in high-income countries, through poor intake and poor absorption together. Also prolonged vomiting including in pregnancy, bariatric surgery, and diets built on polished rice.
Signs & symptoms
Nerve damage and weakness (dry beriberi) or heart failure and swelling (wet beriberi). In heavy drinkers it causes Wernicke encephalopathy — confusion, unsteadiness and eye movement problems — which is a medical emergency and can become permanent.
Every sign here has other, often likelier, explanations. A list of symptoms is a reason to look into something, never a diagnosis.
Testing / diagnosis
Whole blood thiamine or erythrocyte transketolase activity exists but is not fast. Where Wernicke’s encephalopathy is suspected, treatment is given immediately rather than waiting for a result.
Food strategies
Pork, wholegrains, legumes, nuts, seeds and fortified cereals. Refining removes most of it, and it leaches into cooking water.
Supplements
Water-soluble, poorly stored and not toxic in ordinary amounts. In alcohol dependence, thiamine is given before any glucose, because glucose without it can precipitate acute deficiency.
Safety
No known toxicity — excess is excreted.
Interactions: Loop diuretics increase losses.
When to seek professional advice
Confusion, unsteadiness or abnormal eye movements — particularly with a history of heavy drinking or persistent vomiting — need urgent medical attention, not a supplement. This is one of the few nutritional emergencies.
This page is general reference information, not medical or dietetic advice, and it cannot account for your health history or medications. Decisions about testing, supplements or significant dietary change belong in a conversation with your doctor, pharmacist or a registered dietitian.