Vitamin B1 (Thiamine)

Thiamine, also spelled thiamin and known as vitamin B1, is a water-soluble B vitamin. Inside cells it becomes thiamine diphosphate, says the NIH (the US National Institutes of Health). Enzymes need this helper to turn glucose, amino acids and fats into energy. Deficiency shows up mostly as nerve and heart problems, with beriberi as the classic disease, says EFSA (the EU’s food safety agency).

The body keeps very little. An adult holds about 25 to 30 mg. Its biological half-life, a measure of how fast it is used up, is 9 to 18 days. So thiamine has to come from food all the time.

EFSA notes that deficiency occurs mainly where the diet rests on milled white cereals such as polished rice. The NIH says unenriched white rice has about one tenth of the thiamine of unenriched brown rice. Most people in the US eat enough: national survey data show only 6% have an intake below the average requirement.

Two things most readers do not know. In the US, about half of dietary thiamine comes from foods it is added to, such as bread and cereals, the NIH says. And heavy drinking blocks the carriers that take thiamine up in the gut. That is why alcohol use disorder is the most common cause of deficiency in highly industrialized countries.

This page weighs 25 studies on heart failure, sepsis, alcohol, nerve damage, fortified food and benfotiamine.

Health benefits of thiamine

• ★★★EU-approved thiamine claims, not study resultsThe EU allows foods that are a source of thiamine to claim it supports normal energy metabolism, nervous system function, psychological function and heart function. These are normal roles of the vitamin, not a treatment for any disease.
• ★★No clear heart benefit in heart failureIn 7 trials (274 people with heart failure), thiamine raised the share of blood pumped per beat by 1.7 percentage points, which could be chance. Thiamine corrected deficiency, so the authors say it helps only where deficiency is present.
• ★★No clear cut in deaths from sepsisThiamine by drip did not clearly cut short-term deaths in 9 trials (520 people with sepsis, a life-threatening reaction to infection). A vitamin C, thiamine and steroid mix did not cut days on life support.
• ★★Raised thiamine in mothers and breast milkIn Cambodia, six months of fish sauce with added thiamine raised thiamine in mothers’ blood cells and breast milk. Daily doses of 1.2 mg raised breast milk thiamine about as much as 10 mg.
• ★Best thiamine dose in alcohol misuse unclearOnly one usable trial (107 people) found injected 200 mg a day beat 5 mg for working memory, but not at other doses. Two other trials of injected thiamine found higher doses were not clearly better on thinking tests or nerve function.

Foods high in thiamine

Beans and seeds lead our USDA ranking per serving, against a Daily Value of 1.2 mg (the FDA’s daily target for food labels). Navy beans give 0.43 mg per cup (182 g) and black beans 0.42 mg per cup (172 g). Sunflower seeds give 0.42 mg per ounce (28 g). Peas, hemp seeds and cranberry beans are close behind, as the ranking shows.

Per 100 g, flaxseeds (1.64 mg), sunflower seeds (1.48 mg) and hemp seeds (1.28 mg) lead, then macadamia nuts and pistachios. Per 100 kcal (the same calories of each food), asparagus (0.72 mg) and endive (0.47 mg) top the list, ahead of white mushrooms and spinach.

Pork and fortified grain foods are major sources in Western diets but do not appear in our ranking. The NIH table lists fortified breakfast cereal at 1.2 mg per serving (100% of the Daily Value).

Cooked enriched egg noodles have 0.5 mg per cup. A broiled bone-in pork chop and cooked trout have 0.4 mg each in 3 oz. Boiled black beans have 0.4 mg per half cup and mussels 0.3 mg in 3 oz.

Breads, cereals and infant formulas in the US and many other countries are fortified with thiamine. About half of the thiamine in the US diet comes from added thiamine.

Cooking and refining change what reaches the plate. Thiamine dissolves in water, so a significant amount is lost when cooking water is thrown out. Bread has 20% to 30% less thiamine than its raw ingredients, and pasteurization lowers the small amount in milk by up to 20%. EFSA lists alkaline conditions, high temperatures and sulfites among the causes of significant loss.

Milling matters most for rice: unenriched white rice has one tenth of the thiamine of unenriched brown rice. The NIH counts a half cup of enriched white rice at 0.1 mg, against 0.2 mg for unenriched brown rice.

Some foods work against thiamine. Thiaminases, enzymes in raw or fermented fish, ferns and insects, break it down. Phenolic acids in plants, such as caffeic, chlorogenic and tannic acid, can make it unavailable. Bioavailability (how much the body can absorb) fell in controlled studies comparing diets with and without tea, as EFSA reports.

These factors matter mostly where the diet is already low in thiamine.

How thiamine works

Most of this is biochemistry from test tubes, cells, animals and tissue samples, summarized in reviews, not from trials. Four ideas cover it. Thiamine diphosphate helps energy enzymes, and most of the thiamine sits in the cell’s fluid and mitochondria (the cell’s power plants).

Carriers let it in, and alcohol interferes with them. The body keeps only a small store. Here is each one, and what has been seen in people.

It helps four enzymes release energy

Free thiamine is turned into thiamine diphosphate (TDP, also called thiamine pyrophosphate), the form that works as a coenzyme (an enzyme helper). About 80% of the 25 to 30 mg of thiamine in an adult body is TDP, according to the NIH.

EFSA lists four main jobs. TDP is needed by pyruvate dehydrogenase, which converts pyruvate to acetyl-coenzyme A, and by alpha-ketoglutarate dehydrogenase in the Krebs cycle. It is also needed by an enzyme that breaks down the keto acids from branched-chain amino acids. And it is needed by transketolase in the pentose phosphate pathway, which supplies five-carbon sugars and NADPH.

In the brain, acetyl-coenzyme A and alpha-ketoglutarate also feed the production of the messengers acetylcholine and GABA.

People carry little, and it sits mostly in the cell’s fluid and mitochondria

In a 2010 study of human biopsies (tissue samples), total thiamine was lower in people than in other animals. The authors link our high sensitivity to deficiency to low blood thiamine and low tissue TDP. Levels of TDP also fell with age.

EFSA, summarizing the same data, reports the highest TDP in heart and skin. Inside cells, in most tissues, EFSA gives the split as about 50% in the fluid part and 35% in mitochondria. About 10% is in the nucleus and 5% in the microsomes. The mitochondrial share fits the energy jobs above.

Carriers let it in, and alcohol gets in their way

Gut enzymes free thiamine from its phosphates, and then two carriers, ThTR-1 and ThTR-2, take it up, EFSA explains. Rare gene changes show how much the carriers matter. Mutations in the ThTR-1 gene (SLC19A2) cause thiamine-responsive megaloblastic anemia. This syndrome brings anemia, deafness and diabetes, and it improves with pharmacologic (drug-sized) doses of thiamine.

At low concentrations in the gut, the carriers do most of the work. At high concentrations, simple diffusion adds a second route, and EFSA notes that absorption becomes less efficient above about 5 mg a day.

Alcohol reduces absorption: it inhibits the carrier route and not the diffusion route, according to a review. Chronic alcohol feeding cut ThTR-1 levels in rats and carrier uptake in human gut cells. In 20 people with chronic alcohol dependence, 21% of a labeled thiamine dose was found in stool, against 4% in 10 healthy people. EFSA reports this from an older study.

The body keeps only a small store

An adult body holds about 25 to 30 mg of thiamine, mostly in muscle, heart, brain, liver and kidneys. The liver stores only a very small amount, the NIH says, and EFSA gives the biological half-life as 9 to 18 days.

More than 80% of the thiamine in blood is inside red blood cells, so a plasma test can mislead. The NIH says blood levels are not reliable indicators of status. Status is often measured indirectly, through transketolase (an enzyme) activity with and without added TDP.

Needs also track energy use. In a depletion study EFSA describes, 0.84 mg a day failed to restore normal enzyme activity in people eating 3,600 kcal a day. It did restore it in those eating 2,800 kcal.

What has been seen in people

The biochemistry fits the deficiency diseases but not always the supplement claims. Where thiamine is truly low, treatment works, and fortified food raised thiamine in Cambodian women and breast milk.

Where it is not low, extra thiamine did little in heart failure, sepsis and diabetic nerve damage. The exceptions are small positive trials, such as the one in bowel disease fatigue. Heavy drinking, bariatric surgery and some medicines are where the carrier and storage story turns into real risk. The studies above and the deficiency section below show this.

How much thiamine do you need?

Adult men need 1.2 mg of thiamine a day and adult women 1.1 mg. That is the US recommended dietary allowance (RDA), an amount that covers nearly all healthy people. The label value, the Daily Value, is 1.2 mg.

In the EU, EFSA sets the population reference intake at 0.1 mg per megajoule (MJ) of energy eaten, or 0.4 mg per 1,000 kcal. That is because thiamine needs rise with energy use. For adults it works out to about 0.7 to 1.4 mg a day, depending on age, sex and activity level.

In the US, teenagers aged 14 to 18 need 1.2 mg (boys) or 1.0 mg (girls) a day. Children aged 9 to 13 need 0.9 mg. Pregnancy and breastfeeding raise the US allowance to 1.4 mg a day.

EFSA adds 0.03, 0.11 and 0.21 mg a day in the three trimesters, to match the extra energy needed. It adds 0.21 mg a day while breastfeeding.

For infants, the US sets an adequate intake (AI, a best-estimate amount) of 0.2 mg a day up to 6 months. From 7 to 12 months it is 0.3 mg.

For older adults, the US allowance stays at 1.2 and 1.1 mg from age 51. EFSA’s values in mg a day are lower because older adults eat less. At ages 60 to 69, they run from 0.69 to 1.22 mg across activity levels.

People who drink heavily, have had bariatric surgery or take loop diuretics are at higher risk of low status, as the next part shows.

Thiamine deficiency: signs and who is at risk

Early deficiency causes weight loss, loss of appetite, confusion, short-term memory loss and muscle weakness, according to the NIH. It can also cause heart symptoms such as an enlarged heart. EFSA adds nerve inflammation, swelling, extreme fatigue, irritability, forgetfulness, poor coordination, constipation and labored breathing.

The best-known disease is beriberi. Dry beriberi is mainly a nerve disorder, with sensory and motor peripheral neuropathy (damage to nerves outside the brain and spinal cord). Wet beriberi adds heart failure, an enlarged heart and a fast heart rate, and a rapidly developing form is called Shoshin beriberi. Infantile beriberi can appear in breastfed infants of thiamine-deficient mothers at 2 to 6 months of age.

Wernicke’s encephalopathy brings eye movement problems, poor balance and confusion. Autopsy studies show it is greatly underdiagnosed, and the NIH says up to 20% of people with it die without treatment. Those who survive without treatment develop Korsakoff’s psychosis, with severe memory loss, disorientation and confabulation (making up memories without meaning to).

Suspected Wernicke’s encephalopathy is a medical emergency. The European neurology guideline advises 200 mg of thiamine three times a day, preferably into a vein and before any glucose.

The NIH names the groups most at risk. In highly industrialized countries, alcohol use disorder is the most common cause. Up to 80% of people with chronic alcoholism develop deficiency, because alcohol reduces absorption, liver stores and activation of thiamine.

Older adults are another group: 20% to 30% have lab signs of some deficiency. The NIH lists poor intake, many medicines and lower absorption. People with HIV, diabetes and heart failure also show low status in studies, though how much it matters is unclear.

Across studies, 17% to 79% of people with diabetes had poor status by an enzyme test. For heart failure, the range was 21% to 98%.

The loop diuretic furosemide and the chemotherapy drug fluorouracil can lower thiamine or its action. After bariatric surgery, the pooled rate of deficiency was 19% at 3 months in one meta-analysis. The European guideline recommends following thiamine status for at least 6 months.

In pregnancy, severe vomiting (hyperemesis gravidarum) can deplete thiamine between 10 and 15 weeks. A review of 177 case reports found that Wernicke’s encephalopathy in this setting often went untreated or was treated with too little thiamine.

EFSA also names diets rich in thiaminase, an enzyme found in some raw or fermented fish, ferns and insects. Critically ill patients given glucose drips without thiamine are another group, a clinical review says.

Testing is not simple. Blood thiamine is a poor guide, so clinics use the red cell transketolase test. According to the NIH, a TDP effect of 0% to 15% is normal, 15% to 25% marginal and above 25% deficient. Urinary thiamine under 100 mcg (micrograms) a day suggests too little intake.

For mild deficiency, the WHO (World Health Organization) advises 10 mg by mouth daily for a week. After that comes 3 to 5 mg for at least 6 weeks. Severe cases need injections, the NIH reports.

Recovery depends on the stage. Supplemental thiamine, often by injection, quickly cures beriberi. At the Korsakoff stage, though, injected thiamine does not lead to recovery in about one quarter of patients.

Forms of thiamine: absorption and effects

Thiamine supplements differ in the molecule, in how well the gut takes it up and in how it is used. Thiamine hydrochloride and thiamine mononitrate are the common forms in supplements and in fortified food. The NIH calls them stable and water soluble, and EFSA says both may be added to foods and supplements in the EU.

EFSA adds that thiamine monophosphate chloride and thiamine pyrophosphate chloride may be added to supplements. Benfotiamine is a synthetic derivative that is not water soluble and is converted to thiamine in the body. Sulbutiamine, fursultiamine and thiamine disulfide are other fat-soluble forms sold or studied for fatigue and nerve symptoms.

The honest bottom line: the studies we found compare blood levels, not health. Benfotiamine reached much higher blood levels than thiamine hydrochloride in healthy volunteers. But in long trials in diabetes, the higher levels did not improve nerve measures.

We found no head-to-head human study of the hydrochloride against the mononitrate. We found none showing that sulbutiamine works better than thiamine, and none on the phosphate forms. For correcting or preventing deficiency, the guidelines and trials used plain thiamine, often by injection.

In the outcome trials above, the sepsis trials used thiamine by injection (VICTAS gave it with vitamin C and hydrocortisone, a mixture). The kidney trial used thiamine 300 mg a day by mouth. The neuropathy, kidney and Alzheimer’s trials used benfotiamine at 300 to 900 mg a day. A pilot trial in older adults with heart failure used thiamine mononitrate 500 mg a day. Its gains in ejection fraction and NT-proBNP were not statistically significant.

Form	Activity or conversion	What studies show	Source
Thiamine hydrochloride	Not stated. The NIH calls it stable and water soluble	The reference form in the benfotiamine comparison, with much lower plasma thiamine than benfotiamine. EFSA lists it as allowed in foods and supplements. We found no human study comparing it head to head with the mononitrate.	1, 2, 3
Thiamine mononitrate	Not stated. The NIH calls it stable and water soluble	The other common supplement and fortification form. At 500 mg a day for 90 days in 24 older adults with heart failure it was well tolerated, with nonsignificant gains in ejection fraction and NT-proBNP.	1, 2, 4
Benfotiamine	Converted to thiamine in the body (NIH). Relative bioavailability against thiamine hydrochloride: 1,147% for plasma thiamine and 196% for red cell thiamine diphosphate	Raised blood levels more and sooner than fursultiamine and thiamine disulfide in 7 volunteers. In outcome trials, a 6-week trial found borderline symptom gains, and 12-month and 24-month trials found no change in nerve measures despite higher blood levels.	1, 3, 5, 6, 7, 8
Sulbutiamine	Not stated	A fat-soluble form that, according to the authors of one study, crosses the blood-brain barrier more readily than thiamine. In an uncontrolled study of 26 people with multiple sclerosis, 400 mg a day for 2 months went with lower fatigue scores. We found no placebo-controlled trial of it for fatigue.	9
Fursultiamine and thiamine disulfide	Not stated	Gave less thiamine than benfotiamine in 7 volunteers; thiamine disulfide gave the least.	5
Thiamine monophosphate and pyrophosphate chloride	Not stated	EFSA says they may be added to food supplements in the EU. We found no human study of how well they are absorbed.	2
Thiamine in food	Phosphates in animal foods, free thiamine in plants (EFSA)	Gut enzymes remove the phosphates before uptake. In healthy people more than 95% of intakes under 2 mg a day were absorbed. Alcohol, sulfites, thiaminases and some plant phenols lower availability.	2

Here are the head-to-head studies of forms, 2 in all.

Is thiamine safe? Supplements, dose and interactions

Thiamine from food is not a safety concern, and neither the US nor the EU has set an upper level. The US Food and Nutrition Board set no tolerable upper intake level (UL). It found no reports of adverse effects from intakes of 50 mg a day or more from food or supplements. It suggested that absorption falls sharply above 5 mg, and the body excretes the excess in urine.

EFSA reports that the EU Scientific Committee on Food reached the same conclusion in 2001. Data on harm from oral thiamine were limited, absorption declines above 5 mg a day, and no upper level could be set. No upper level means no proven safe ceiling either, and the Board noted that excessive intakes could in principle cause harm.

• Doses used in trials. The inflammatory bowel disease trial gave 600 to 1,800 mg a day by mouth for 4 weeks and saw only mild side effects. A 12-month trial gave benfotiamine 600 mg a day, well tolerated. Your supplement is probably far lower; multivitamins typically hold about 1.5 mg, the NIH says.
• Injections. In a US emergency department study, 12 of 989 patients (1.1%) had a reaction to a 100 mg intravenous dose, mostly short local irritation. A chart review of 8,606 doses in 2,595 patients found no anaphylaxis (a severe allergic reaction). Still, anaphylaxis with cardiac arrest has been reported after an infusion in one man. That is why injections are given where it can be treated. The European guideline rates the overall safety of thiamine as very good.
• Drug interactions. The NIH says thiamine is not known to interact with medicines, but some medicines lower thiamine. Furosemide (Lasix) increases urinary loss. Fluorouracil chemotherapy has been linked to cases of beriberi or Wernicke’s encephalopathy, possibly because it blocks the formation of TDP. Whether supplements prevent this in people on loop diuretics has not been settled in trials.
• Who should ask a doctor. Seek care rather than self-treat if you drink heavily, have had bariatric surgery or have long-lasting vomiting (including in pregnancy). The same goes if you take loop diuretics or fluorouracil, or have confusion, poor balance, eye movement changes or burning, tingling feet. Suspected Wernicke’s encephalopathy is an emergency and needs injected doses.

How to get more thiamine

• Eat beans, seeds and whole or enriched grains. In our ranking, a cup of navy beans gives 0.43 mg (36% of the Daily Value) and an ounce of sunflower seeds 0.42 mg. The NIH adds pork, trout and fortified cereals.
• Keep the cooking water and choose less refined grains. Thiamine dissolves in water, so use the liquid from beans or vegetables in soups. Unenriched white rice has one tenth of the thiamine of unenriched brown rice.
• Do not self-treat risk situations. If you drink heavily or have had bariatric surgery, ask for a status check. Guidelines advise following thiamine status for at least 6 months after surgery. A multivitamin at about 1.5 mg is not a treatment for deficiency.

History of thiamine

For centuries, beriberi was blamed on miasmas (bad air) rising from wet soil, and later on an unknown infectious organism. In 1884, the Japanese Navy doctor Takaki Kanehiro took white rice out of sailors’ diets and added more varied food. Beriberi disappeared during a voyage of several months. He credited the protein, the diet was costly, and the idea was soon forgotten.

In the Dutch East Indies, Christiaan Eijkman noticed that chickens fed polished rice developed a paralysis like beriberi. Chickens fed unpolished brown rice did not. His successor Gerrit Grijns concluded correctly that foods contain unknown substances needed by the peripheral nervous system.

A 2019 biography of Eijkman describes a large survey of Java prisons. Beriberi struck 9 of about 95,000 prisoners fed unpolished rice, and 4,200 of about 150,000 fed polished rice.

In 1926, Barend Jansen and Willem Donath isolated and crystallized a substance that cured polyneuritis (nerve inflammation) in pigeons. Robert Williams synthesized thiamine in 1936. Casimir Funk proposed in 1912 that such substances are essential to life and named them vitamines. Eijkman received the 1929 Nobel Prize in medicine “for his discovery of the antineuritic vitamin”.

Frequently asked questions about thiamine

Why is thiamine given to people who drink heavily?

Heavy drinking lowers thiamine intake and also blocks its absorption. In a study EFSA cites, 21% of a labeled dose ended up in stool in 20 people with chronic alcohol dependence. In 10 healthy people it was 4%. The NIH says up to 80% of people with chronic alcoholism develop thiamine deficiency. For suspected Wernicke’s encephalopathy, the European guideline advises 200 mg of thiamine three times a day, preferably into a vein and before any glucose. A Cochrane review found too few trials to say which dose is best, so this is a clinician’s decision, not self-care.

How long does it take to recover from vitamin B1 deficiency?

It depends on the stage. The NIH says supplemental thiamine, often by injection, quickly cures beriberi. Wernicke’s encephalopathy is an emergency, and without treatment up to 20% of people with it die. At the later Korsakoff stage, injected thiamine does not lead to recovery in about one quarter of patients. For mild deficiency, the WHO advises 10 mg by mouth daily for a week. After that comes 3 to 5 mg a day for at least 6 weeks.

Which foods are highest in thiamine?

Beans and seeds lead our USDA ranking per serving, against a Daily Value of 1.2 mg. Navy beans give 0.43 mg per cup, black beans 0.42 mg, sunflower seeds 0.42 mg per ounce and peas 0.41 mg. Per 100 g, flaxseeds (1.64 mg), sunflower seeds (1.48 mg) and hemp seeds (1.28 mg) lead. The NIH adds fortified breakfast cereal at 1.2 mg per serving and enriched egg noodles at 0.5 mg per cup. A broiled pork chop has 0.4 mg.

Does cooking destroy thiamine?

Partly. Thiamine dissolves in water, so a significant amount is lost when cooking water is thrown out. Bread has 20% to 30% less thiamine than its raw ingredients, according to the NIH. Pasteurization lowers the small amount in milk by up to 20%. EFSA lists alkaline conditions, high temperatures and sulfites as causes of significant loss. So using the cooking liquid in soups and sauces keeps more of what dissolved.

Is benfotiamine better than thiamine?

It raises blood levels more, but that has not meant better health so far. In healthy volunteers, benfotiamine gave about 11 times more thiamine in plasma than thiamine hydrochloride, and about twice the thiamine diphosphate in red cells. Yet a 12-month trial in type 2 diabetes and a 24-month trial in type 1 diabetes found no change in nerve measures. A 6-week trial found a borderline gain in symptom scores. Food or ordinary thiamine covers normal needs.

Can you take too much thiamine?

Neither the US nor the EU has set an upper level, because no harm has been reported from high intakes of food or supplements. The NIH cites intakes of 50 mg a day or more. Absorption also falls above about 5 mg a day, and the body excretes the excess in urine. A trial of 600 to 1,800 mg a day for 4 weeks saw only mild side effects. Injections are different: 12 of 989 patients (1.1%) had a reaction to a 100 mg intravenous dose, mostly local irritation. Anaphylaxis has been reported in a case report.

Does thiamine repel mosquitoes?

There is no good evidence that it does. In a test with human volunteers and Anopheles stephensi mosquitoes, vitamin B supplementation had no effect on how attractive skin odors were. The authors note that earlier small studies also found vitamin B complex ineffective as a repellent. The idea is common on the web.

Does vitamin B1 give you energy?

Thiamine is needed to turn food into energy, and the EU authorizes the claim that it contributes to normal energy-yielding metabolism. But that describes a normal role, not extra energy. In a trial of 80 elderly Irish women with marginal deficiency, 10 mg a day reduced fatigue. In another, 40 people with bowel disease and severe fatigue improved on 600 to 1,800 mg. In people with normal status the evidence is thin, such as one study of 16 male athletes taking 100 mg a day.