Thiamine

Natural Medicines Comprehensive Database rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.

The effectiveness ratings for THIAMINE (VITAMIN B1) are as follows:

Effective for…

• Metabolic disorders. Taking thiamine by mouth helps correct metabolic disorders associated with genetic diseases, including Leigh’s disease, maple syrup urine disease, and others.
• Thiamine deficiency. Taking thiamine by mouth helps prevent and treat thiamine deficiency.
• Brain disorder due to thiamine deficiency (Wernicke-Korsakoff syndrome). Thiamine helps decrease the risk and symptoms of a specific brain disorder called Wernicke-Korsakoff syndrome (WKS). This brain disorder is related to low levels of thiamine (thiamine deficiency) and is often seen in alcoholics. Between 30% and 80% of alcoholics are believed to have thiamine deficiency. Giving thiamine shots seems to help decrease the risk of developing WKS and decrease symptoms of WKS during alcohol withdrawal.

Possibly effective for…

• Cataracts. High thiamine intake as part of the diet is associated with a reduced risk of developing cataracts.
• Kidney disease in people with diabetes. Early research shows that taking high-dose thiamine (100 mg three times daily) for 3 months decreases the amount of albumin in the urine in people with type 2 diabetes. Albumin in the urine is an indication of kidney damage.
• Painful menstruation (dysmenorrhea). Early research suggests that taking thiamine for 90 days stops pain associated with menstruation in girls 12-21 years-old.

Possibly ineffective for…

• Repelling mosquitos. Some research shows that taking B vitamins, including thiamine, does not help repel mosquitos.

Insufficient evidence to rate effectiveness for…

• Athletic performance. Some research suggests that taking thiamine together with pantethine and pantothenic acid (vitamin B5) does not improve muscle strength or endurance in athletes.
• Preventing cervical cancer. Some research suggests that increasing intake of thiamine from dietary and supplement sources, along with other folic acid, riboflavin, and vitamin B12, might decrease the risk of precancerous spots on the cervix.
• Poor appetite.
• Ulcerative colitis.
• Chronic diarrhea.
• Stomach problems.
• Brain conditions.
• AIDS.
• Heart disease.
• Alcoholism.
• Stress.
• Aging.
• Canker sores.
• Other conditions.

More evidence is needed to rate thiamine for these uses.

Thiamine is required by our bodies to properly use carbohydrates.

Thiamine is LIKELY SAFE when taken by mouth in appropriate amounts, although rare allergic reactions and skin irritation have occurred. It is also LIKELY SAFE when given appropriately intravenously (by IV) by a healthcare provider. Thiamine shots are an FDA-approved prescription product.

Thiamine might not properly enter the body in some people who have liver problems, drink a lot of alcohol, or have other conditions.

Special Precautions & Warnings:

Pregnancy and breast-feeding: Thiamine is LIKELY SAFE for pregnant or breast-feeding women when taken in the recommended amount of 1.4 mg daily. Not enough is known about the safety of using larger amounts during pregnancy or breast-feeding.

Furosemide (Lasix) is a loop diuretic used to treat edema and hypertension by increasing urinary output. Research has linked the use of furosemide to decreases in thiamin concentrations, possibly to deficient levels, as a result of urinary thiamin loss. Whether thiamin supplements are effective for preventing thiamin deficiency in patients taking loop diuretics needs to be determined in clinical studies.

• Chemotherapy with fluorouracil

Fluorouracil (also known as 5-fluorouracil; Adrucil) is a chemotherapy drug that is commonly used to treat colorectal and other solid cancers. The published literature includes several cases of beriberi or Wernicke’s encephalopathy resulting from treatment with this drug, possibly because the drug might increase thiamin metabolism and block the formation of TDP, the active form of thiamin. Thiamin supplements might reverse some of these effects.

Areca

Areca (betel) nuts change thiamine chemically so it doesn’t work as well. Regular, long-term chewing of betel nuts may contribute to thiamine deficiency.

Horsetail

Horsetail (Equisetum) contains a chemical that can destroy thiamine in the stomach, possibly leading to thiamine deficiency. The Canadian government requires that equisetum-containing products be certified free of this chemical. Stay on the safe side, and don’t use horsetail if you are at risk for thiamine deficiency.

Coffee and tea

Chemicals in coffee and tea called tannins can react with thiamine, converting it to a form that is difficult for the body to take in. This could lead to thiamine deficiency. Interestingly, thiamine deficiency has been found in a group of people in rural Thailand who drink large amounts of tea (>1 liter per day) or chew fermented tea leaves long-term. However, this effect hasn’t been found in Western populations, despite regular tea use. Researchers think the interaction between coffee and tea and thiamine may not be important unless the diet is low in thiamine or vitamin C. Vitamin C seems to prevent the interaction between thiamine and the tannins in coffee and tea.

Seafood

Raw freshwater fish and shellfish contain chemicals that destroy thiamine. Eating a lot of raw fish or shellfish can contribute to thiamine deficiency. However, cooked fish and seafood are OK. They don’t have any effect on thiamine, since cooking destroys the chemicals that harm thiamine.

• Aneurine Hydrochloride,
• Antiberiberi Factor,
• Antiberiberi Vitamin,
• Antineuritic Factor,
• Antineuritic Vitamin,
• B Complex Vitamin,
• Chlorhydrate de Thiamine,
• Chlorure de Thiamine,
• Complexe de Vitamine B,
• Facteur Anti-béribéri,
• Facteur Antineuritique,
• Hydrochlorure de Thiamine,
• Mononitrate de Thiamine,
• Nitrate de Thiamine,
• Thiamine Chloride,
• Thiamine HCl,
• Thiamine Hydrochloride,
• Thiamin Mononitrate,
• Thiamine Mononitrate,
• Thiamine Nitrate,
• Thiaminium Chloride Hydrochloride,
• Tiamina, Vitamin B1,
• Vitamin B-1,
• Vitamina B1,
• Vitamine Anti-béribéri,
• Vitamine Antineuritique,
• Vitamine B1.

Groups at Risk of Thiamin Inadequacy

The following groups are among those most likely to have inadequate thiamin status.

People with alcohol dependence

In highly industrialized countries, chronic alcohol use disorders appear to be the most common cause of thiamin deficiency. Up to 80% of people with chronic alcoholism develop thiamin deficiency because ethanol reduces gastrointestinal absorption of thiamin, thiamin stores in the liver, and thiamin phosphorylation. Also, people with alcoholism tend to have inadequate intakes of essential nutrients, including thiamin.

Older adults

Up to 20%–30% of older adults have laboratory indicators that suggest some degree of thiamin deficiency. Possible reasons include low dietary intakes, a combination of chronic diseases, concomitant use of multiple medications, and low absorption of thiamin as a natural result of aging. Some small studies have found that the risk of deficiency is particularly high in elderly people who reside in an institution.

People with HIV/AIDS

People with HIV infection have an increased risk of thiamin deficiency and its sequelae, including beriberi and Wernicke-Korsakoff syndrome. Autopsies of 380 people with AIDS found that almost 10% had Wernicke’s encephalopathy, and some experts believe that thiamin deficiency is underdiagnosed in this population. The association between thiamin deficiency and HIV/AIDS is probably due to malnutrition as a result of the catabolic state associated with AIDS.

People with diabetes

Some small studies have found that thiamin levels in plasma are up to 76% lower in people with type 1 diabetes than in healthy volunteers and 50%–75% lower in people with type 2 diabetes. Other studies have shown a higher risk of thiamin deficiency in people with type 1 and/or type 2 diabetes based on tests of erythrocyte transketolase activity. These lower thiamin levels might be due to increases in clearance of thiamin by the kidneys. The relevance of these effects to clinical prognosis or outcomes is not known.

People who have undergone bariatric surgery

Bariatric surgery for weight loss is associated with some risks, including severe thiamin deficiency due to malabsorption that can lead to beriberi or Wernicke’s encephalopathy. A 2008 literature review identified 84 cases of Wernicke’s encephalopathy after bariatric surgery (primarily gastric bypass surgery) between 1991 and 2008. About half of these patients experienced long-lasting neurologic impairments. Micronutrient supplements that include thiamin are almost always recommended for patients following bariatric surgery to avoid deficiencies.

Thiamin and Health

This section focuses on four diseases or disorders in which thiamin does or might play a role: Wernicke-Korsakoff syndrome, diabetes, heart failure, and Alzheimer’s disease.

Wernicke-Korsakoff syndrome

Wernicke-Korsakoff syndrome is one of the most severe neuropsychiatric sequelae of alcohol abuse. The authors of a 2013 Cochrane Review of thiamin to treat or prevent Wernicke-Korsakoff syndrome found only two studies that met their inclusion criteria, and one of these studies has not been published. These randomized, double-blind, placebo-controlled trials compared 5 mg/day by mouth for 2 weeks or daily intramuscular doses of 5 to 200 mg/day thiamin over 2 consecutive days in a total of 177 people with a history of chronic alcohol use. The Cochrane Review authors concluded that the evidence from randomized clinical trials is insufficient to guide health care providers in selecting the appropriate dose, frequency, duration, or route of thiamin supplementation to treat or prevent Wernicke-Korsakoff syndrome in patients with alcohol abuse.

The authors of the European Federation of Neurological Societies guidelines for diagnosing, preventing, and treating Wernicke’s encephalopathy note that even high doses of oral thiamin supplements might not be effective in raising blood thiamin levels or curing Wernicke’s encephalopathy. They recommend 200 mg thiamin, preferably intravenously, three times daily (total of 600 mg/day) until the signs and symptoms stop, along with a balanced diet. In its guidelines for managing Wernicke’s encephalopathy in emergency departments, the Royal College of Physicians in London supports the administration of oral thiamin hydrochloride (100 mg three times a day) in patients with adequate dietary intakes of thiamin and no signs or symptoms of Wernicke’s encephalopathy. However, the authors recommend parenteral thiamin supplementation for patients at high risk, such as those with ataxia, confusion, and a history of chronic alcohol misuse, because oral supplementation is unlikely to produce adequate blood levels.

Diabetes

The proportion of people with type 1 or type 2 diabetes who have poor thiamin status based on erythrocyte transketolase activity ranges from 17% to 79% in studies conducted to date. In a study of 76 consecutive patients with type 1 or type 2 diabetes, for example, 8% had mild thiamin deficiency and 32% had moderate deficiency based on assays of the transketolase enzyme.

Some small studies have shown that oral supplementation with 150–300 mg/day thiamin can decrease glucose levels in patients with type 2 diabetes or impaired glucose tolerance. However, the authors of these studies did not assess the potential clinical significance of these findings.

A few small randomized studies have assessed the effects of benfotiamine supplements on diabetic neuropathy. Three studies found that, compared to placebo, 120–900 mg/day benfotiamine with or without other B-vitamins decreased the severity of neuropathy symptoms and lowered urinary albumin excretion (a marker of early-stage diabetic nephropathy). However, another study found no effect of 900 mg/day benfotiamine on urinary excretion of albumin or kidney injury molecule-1, a marker of kidney injury.

Well-designed studies with larger sample sizes and longer durations are required to determine whether thiamin supplements can reduce glucose levels in patients with diabetes or decrease diabetic compications.

Heart failure

The rates of poor thiamin status in patients with heart failure have ranged in studies from 21% to 98%. Explanations for this association include older age, comorbidities, insufficient dietary intake, treatment with diuretics, and frequent hospitalizations.

The authors of one study reported that 33% of 100 patients with chronic heart failure had thiamin deficiency compared to 12% of 50 healthy volunteers. Rates of deficiency were even higher when the investigators excluded those who used thiamin supplements. The different rates of thiamin deficiency in patients with heart failure in these and other studies are probably due to differences in nutrition status, comorbidities, medications and dietary supplements used, and techniques used to measure thiamin status.

The authors of a systematic literature review and meta-analysis found two randomized, double-blind, placebo-controlled trials of thiamin supplementation in people with heart failure that met their eligibility criteria. In these trials, thiamin supplements significantly improved net change in left ventricular ejection fraction. The authors did not assess the clinical significance of this finding, however.

More research is needed to determine whether thiamin supplements might benefit people with heart failure, even if they have normal thiamin status.

Alzheimer’s disease

According to animal model studies, thiamin deficiency might play a role in the development of Alzheimer’s disease. For example, thiamin deficiency produces oxidative stress in neurons, death of neurons, loss of memory, plaque formation, and changes in glucose metabolism—all markers of Alzheimer’s disease. Autopsy studies have shown that transketolase and other thiamin-dependent enzymes have decreased activity in the brains of people with Alzheimer’s disease.

Few studies have assessed the prevalence of thiamin deficiency in people with Alzheimer’s disease. One of these studies found that 13% of 150 patients with cognitive impairment and acute-onset behavioral disturbances were considered thiamin deficient based on plasma levels.

The authors of a 2001 Cochrane Review assessed three double-blind, randomized trials (including two crossover trials) that compared the effects of 3 g/day oral thiamin to placebo on cognitive function in patients with Alzheimer’s type dementia. The three studies randomly assigned fewer than 20 patients each, and the two crossover studies did not include a washout period. The review authors stated that it was not possible to draw any conclusions from these three studies because they were small and the publications describing them did not provide enough detail to combine these data in a meta-analysis.

Larger, well-designed studies are needed to determine whether thiamin supplements are beneficial for Alzheimer’s disease.

Health Risks from Excessive Thiamin

The body excretes excess amounts of thiamin in the urine. Because of the lack of reports of adverse effects from high thiamin intakes (50 mg/day or more) from food or supplements, the FNB did not establish ULs for thiamin. They hypothesize that the apparent lack of toxicity may be explained by the rapid decline in absorption of thiamin at intakes above 5 mg. However, the FNB noted that in spite of the lack of reported adverse events, excessive intakes of thiamin could have adverse effects.

Thiamin and Healthful Diets

The federal government’s 2020–2025 Dietary Guidelines for Americans notes that “Because foods provide an array of nutrients and other components that have benefits for health, nutritional needs should be met primarily through foods. … In some cases, fortified foods and dietary supplements are useful when it is not possible otherwise to meet needs for one or more nutrients (e.g., during specific life stages such as pregnancy).”

For more information about building a healthy dietary pattern, refer to the Dietary Guidelines for Americans and the USDA’s MyPlate.

The Dietary Guidelines for Americans describes a healthy dietary pattern as one that

• Includes a variety of vegetables; fruits; grains (at least half whole grains); fat-free and low-fat milk, yogurt, and cheese; and oils.
  • Many whole grains are good sources of thiamin, and yogurt contains thiamin.
• Includes a variety of protein foods such as lean meats; poultry; eggs; seafood; beans, peas, and lentils; nuts and seeds; and soy products.
  • ​​​​​​​Pork, fish, and seafood are good or high sources of thiamin. Beef, beans, and seeds contain thiamin.
• Limits foods and beverages higher in added sugars, saturated fat, and sodium.
• Limits alcoholic beverages.
• Stays within your daily calorie needs.

[1] – https://ods.od.nih.gov/factsheets/Thiamin-HealthProfessional/