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Thiamin – Vitamin B1

What is thiamin?

Thiamin, also known as vitamin B1, is one of the B vitamins. Vitamin B1 is an essential nutrient, which means it needs to be obtained through the diet regularly to ensure optimal health. It is also a water-soluble vitamin, which means that it is not easily stored in the body and it must be consumed on a daily basis.

Where is thiamin found?

In many countries, thiamin is added to whole grains including brown rice, bread, lentils, and cereals. It is also added to fortified infant formulas. Additionally, thiamin is found naturally in pork and fish, as well as in trace amounts in fruit and milk.  Although cooking food can reduce its thiamin content, most of the sources of thiamin in the diet are already cooked or need to be cooked, so this is inevitable.

Thiamin can also be found in dietary supplements; either a multivitamin supplement containing thiamin, a vitamin B-complex supplement, or a thiamin supplement. Thiamin is available in supplements as water-soluble thiamin mononitrate and thiamin hydrochloride or fat-soluble benfotiamine. All forms are converted to thiamin in the body.

Why is thiamin important?

Thiamin is essential to many bodily functions. Vitamin B1 is important for the metabolism of food, as it helps break down sugars, fats, and amino acids so that they can be converted to fuel for the cells. For this reason, thiamin is vital in keeping cells healthy and functioning properly.

Thiamin also helps the nervous system and brain function, as one of its metabolites thiamin triphosphate is essential to the health of neuronal membranes. 

What is the RDA for thiamin?

The Recommended Dietary Allowance (RDA) for thiamin is 1.2 mg daily for men, 1.1 mg for women, and 1.4 mg for pregnant and lactating women. The RDA for thiamin is 0.9 mg for children between nine and thirteen years of age, 0.6 mg for children four to eight years of age, 0.5 mg for children one to three years of age, 0.3 mg for infants between seven and twelve months, and 0.2 mg for infants under six months of age. The RDA for thiamin for infants can be met through breast milk or infant formula.

These values are given by the National Institutes of Health, and the RDA represents the daily intake sufficient to meet the dietary needs of 97-98% of healthy individuals. You can meet the RDA for thiamin by consuming whole grains on a regular basis, as one half cup of thiamine-enriched white rice contains 117 percent of the daily RDA.

How much is too much?

Since thiamin is a water-soluble vitamin, the risk for serious toxicity is very low. In addition, the absorption of thiamin decreases significantly at high doses above 5 mg. For this reason, there is no established Upper Limit (UL) for the daily intake of thiamin. However, this does not mean that side effects of consuming excess thiamin cannot occur. 

The UL represents the maximum daily intake that is unlikely to cause negative health problems.

What are the benefits of thiamin?

Thiamin supplementation has been used as a treatment for a neuropsychiatric condition called Wernicke-Korsakoff syndrome (WKS), which is sometimes observed in chronic alcoholics.  However, the evidence on whether or not this is effective as well as the proper therapeutic dose is inconclusive.

Another study found that type 2 diabetes patients given high doses of thiamin supplements showed improved glucose tolerance and lower fasting blood glucose. This makes sense because thiamin plays a role in carbohydrate metabolism. More research is needed to determine whether or not this is an effective treatment and what dose would be effective.

One study found that thiamine deficiency is common in individuals with congestive heart failure.  In addition, the same study found that thiamin supplementation improved left ventricular ejection fraction rates in a group of patients with congestive heart failure compared to a placebo. This was a small study, however, so larger studies are needed to determine whether thiamin supplementation is helpful for this purpose. 

Thiamin deficiency

Thiamin deficiency is fairly rare in the North America, as most grains are fortified with thiamin. However, the following groups are more at risk for deficiency than others.

People with chronic alcoholism are at risk for thiamin deficiency because ethanol decreases thiamin absorption. Additionally, people with chronic alcoholism are more likely to have diets that are nutritionally inadequate.

Older people might have an increased risk of thiamin deficiency due to decreased absorption of thiamin due to age, medications, and higher rates of chronic disease. 

People who have undergone weight loss or bariatric surgery may have an elevated risk of thiamin deficiency due to reduced absorption of many nutrients including thiamin. For this reason, people who have undergone bariatric surgery are often given vitamin supplements to ensure optimal health outcomes.

Thiamin deficiency has been shown to be higher in people with certain medical conditions including HIV/AIDS and diabetes.

Chronic severe thiamin deficiency can result in a condition called beriberi, which causes muscle wasting and peripheral neuropathy, or decreased sensation in the hands and feet. Mild thiamin deficiencies may have side effects including unexplained weight loss, decreased immunity, confusion, muscle weakness, and peripheral neuropathy described above.

Thiamin supplementation

Thiamin deficiency can be corrected with high doses of thiamin supplements or injections in combination with a balanced diet. 

If you think you are deficient in thiamin or at risk for deficiency, consider getting your blood levels tested. As always, consult your doctor before you begin taking any vitamin or mineral supplement, to make sure your medications or health conditions don’t make it a serious risk. 


Alaei Shahmiri, F., Soares, M. J., Zhao, Y., & Sherriff, J. (2013). High-dose Thiamine Supplementation Improves Glucose Tolerance in Hyperglycemic Individuals: A Randomized, Double-Blind Cross-Over Trial. Eur J Nutr, 52(7), 1821-1824. doi:10.1007/s00394-013-0534-6

Butterworth, R. F. (2003). Thiamin Deficiency and Brain Disorders. Nutr Res Rev, 16(2), 277-284. doi:10.1079/NRR200367

Day, E., Bentham, P. W., Callaghan, R., Kuruvilla, T., & George, S. (2013). Thiamine for Prevention and Treatment of Wernicke-Korsakoff Syndrome in People who Abuse Alcohol. Cochrane Database Systemic Review, 2013(7). doi:10.1002/14651858.CD004033.pub3

Dinicolantonio, J. J., Lavie, C. J., Niazi, A. K., O’Keefe, J. H., & Hu, T. (2013). Effects of Thiamine on Cardiac Function in Patients With Systolic Heart Failure: Systematic Review and Metaanalysis of Randomized, Double-Blind, Placebo-Controlled Trials. Oschner J., 13(4), 495-499.

Manzetti, S., Zhang, J., & Van der Spoel, D. (2014). Thiamin function, metabolism, uptake, and transport. Biochemistry,53(5), 821-835. doi:10.1021/bi401618y

Thiamin – Fact sheet for health professionals. (2020, June 3). Retrieved July 03, 2020, from

Thiamin – Vitamin B1. (n.d.). Retrieved July 03, 2020, from

Xanthakos, S. A. (200). Nutritional Deficiencies in Obesity and After Bariatric Surgery. Pediatric Clin North Am, 56(5), 1105-1121. doi:10.1016/j.pcl.2009.07.002



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