vitamin b1

Vitamin B1, also called thiamin (or thiamine), is an essential water-soluble B vitamin. The NIH Office of Dietary Supplements describes it as helping the body convert food into energy and as important for the growth, development, and function of the body's cells. In supplements it appears in multivitamin/mineral products, in B-complex products, or on its own, most commonly as thiamin mononitrate or thiamin hydrochloride; some products use benfotiamine, a synthetic thiamin derivative that is converted to thiamin in the body. Most people in the United States get enough thiamin from foods such as whole grains, fortified breads and cereals, pork, fish, legumes, seeds, and nuts, and deficiency is rare in this country.

Thiamin's established, evidence-backed role is preventing and treating thiamin deficiency; according to the NIH ODS, supplemental thiamin (often given parenterally, by injection) rapidly resolves beriberi. Beyond correcting deficiency, the evidence is preliminary, and the NIH frames it cautiously. ODS says scientists "are studying" whether thiamin or benfotiamine can help blood sugar and diabetic nerve damage, but states that larger, longer, better-designed studies are still needed and that the small studies done so far did not assess the clinical significance of their findings. For heart failure, ODS says more research is needed, including in people with normal thiamin status. For Alzheimer's disease, it says larger, well-designed studies are needed and that whether thiamin helps mental function "needs further study." A 2013 Cochrane Review also concluded that evidence from randomized trials is insufficient to guide thiamin dosing for treating or preventing Wernicke-Korsakoff syndrome. Do not assume thiamin supplements treat any of these conditions in people who are not deficient.

Recommended Dietary Allowances (RDAs) are about 1.2 mg/day for adult men and 1.1 mg/day for adult women, rising to 1.4 mg/day during pregnancy and breastfeeding, according to the NIH; these amounts are meant to meet normal nutritional needs, not to treat disease. Some research has used much higher amounts (for example, 150-300 mg/day of thiamin for type 2 diabetes, or higher doses of benfotiamine), but these are investigational and not established as effective. There is no Tolerable Upper Intake Level for thiamin. Talk to your doctor, pharmacist, or a registered dietitian before starting thiamin supplements, including to decide whether you need one at all and at what dose; deficiency states such as Wernicke-Korsakoff syndrome require professional medical treatment.

According to the NIH ODS, thiamin has not been shown to cause harm, and the body removes excess thiamin in the urine. Because there were no reports of adverse effects from high intakes (50 mg/day or more) from food or supplements, the Food and Nutrition Board did not set a Tolerable Upper Intake Level; ODS notes that absorption of thiamin drops sharply above about 5 mg, which may help explain the apparent lack of toxicity. Even so, the Board cautioned that, despite the absence of reported problems, excessive intakes of thiamin could have adverse effects. This information is general and is not a substitute for medical advice.

The NIH ODS does not list specific side effects from oral thiamin and says it has not been shown to cause harm, with excess amounts excreted in the urine. As with any supplement, individual reactions are possible, so report any unusual symptoms to your health care provider. Note that symptoms often linked with thiamin (such as memory loss, confusion, muscle weakness, and tingling in the hands and feet) are signs of deficiency, not side effects of taking the vitamin.

According to the NIH ODS, thiamin is not known to interact with any medications, but some medications can lower thiamin levels in the body. Examples include the loop diuretic furosemide (Lasix), which can increase urinary loss of thiamin, and the chemotherapy drug fluorouracil (5-fluorouracil, Adrucil). People who take these or other medications regularly should discuss their thiamin status with their providers. Tell your doctor and pharmacist about all supplements and prescription or over-the-counter medicines you take so they can check for possible interactions.