Vitamin B1, also called thiamine, is one of eight water-soluble B vitamins. All B vitamins help the body to convert carbohydrates into glucose (sugar), which is "burned" to produce energy. These B vitamins, often referred to as B complex vitamins, are essential in the breakdown of fats and protein. B complex vitamins also play an important role in maintaining muscle tone along the wall of the digestive tract and promoting the health of the nervous system, skin, hair, eyes, mouth, and liver.

Similar to some other B complex vitamins, thiamine is considered an "anti-stress" vitamin because it is believed to enhance the activity of the immune system and improve the body's ability to withstand stressful conditions.

Thiamine is found in both plants and animals and plays a crucial role in certain metabolic reactions, particularly, as mentioned, the conversion of carbohydrates (starches) into energy. For example, thiamine is essential during exercise, when energy expenditure is high.

Thiamine deficiency is rare, but tends to occur in people who get most of their calories from sugar or alcohol. Individuals with thiamine deficiency have difficulty digesting carbohydrates. As a result, a substance called pyruvic acid builds up in the bloodstream, causing a loss of mental alertness, difficulty breathing, and heart damage. In general, thiamine supplements are primarily used to treat this deficiency known as beriberi.

Beriberi
The most important use of thiamine is in the treatment of beriberi, a condition caused by a deficiency of thiamine in the diet. Symptoms include swelling, tingling or burning sensation in the hands and feet, confusion, difficulty breathing (from fluid in the lungs), and uncontrolled eye movements (called nystagmus).

Wernicke-Korsakoff syndrome
Wernicke-Korsakoff syndrome is a brain disorder caused by thiamine deficiency. Replacing thiamine alleviates the symptoms of this syndrome. Wernicke-Korsakoff is actually two disorders in one: (1) Wernicke's disease involves damage to nerves in the central and peripheral nervous systems and is generally caused by malnutrition (particularly a lack of thiamine) associated with habitual alcohol abuse, and (2) Korsakoff syndrome is characterized by memory impairment with various symptoms of nerve damage. High doses of thiamine can improve muscle incoordination and confusion associated with this disease, but only rarely improves the memory loss.

Cataracts
Dietary and supplemental vitamin B2, along with other nutrients, is important for normal vision and prevention of cataracts (damage to the lens of the eye which can lead to cloudy vision). In fact, people with plenty of protein and vitamins A, B1, B2, and B3 (niacin) in their diet are less likely to develop cataracts. Plus, taking additional supplements of vitamins C, E, and B complex (particularly the B1, B2, B9 [folic acid], and B12 [cobalamin] in the complex ) may further protect the lens of your eyes from developing cataracts.

Burns
It is especially important for people who have sustained serious burns to obtain adequate amounts of nutrients in their daily diet. When skin is burned, a substantial percentage of micronutrients may be lost. This increases the risk for infection, slows the healing process, prolongs the hospital stay, and even increases the risk of death. Although it is unclear which micronutrients are most beneficial for people with burns, many studies suggest that a multivitamin including the B complex vitamins may aid in the recovery process.

Heart failure
Thiamine may be related to heart failure in two ways. First, low levels of thiamine may contribute to the development of congestive heart failure (CHF). On the flip side, people with severe heart failure can lose a significant amount of weight including muscle mass (called wasting or cachexia) and become deficient in many nutrients. It is not known whether taking thiamine supplements would have any bearing on the development or progression of CHF and cachexia. Eating a balanced diet, including thiamine, and avoiding things that deplete this nutrient, such as high amounts of sugar and alcohol, seems prudent, particularly for those at the early stages of CHF.

Other
Some scientists have speculated that thiamine may have some benefit in treating Alzheimer's disease. This theory is based on the effects that this nutrient has on the brain and the symptoms that people develop when deficient in thiamine. The studies on this subject to date are limited in number and inconclusive, however. Much more research would be needed before anything could be said regarding a possible use for thiamine in treating Alzheimer's disease.

Limited quantities of thiamine can be found in most foods, but large amounts of this vitamin can be found in pork and organ meats. Other good dietary sources of thiamine include whole-grain or enriched cereals and rice, wheat germ, bran, brewer's yeast, and blackstrap molasses.

Vitamin B1 can be found in multivitamins (including children's chewable and liquid drops), B complex vitamins, or can be sold individually. It is available in a variety of forms including tablets, softgels, and lozenges. It may also be labeled as thiamine hydrochloride or thiamine mononitrate.

As with all medications and supplements, check with a healthcare provider before giving vitamin B1 supplements to a child.

Daily recommendations for dietary vitamin B1 are listed below.

Pediatric

• Newborns to 6 months: 0.2 mg (adequate intake)
• Infants 7 months to 1 year: 0.3 mg (adequate intake)
• Children 1 to 3 years: 0.5 mg (RDA)
• Children 4 to 8 years: 0.6 mg (RDA)
• Children 9 to 13 years: 0.9 mg (RDA)
• Males 14 to 18 years: 1.2 mg (RDA)
• Females 14 to 18 years: 1 mg (RDA)

Adult

• Males 19 years and older: 1.2 mg (RDA)
• Females 19 years and older: 1.1 mg (RDA)
• Pregnant females: 1.4 mg (RDA)
• Breastfeeding females: 1.5 mg (RDA)

Doses for conditions like beriberi and Wernicke-Korsakoff syndrome are decided by a healthcare practitioner in an appropriate clinical setting. For Wernicke-Korsakoff syndrome, thiamine is administered by venous injection.

Because of the potential for side effects and interactions with medications, dietary supplements should be taken only under the supervision of a knowledgeable healthcare provider.

Oral vitamin B1 is generally nontoxic. Stomach upset can occur at very high doses (much higher than the recommended daily amount).

Taking any one of the B complex vitamins for a long period of time can result in an imbalance of other important B vitamins. For this reason, it is generally important to take a B complex vitamin with any single B vitamin.

If you are currently being treated with any of the following medications, you should not use vitamin B1 without first talking to your healthcare provider.

Antibiotics, Tetracycline
Vitamin B1 should not be taken at the same time as the antibiotic tetracycline because it interferes with the absorption and effectiveness of this medication. Vitamin B1 either alone or in combination with other B vitamins should be taken at different times from tetracycline. (All vitamin B complex supplements act in this way and should therefore be taken at different times from tetracycline.)

Antidepressant Medications, Tricylic
Taking vitamin B1 supplements may improve treatment with antidepressants such as nortriptyline, especially in elderly patients. Other medications in this class of antidepressants include desimpramine and imipramine.

Chemotherapy
Although the significance is not entirely clear, laboratory studies suggest that thiamine may inhibit the anti-cancer activity of chemotherapy agents. How this will ultimately prove relevant to people is not known. However, it may be wise for people undergoing chemotherapy for cancer to not take large doses of vitamin B1 supplements.

Digoxin
Laboratory studies suggest that digoxin (a medication used to treat heart conditions) may reduce the ability of heart cells to absorb and use vitamin B1; this may be particularly true when digoxin is combined with furosemide (a loop diuretic).

Diuretics
Diuretics (particularly furosemide, which belongs to a class called loop diuretics) may reduce the levels of vitamin B1 in the body. In addition, similar to digoxin, furosemide may diminish the heart's ability to absorb and utilize vitamin B1, especially when these two medications are combined.

Scopolamine
Vitamin B1 may help reduce some of the side effects associated with scopolamine, a medication commonly used to treat motion sickness.

Ambrose, ML, Bowden SC, Whelan G. Thiamin treatment and working memory function of alcohol-dependent people: preliminary findings. Alcohol Clin Exp Res. 2001;25(1):112-116.

Antoon AY, Donovan DK. Burn Injuries. In: Behrman RE, Kliegman RM, Jenson HB, eds. Nelson Textbook of Pediatrics. Philadelphia, Pa: W.B. Saunders Company; 2000:287-294.

Bell I, Edman J, Morrow F, et al. Brief communication. Vitamin B1, B2, and B6 augmentation of tricyclic antidepressant treatment in geriatric depression with cognitive dysfunction. J Am Coll Nutr. 1992;11:159-163.

Boros LG, Brandes JL, Lee W-N P, et al. Thiamine supplementation to cancer patients: a double-edged sword. Anticancer Res. 1998;18:595–602.

Cumming RG, Mitchell P, Smith W. Diet and cataract: the Blue Mountains Eye Study.
Ophthalmology. 2000;107(3):450-456.

De-Souza DA, Greene LJ. Pharmacological nutrition after burn injury. J Nutr. 1998;128:797-803.

Jacques PF, Chylack LT Jr, Hankinson SE, et al. Long-term nutrient intake and early age-related nuclear lens opacities. Arch Ophthalmol. 2001;119(7):1009-1019.

Kelly GS. Nutritional and botanical interventions to assist with the adaptation to stress. Alt Med Rev. 1999;4(4):249-265.

Kirschmann GJ, Kirschmann JD. Nutrition Almanac. 4th ed. New York: McGraw-Hill;1996:80-83.

Kuzniarz M, Mitchell P, Cumming RG, Flood VM. Use of vitamin supplements and cataract: the Blue Mountains Eye Study. Am J Ophthalmol. 2001;132(1):19-26.

Leslie D, Gheorghiade M. Is there a role for thiamine supplementation in the management of heart failure? Am Heart J. 1996;131:1248–1250.

Lindberg MC, Oyler RA. Wernick's encephalopathy. Am Fam Physician. 1990;41:1205–1209.

Lubetsky A, Winaver J, Seligmann H, et al. Urinary thiamine excretion in the rat: effects of furosemide, other diuretics, and volume load [see comments]. J Lab Clin Med. 1999;134(3):232-237.

Meador KJ, Nichols ME, Franke P, et al. Evidence for a central cholinergic effect of high-dose thiamine. Ann Neurol. 1993;34:724-726.

Meyer NA, Muller MJ, Herndon DN. Nutrient support of the healing wound. New Horizons. 1994;2(2):202-214.

National Academy of Science. Recommended Daily Allowances. Accessed at http://www.nal.usda.gov/fnic/dga/index.html on January 4, 1999.

Nutrients and Nutritional Agents. In: Kastrup EK, Hines Burnham T, Short RM, et al, eds. Drug Facts and Comparisons. St. Louis, Mo: Facts and Comparisons; 2000:4-5.

Omray A. Evaluation of pharmacokinetic parameters of tetracycline hydrochloride upon oral administration with vitamin C and vitamin B complex. Hindustan Antibiot Bull. 1981;23(VI):33-37.

Ott BR, Owens NJ. Complementary and alternative medicines for Alzheimer's disease. J Geriatr Psychiatry Neurol. 1998;11:163-173.

Rieck J, Halkin H, Almog S, et al. Urinary loss of thiamine is increased by low doses of furosemide in healthy volunteers. J Lab Clin Med. 1999;134(3):238-243.

Rodriquez-Martin JL, Qizilbash N, Lopez-Arrieta JM. Thiamine for Alzheimer's disease (Cochrane Review). Cochrane Database Syst Rev. 2001;2:CD001498.

Witte KK, Clark AL, Cleland JG. Chronic heart failure and micronutrients. J Am Coll Cardiol. 2001;37(7):1765-1774.

Zangen A, Botzer D, Zanger R, Shainberg A. Furosemide and digoxin inhibit thiamine uptake in cardiac cells. Eur J Pharmacol. 1998;361(1):151-155.