Thiamine, also known as vitamin B1, was the first of the water-soluble B-vitamin family to be discovered. It is an essential component of an enzyme, thiamine pyrophosphate, that is involved in metabolizing carbohydrates. Thiamine works closely with other B vitamins to assist in the utilization of proteins and fats as well, and helps mucous membranes and the heart to stay healthy. The brain relies on thiamine's role in the conversion of blood sugar (glucose) into biological energy to function properly. Thiamine is also involved in certain key metabolic reactions occurring in nervous tissue, the heart, in the formation of red blood cells, and in the maintenance of smooth and skeletal muscle.
The recommended daily allowance (RDA) of thiamine is 0.3 mg for infants less than six months old, 0.4 mg for those from six months to one year old, 0.7 mg for children ages one to three years, 0.9 mg for those four to six years, and 1.0 mg for those seven to 10 years. Requirements vary slightly by gender after age 10. Males need 1.3 mg from 11 to 14 years, 1.5 mg from 15 to 50 years, and 1.2 mg when over age 50 years. Females require 1.1 mg from 11 to 50 years of age, and 1.0 mg if older than 50 years. The RDA is slightly higher for women who are pregnant (1.5 mg) or lactating (1.6 mg). Adults need a minimum of 1.0 mg of thiamine a day, but
Thiamine has limited therapeutic use apart from supplements for people who are deficient or have significant risk factors for deficiency, such as alcoholism. High doses are used to treat some metabolic disorders, including certain enzyme deficiencies, Leigh's disease, and maple syrup urine disease. People suffering from diabetic neuropathy may sometimes benefit from additional thiamine. This supplementation should be taken only on the advice of a healthcare provider. Claims have been made that it can also help people with Alzheimer's disease, epilepsy, canker sores, depression, fatigue, fibromyalgia, and motion sickness. Improvement of these conditions based on supplementation with thiamine is unsubstantiated. Although a deficiency of thiamine may cause canker sores, taking extra amounts of the vitamin after they appear does not seem to help them heal.
While all plant and animal foods have thiamine, higher levels of thiamine are found in many nuts, seeds, brown rice, seafood, and whole-grain products. Sunflower seeds are a particularly good source. Grains are stripped of the B vitamin content during processing, but it is often added back to breads, cereals, and baked goods. Legumes, milk, beef liver, and pork are other foods with high vitamin B1 content. Thiamine is destroyed by prolonged high temperatures, but not by freezing. Food should be cooked in small amounts of water so that thiamine and other water-soluble vitamins don't leach out. Baking soda should not be added to vegetables, and fresh foods should be eaten to avoid sulfite preservatives. Both of these chemicals will break down the thiamine content found in foods. Drinking tea or alcohol with a meal will also drastically decrease the amount of thiamine that is absorbed by the body.
Thiamine is available in oral, intramuscular injectable, and intravenous formulations. Injectable formulas are usually preserved for persons who are severely thiamine deficient. Supplements should always be stored in a cool dry place, away from direct light, and out of the reach of children.
A deficiency of thiamine leads to a condition known as beriberi. Once common in sailors, it has become rare in the industrialized parts of the world except in cases of alcoholism and certain disease conditions. Beriberi is, however, frequently found in refugee camps and similar shelters for displaced persons. Infantile beriberi is presently the leading cause of death among the children of ethnic minority groups in southeast Asia. The syndrome typically causes poor appetite, abdominal pain, heart enlargement, constipation, weakness, swelling of limbs, muscle spasms, insomnia, and memory loss. Under treatment, the condition can resolve very quickly. Untreated beriberi will lead eventually to Wernicke-Korsakoff syndrome. These patients experience confusion, disorientation, inability to speak, gait difficulties, numbness or tingling of extremities, edema, nausea, vomiting, visual difficulties, and may progress to psychosis, coma, and death. Even in advanced states, this condition can be reversible if thiamine is given, nutritional status is improved, and use of alcohol is stopped.
Risk factors for deficiency
The leading risk factor for developing a deficiency of thiamine is alcoholism. Generally, alcoholics eat poorly, and therefore have a low dietary intake of thiamine and other vitamins to begin with. Alcohol also acts directly to destroy thiamine and increases the excretion of it. People with cirrhosis of the liver, malabsorption syndromes, diabetes, kidney disease, chronic infections, or hypermetabolic conditions also have increased susceptibility to thiamine deficiency. The elderly are more prone to poor nutritional status as well as difficulties with absorption, and may need a supplement. Others with nutritionally inadequate diets, or an increased need as a result of stress, illness, or surgery may benefit from additional vitamin B1 intake since utilization is higher under these conditions. Those who diet or fast frequently may also be at risk for low levels of thiamine. Use of tobacco products, or carbonate and citrate food additives can impair thiamine absorption. A shortage of vitamin B1 is likely to be accompanied by a shortage of other B vitamins, and possibly other nutrients as well. A supplement containing a balance of B complex and other vitamins is usually the best approach unless there is a specific indication for a higher dose of thiamine, or other individual vitamins.
Thiamine should not be taken by anyone with a known allergy to B vitamins, which occurs rarely.
In very unusual circumstances, large doses of thiamine may cause rashes, itching, or swelling. These reactions are more common with intravenous injections than oral supplements. Most people do not experience any side effects from oral thiamine.
Oral contraceptives, antibiotics, sulfa drugs, and certain types of diuretics may lower thiamine levels in the body. Consult a health care professional about the advisability of supplementation. Taking this vitamin may also intensify the effects of neuromuscular blocking agents that are used during some surgical procedures. B vitamins are best absorbed as a complex, and magnesium also promotes the absorption of thiamine.
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Rebecca J. Frey, PhD