Vitamin B1, also called thiamine or thiamin, is one of 8 B vitamins. All B vitamins help the body convert food (carbohydrates) into fuel (glucose), which the body uses to produce energy. These B vitamins, often referred to as B-complex vitamins, also help the body metabolize fats and protein. B-complex vitamins are needed for a healthy liver, skin, hair, and eyes. They also help the nervous system function properly and are needed for good brain function.
All B vitamins are water soluble, meaning that the body does not store them.
Like other B-complex vitamins, thiamine is sometimes called an "anti-stress" vitamin because it may strengthen the immune system and improve the body's ability to withstand stressful conditions. It is named B1 because it was the first B vitamin discovered.
Thiamine is found in both plants and animals and plays a crucial role in certain metabolic reactions. Your body needs it to form adenosine triphosphate (ATP), which every cell of the body uses for energy.
It is rare to be deficient in thiamine, although alcoholics, people with Crohn disease, anorexia, and those undergoing kidney dialysis may be deficient. Symptoms of thiamine deficiency are:
- Abdominal discomfort
People with thiamine deficiency also have trouble digesting carbohydrates. This allows a substance called pyruvic acid to build up in the bloodstream, causing a loss of mental alertness, difficulty breathing, and heart damage, a disease known as beriberi.
The most important use of thiamine is to treat beriberi, which is caused by not getting enough thiamine in your diet. Symptoms include:
- Swelling, tingling, or burning sensation in the hands and feet
- Trouble breathing because of fluid in the lungs
- Uncontrolled eye movements (nystagmus)
People in the developed world usually do not get beriberi because foods such as cereals and breads are fortified with vitamin B1.
Wernicke-Korsakoff syndrome is a brain disorder caused by thiamine deficiency. Wernicke-Korsakoff is actually two disorders. Wernicke disease involves damage to nerves in the central and peripheral nervous systems. It is often caused by malnutrition due to alcoholism. Korsakoff syndrome is characterized by memory problems and nerve damage. High doses of thiamine can improve muscle coordination and confusion, but rarely improves memory loss.
Preliminary evidence suggests that thiamine, along with other nutrients, may lower the risk of developing cataracts. People with plenty of protein and vitamins A, B1, B2, and B3 (or niacin) in their diet are less likely to develop cataracts. Getting enough vitamins C, E, and B complex vitamins, particularly B1, B2, B9 (folic acid), and B12, may further protect the lens of your eyes from developing cataracts. More research is needed.
Lack of thiamine can cause dementia in Wernicke-Korsakoff syndrome. So researchers have speculated that thiamine might help Alzheimer disease. Oral thiamine has been shown to improve cognitive function of patients with Alzheimer. However, absorption of thiamine is poor in elderly individuals. More research is needed before thiamine can be proposed as a treatment for Alzheimer disease.
Thiamine may be related to heart failure because many people with heart failure take diuretics (water pills), which help rid the body of excess fluid. But diuretics may also cause the body to get rid of too much thiamine. A few small studies suggest that taking thiamine supplements may help. Taking a daily multivitamin should provide enough thiamine.
Low levels of thiamine are associated with depression. In one study of elderly Chinese adults, poor thiamine levels were associated with a higher risk of depression.
Vitamin B1 can be found in multivitamins (including children's chewable and liquid drops), B complex vitamins, or it can be sold individually. It is available in a variety of forms, including tablets, soft gels, and lozenges. It may also be labeled as thiamine hydrochloride or thiamine mononitrate. In cases of severe deficiency, thiamine can be administered intravenously.
As with all medications and supplements, check with your health care provider before giving vitamin B1 supplements to a child.
Daily recommendations for dietary vitamin B1, according to the National Academy of Sciences, are as follows:
- Newborns, 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)
- Men, 14 to 18 years: 1.2 mg (RDA)
- Women, 14 to 18 years: 1 mg (RDA)
- Men, 19 years and older: 1.2 mg (RDA)
- Women, 19 years and older: 1.1 mg (RDA)
- Pregnant or breastfeeding women: 1.4 mg (RDA)
Doctors determine the appropriate doses for conditions like beriberi and Wernicke-Korsakoff syndrome. Doctors give thiamine intravenously for Wernicke-Korsakoff syndrome.
A daily dose of 50 to 100 mg is often taken as a supplement. Thiamine appears safe in these doses. But you should talk to your doctor before taking a large amount.
Because of the potential for side effects and interactions with medications, you should take dietary supplements only under the supervision of a knowledgeable health care provider.
Thiamine is generally safe. Very high doses may cause stomach upset.
Taking any one of the B vitamins for a long period of time can result in an imbalance of other important B vitamins. For this reason, you may want to take a B-complex vitamin, which includes all the B vitamins.
If you are currently taking any of the following medications, you should not use vitamin B1 without first talking to your doctor.
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 (Lasix, a loop diuretic).
Diuretics (water pills): Diuretics, particularly furosemide (Lasix), which belongs to a class called loop diuretics, may reduce levels of vitamin B1 in the body. It is possible that other diuretics may have the same effect. If you take a diuretic, ask your doctor if you need a thiamine supplement.
Phenytoin (Dilantin): Preliminary evidence suggests that some people taking phenytoin have lower levels of thiamine in their blood, which may contribute to the side effects of the drug. However, this is not true of all people who take phenytoin. If you take phenytoin, ask your doctor if you need a thiamine supplement.
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