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Thiamin, also spelled thiamine and previously known as vitamin B1, is a micronutrient essential for the metabolism of carbohydrates that converts sugar into energy for the body and for normal nerve and heart function. Thiamine deficiency causes a condition known as beriberi or beri-beri. The initial symptoms are very vague. The first indication of thiamine deficiency may be simple fatigue. As the condition becomes more advanced, there is a wide range of symptoms, affecting many organ systems. These include, but are not limited to chest pains, memory loss, muscle cramps and weakness. In more advanced cases, muscle atrophy and heart failure may be present.
Thiamin has several important functions. It works with other B-group vitamins to help release energy from the food we eat and it keeps nerves and muscle tissue healthy. In the form of thiamin pyrophosphate (TPP), it plays an essential role as a cofactor in key reactions breaking down food and converting carbohydrate into energy for the body (carbohydrate metabolism). Like other B-complex vitamins, thiamin is also considered an anti-stress vitamin because it is believed to enhance the activity of the immune system and increase the body’s ability to resist stressful conditions.
Thiamin also plays a therapeutic role in the prevention or treatment of the following diseases:
- Alzheimer’s disease
- GALE ENCYCLOPEDIA OF DIETS Crohn’s disease
- congestive heart failure
- multiple sclerosis
Thiamin is a micronutrient, meaning a nutrient needed in very small amounts, found in a variety of animal and plant foods. It is a water-soluble vitamin that it is eliminated in urine when not needed by the body. Food must therefore supply it continuously. It belongs to a group of other water-soluble vitamins that are often present together and called B-complex. The other members of the vitamin B complex are riboflavin, niacin, pantothenic acid, biotin, pyridox-ine, folic acid, inositol, and vitamin B12. Important sources of thiamin are vegetables, wholegrain products, and nuts. The best sources are yeasts and liver and pork meat. Some specific good food sources of thiamin include (per 1 cup serving or as indicated):
- romaine lettuce (0.05 mg)
- asparagus, boiled (0.22 mg)
- spinach, boiled (0.17 mg)
- tuna (0.57 mg per 4 oz-serving)
- celery, raw (0.06 mg)
- green peas, boiled (0.41 mg)
- tomato (0.11 mg)
- eggplant, cooked (0.08 mg)
- brussels sprouts, boiled (0.17 mg per cup)
- baked beans, canned with pork (0.6 mg)
- cabbage, boiled (0.09 mg)
- watermelon (0.12 mg)
- red peppers, raw (0.06 mg per cup)
- carrots, raw (0.12 mg)
(Illustration by GGS Information Services/Thomson Gale.)
- summer squash, cooked (0.08 mg)
- winter squash, baked (0.17 mg)
- turnip greens, cooked (0.06 mg)
- broccoli, steamed (0.09 mg)
- green beans, boiled (0.09 mg)
- corn, cooked (0.36 mg)
- kale, boiled (0.07 mg per cup)
- lentils, cooked (0.33 mg)
- navy beans, cooked (0.37 mg)
- lima beans, cooked (0.30 mg)
- kidney beans, cooked (0.28 mg)
- black beans, cooked (0.42 mg per cup)
- oats, whole grain, cooked (0.26 mg per packet)
- pineapple (0.14 mg)
- oranges, each (0.11 mg)
- cauliflower, boiled (0.05 mg)
- split peas, cooked (0.37 mg)
- sesame seeds (0.56 mg per 1/2 cup)
- sunflower seeds (1.64 mg per 1/2 cup)
The Recommended Dietary Allowance (RDA) for thiamin is:
- infants: (0-6 months): 0.2 mg
- infants: (7-12 months): 0.3 mg
- children (1-3 y): 0.5 mg
- children (4-8 y): 0.6 mg
- children (9-13 y): 0.9 mg
- adolescents (14-18): males, 1.2 mg, females, 1.0 mg
- adults: males, 1.2 mg, females, 1.1 mg
- pregnancy: 1.4 mg
- lactation: 1.4 mg
Thiamin in nutritional supplements can be found in multivitamins, B-complex vitamins, or can be sold individually. It may be labeled as thiamine hydrochloride or thiamine mononitrate and is available in a variety of forms including tablets, softgels, and lozenges, including chewable and liquid drops. Two fat-soluble forms of thiamin are also used. They are thiamin propyl disulfide and thiamin tetrahydrofurfuryl disulphide, and are sometimes used in treatment of thiamin deficiency because they follow a different route of absorption into the body than water-soluble thiamin.
Oral thiamin is generally nontoxic, but stomach upset can occur with excessive intake. Thiamin deficiency may result from a deficiency in the diet. People whose diet consists mainly of polished white rice are at risk, because polishing removes almost all of the vitamins. Alcoholics, who often substitute alcohol for food, are also at high risk of developing thiamin deficiency. Symptoms include fatigue, irritability, memory impairment, appetite loss, sleep disturbances, abdominal discomfort, and weight loss. Severe thiamin deficiency, called beriberi, is characterized by nerve, heart, and brain abnormalities. One form, called dry beriberi, causes nerve and muscle abnormalities. Symptoms include prickling felt in the toes, a burning
sensation in the feet, very severe at night, pain, weakness, and wasting of leg muscles. The other form, wet beriberi, involves the heart and circulatory system and leads to heart abnormalities. Symptoms include a high output of blood from the heart, a fast heart rate, and dilation of blood vessels, making the skin warm and moist. Because the heart cannot maintain the high output, it becomes stressed and heart failure may occur, as well as abnormal fluid accumulation in the legs (edema) and in the lungs (congestion). If untreated, it leads to shock and death.
Thiamin is known to interact with the following medications and should not be taken at the same time:
- Antiacids. These medications may lower thiamin levels in the body by decreasing absorption and increasing excretion or metabolism.
- Tetracycline. Tetracyline is an antibiotic and thiamin taken either alone or in combination with other B vitamins interferes with its absorption by the body and action in the body.
- Antidepressants. Thiamin supplements may improve the action of antidepressants such as nortriptyline, especially in elderly patients. Other medications in this class of drugs include desimpramine and imipramine.
- Chemotherapy drugs. Laboratory studies suggest that thiamin may prevent the activity of chemotherapy drugs, but effects are not yet understood in people. Patients undergoing chemotherapy for cancer, especially people receiving fluorouracil-contain-ing drugs, are usually advised not take large doses of vitamin B1 supplements.
- Diuretics. Diuretics, especially furosemide, which belongs to a class of drugs called loop diuretics, may reduce the levels of thiamin in the body.
- Digoxin. Laboratory studies also suggest that digoxin, a drug used to treat heart conditions, may lower the ability of heart cells to absorb and use thiamin, especially if digoxin is combined with furosemide.
- Scopolamine. Thiamin may help reduce some of the side effects associated with scopolamine, a drug used to treat motion sickness.
Thiamin can also interact with food substances. Foods and beverages that may inactivate thiamin include those containing sulfites and tea, coffee and decaffeinated coffee. Consumption of betel nuts may also reduce thiamin activity due to chemical inactiva-tion, and may lead to symptoms of thiamin deficiency. Tobacco use also decreases thiamin absorption and may lead to decreased levels in the body.
All forms of thiamin deficiency are treated with supplements. If severe deficiency results in a medical emergency, it is treated with high doses of thiamin for several days. When alcoholics must be fed intravenously, they are often given supplements as a preventive measure. Doses for conditions, such as severe beriberi or alcoholism, are administered by a health care practitioner in an appropriate clinical setting. The symptoms of beriberi may recur years after apparent recovery.
Brain abnormalities due to thiamin deficiency are complications that occur mainly in alcoholics. They may develop when a chronic thiamin deficiency is suddenly worsened by a rapid decrease in the thiamin levels by an alcoholic binge or by a sudden increase in thiamin requirements when a malnourished alcoholic is fed intravenously. Brain abnormalities may develop in two stages: an early stage (Korsakoff’s syndrome) and a later stage (Wernicke’s encephalopathy). Together, they are called the Wernicke-Korsakoff syndrome. Korsakoff’s syndrome causes memory loss, and Wernicke’s encephalopathy causes mental confusion, difficulty walking, and eye problems. If Wernicke’s encephalopathy is not treated, symptoms may lead to coma and even death. As for excessive thiamin intake complications, rare hypersensitivity/allergic reactions have occurred with supplementation.
Parents should refrigerate fresh produce and keep milk and grains away from strong light because vitamins are easily destroyed and washed out during food preparation and storage. Vitamin supplements should also be stored at room temperature in a dry place.
Taking thiamin for a long period of time can result in an imbalance of other B-complex vitamins. This is why it is generally recommended to take a B-complex vitamin with thiamin. Because of the potential for side effects and interactions with medications, thiamin supplements should also be taken only under the supervision of a knowledgeable health care provider.
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Monique Laberge, Ph.D.