Thiamine was the first B vitamin to be discovered by scientists… hence the “1”. Like the other B vitamins, thiamin is water-soluble and helps the body turn food into energy. You can find it in a variety of foods, as an individual supplement, and in multivitamins.

Thiamine is an essential nutrient, and all the tissues of the body, including the brain, need thiamine to function properly. The body needs thiamine to make adenosine triphosphate (ATP), a molecule that transports energy within cells.

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What Happens When You Don’t Get It?

A thiamine deficiency can seriously impact your nervous system, heart, and mental function. Thankfully, thiamine deficiency is uncommon in the developed world. While thiamine deficiency is rare in healthy adults, people suffering from specific medical conditions like alcoholism, Crohn's disease, and anorexia are more likely to not get enough of it. Those undergoing dialysis for their kidneys or taking loop diuretics are also at risk for thiamine deficiency. Loop diuretics, which are prescribed for people suffering from congestive heart failure, can flush thiamine out of the body, possibly canceling out any health benefits. The heart relies on thiamine to function properly. People who take digoxin and phenytoin should also be careful.

Thiamine deficiency can lead to two major health problems: beriberi and Wernicke-Korsakoff syndrome. Beriberi affects breathing, eye movements, heart function, and alertness. It’s caused by a buildup of pyruvic acid in the bloodstream, which is a side effect of your body not being able to turn food into fuel.

Wernicke-Korsakoff syndrome is technically two different disorders. Wernicke's disease affects the nervous system and causes visual impairments, a lack of muscle coordination, and mental decline. If Wernicke's disease is left untreated, it can lead to Korsakoff syndrome, which permanently impairs memory functions in the brain.

Either disease can be treated with thiamine injections or supplements. This may help with vision and muscular difficulties. However, thiamine can’t mend the permanent memory damage caused by Korsakoff syndrome.

What Can Supplements Do?

In the U.S., alcoholics are the most at risk for developing these diseases. Due to the fact that severe alcoholism can lead to thiamine deficiency, doctors use thiamine supplements to treat people going through major alcohol withdrawal.

Through its connection to Wernicke-Korsakoff syndrome, scientists have looked at thiamine as a possible treatment for Alzheimer's disease, but findings are inconclusive thus far. Thiamine, in use alongside other vitamin supplements, may also reduce the chances of developing cataracts.  Thiamine may also be helpful for those with diabetes who are at risk for kidney disease.

However, most people can get all the thiamine they need from food. Thiamine can be found in pork, poultry, peas, nuts, dried beans, soybeans, whole grain cereals, lentils, legumes, bread, rice, and yeast. Many whole grain products, such as cereals, breads, rice, and pasta, are fortified with thiamine. Although there are no real risk factors associated with thiamine consumption, certain foods can cancel out the body's usage of thiamine, leading to deficiency. Drinking lots of coffee or tea (even decaffeinated) can deplete the body of thiamine. Chewing tea leaves and betel nuts, as well as regularly eating raw fish and shellfish, can have similar effects.

Make sure you consult your doctor before starting a vitamin regimen and especially when using thiamine to treat a deficiency. In order to keep a balance of B vitamins in your system, medical professionals often suggest B complex vitamins over individual B supplements for healthy adults.