Vitamin B1 ( thiamine )

Vitamin B1 ( Thiamine ) happens to be one of the coenzymes which plays a vital role in the energy-producing process. Its primary function is as part of a coenzyme system that makes possible carbohydrate metabolism. You can think of thiamine as one of the spark plugs that keeps the energy-producing functions of the body going. Thiamine also plays a role in the excitation of nerves.

The "classic" syndrome of thiamine deficiency is beriberi. There are many forms of beriberi: dry beriberi, in which the principal lesions include muscular atrophy and inflammation of the nerve endings; wet beriberi, with general edema and internal effusions sometimes complicated with myocardial insufficiency; infantile beriberi; and a combination of wet and dry beriberi.

Thiamine deficiency also depresses protein synthesis in the brain and organs and depresses the uptake of two neurotransmitters, acetylcholine and serotonin, by the nerve synapses in the brain. Without these chemicals, the transmission of nerve impulses is seriously impaired.

Thiamine deficiency also results in derangement of the appetite mechanisms, so that the sufferer loses the will to eat. This effect is directly related to the inhibition of carbohydrate metabolism. When the "engine" is stalled, its desire for fuel necessarily dies right along with it.

Since the cells must operate at greatly reduced efficiency when the body's thiamine supply is inadequate, the production of cellular antibodies-an important part of the body's immune system-is severely diminished.

The first symptom that thiamine demand exceeds supply is called neurasthenia, which is "doctorese" for nervous exhaustion. Appetite, memory, initiative, concentration, and temper are gradually lost right along with energy. They're replaced with fatigue and depression. Pains in the abdomen and chest follow. As the deficiency gets worse, "pins and needles" begin in the toes and burning sensations begin in the feet. What's happening is that the nerve pathways are degenerating. First the nerves go, then the muscles. The sense of touch seems to disappear, except that certain muscles in the legs start to feel very tender. Walking becomes more than a chore. And since the heart is a muscle, it starts to die, too.

Beriberi has existed for thousands of years, but up until the last half of the nineteenth century, it was a disease primarily of the rich. We usually don't think of rich people as suffering from nutritional deficiencies, but many of the B vitamin deficiencies were suffered by the upper classes for centuries before they were "handed down" to the poor. The reason for this is that only the rich could afford refined food such as white rice and flour-up until the nineteenth century, when milling of grain became widespread and inexpensive. So when millions of people began to depend on polished rice, which is practically devoid of thiamine, instead of brown rice, beriberi became a disease of the masses.

The body's requirement for thiamine is dependent upon two factors: the caloric content of the diet, especially with regard to carbohydrates, and the amount of energy expended. So someone eating a high carbohydrate diet and using a lot of energy needs more thiamine than someone who eats very little carbohydrate and sits still all day. Of course, there is a bottom-line require- ment for thiamine, which even the sedentary person who doesn't eat much has to fulfill. That baseline, the RDA, is one mg. (Actually, the RDA is set at .5 mg. for every 1000 calories in the daily diet.)

But many factors can enter the picture and raise that requirement. Pregnant and lactating women need more thiamine. Alcoholics are at great risk for thiamine deficiency. Alcohol metabolizes as a carbohydrate, so it burns up B vitamins but doesn't replace them. An equal caloric load of whole grains, for example, would resupply much if not all of the thiamine which was required to metabolize it.

Fever, hyperthyroidism, liver disorders, and diseases which interfere with digestion and metabolism can also raise thiamine requirements. You can get a thiamine deficiency in the hospital from the heavy carbohydrate load of the intravenous feeding. Food high in tannin, or tannic acid, can cause a thiamine deficiency. Tannin, which is present in large quantities in tea and betel nuts, destroys thiamine in the body. Vitamin C partially inhibits and reverses the destruction, however. In one study, human volunteers drinking tea along with a normal diet exhibited both biochemical and clinical symptoms of thiamine deficiency.  A quart of tea destroys about twice the RDA of thiamine.  Coffee also destroys thiamine in the body. A quart of coffee consumed over a three-hour period was shown to destroy most of the body's store of thiamine. (The villain in coffee is not tannin, or even caffeine, but chlorogenic acid.) Women using oral contraceptives are in danger of a thiamine deficiency, too. In one study, at least three mg. daily of extra thiamine was necessary to make up for the deficiency caused by the oral contraceptives.

Older women may need more thiamine just to maintain adequate levels in their bodies. Older women have been shown to excrete less thiamine than younger women on similar diets. The implication of this is that the older women were using more than the younger women, or at least they needed more thiamine to maintain adequate levels of vitamin activity in their bodies. When the women were placed on thiamine-deficient diets for a while, and then put back on adequate diets, the older women took longer to recover from the effects of the deficiency. Athletes, because they consume and expend more energy, obviously would be at risk for a thiamine deficiency. Such deficiencies have been reported. People with chronic liver disease, both alcoholics and nonalcoholics, have been reported deficient in thiamine, and should receive more than the RDA.

Where is it found ?

Thiamine is available in supplemental form in a wide range of dosages, from one mg. all the way up to hundreds of milligrams. Thiamine is nontoxic, and allergic intolerance is rare. Doses as high as 500 mg. per day have been given for periods up to a month with no signs of toxicity. The richest natural sources of thiamine are organ meats such as liver, heart, and kidney. Yeast, lean meat, eggs, green leafy vegetables, whole grain cereals, nuts, berries, and legumes are also good sources. White rice and flour have been rendered void of thiamine by processing, but small amounts are "fortified" back. Thiamine is water-soluble and destroyed by oxidation. Cooking in water contributes to thiamine loss when the vitamin dissolves in the water and becomes vulnerable to oxidation.

Who is likely to be deficient ?

Deficiency is most commonly found in alcoholics, people with malabsorption conditions, and those eating a very poor diet.

How much to take

While ideal levels are somewhat uncertain, one study reports that the healthiest people eat more than 9 mg per day. The amount found in many multivitamin supplements (20 to 25 mg) is more than adequate.

Vitamin B1 is nontoxic, even in very high amounts.

Vitamin B1 works hand in hand with vitamin B2 and B3. Therefore, nutritionists usually suggest that vitamin B1 be taken as part of a B complex vitamin or other multivitamin supplement.

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