The vitamin B complex consists of many different types of chemical compounds necessary for many vital bio-chemical processes in the body. The vitamin B1 or thiamine is one of the vital co-enzymes that plays a vital role in the processes involved in production of metabolic energy. One major function of the vitamin B1 or thiamine is its role as part of a co-enzyme system enabling the metabolism of carbohydrates. The vitamin B1 can be thought of as being the spark plugs which maintain energy producing processes in the body and keeps them running. The excitation of nervous tissue is another role played by thiamine aside from its other enzymatic functions elsewhere in the human body.
Thiamine deficiency is linked to a classic syndrome called beriberi - the first deficiency disease identified for this vitamin. Beriberi is present in many different forms; some of the manifestations include dry beriberi, where the main symptoms can sometimes include muscular atrophy and inflammation of the nerve endings. In the form of disorder called wet beriberi, there is general edema and internal effusions that can at times be complicated by myocardial insufficiency in the affected individual. The third type is called infantile beriberi; this form of beriberi is a complex combination of the symptoms of the wet and dry beriberi.
Protein synthesis in the brain and organs is depressed by a deficiency of thiamine deficiency - the uptake of two essential neurotransmitters in the brain is also suppressed, these two chemicals are acetylcholine and serotonin, they are used by nerve synapses in the brain for the transmission of nerve signals. The transmission of nerve impulses is impaired without adequate levels of these chemicals.
The complete disruption of the bio-chemical mechanisms controlling appetite is another effect of a thiamine deficiency, the person suffering the deficiency loses all desire for food. The inhibition of carbohydrate metabolism due to the deficiency is connected to this suppression of the appetite. The loss of appetite can be understood as an analogy - when the "engine" is stalled or sputters, the necessity for more fuel may die with it.
One of the most severe results of a thiamine deficiency is the reduction in the synthesis of major cellular antibodies; these compounds form a very important part of the body's immune system and the disruption of their production results in an increased susceptibility to diseases and pathogens.
Nervous exhaustion is the first apparent symptom that the demand of thiamine in the body has exceeded the supply from the dietary sources - a condition termed neurasthenia in the clinical lingo. Thiamine deficiency causes suppression of the appetite, weakens the person, affects the memory and kills initiative; it also affects concentration and temperament in uncertain ways. A persistent state of physical fatigue and depression starts to affect the person. Physical symptoms such as severe abdominal pains and chest pain ensue. Burning sensations in the feet and the "pins and needles" effect begins to affect the toes. The degeneration of the nerve pathways is what is causing these problems. The muscles are affected after the degeneration of the nerves. With the exception of a persistent tenderness in certain muscles in the legs, the general sense of touch seems to fade away slowly. The process of walking about becomes more than a chore and the person must strain a lot just to move from one place to another. The cardiac muscles are affected next and begin to deteriorate.
The disorder of beriberi has been known for thousands of years, however, the reason behind the condition was not properly investigated till the last half of the nineteenth century - at any rate the disease was primarily a disorder that affected rich people. Many of the B vitamin deficiencies affected mainly rich upper class people before they began to affect the poorer classes even though we normally don't relate nutritional deficiencies with rich people. A primary reason for beriberi affecting only the rich early on, was that only very rich people could afford the consumption of refined foods such as white polished rice and flour till the very end of the nineteenth century - an era of great economic inequality. Only at the turn of the 20th century did the milling of grain become cheap and universal. As polished rice and wheat became the basic item of food for millions of people, beriberi began to spread to the lower classes. Polished rice and wheat has almost no content of thiamine when compared to brown rice - as economic prosperity began to spread, the beriberi assumed the mantle of a disease affecting the entire population at large.
Two factors control the body's requirement for thiamine at any one time - one is the high caloric content of the diet, with respect to dietary carbohydrates in particular, the other factor is the amount of energy expended by the person at any one time. The main point being that a person eating very little carbohydrate and not expending energy will require less thiamine than somebody who eats a high carbohydrate diet all the time and expends a lot of energy. The human body also requires some trace amount of thiamine, an essential requirement for thiamine, which even the most sedentary person who does not eat must consume in the diet. The RDA of thiamine is one mg per person. The RDA is really set at about 0.5 mg of the vitamin for every 1000 calories taken in the daily diet.
Many other factors can come into play and raise the body's requirement of thiamine at any one time. Thiamine is required in higher amounts by pregnant and lactating women. A thiamine deficiency also tends to affect alcoholics - who are at a greater risk of developing such a deficiency. The metabolism of alcohol is similar to carbohydrates; it thus uses up the store of B vitamins in the body without replacing them at the same time. For example, a lot of thiamine would be supplied by an equal caloric load of whole grains when it is metabolized, the thiamine supplied would almost equal the amount it burns in the body during the metabolic process - this does not occur with alcohol.
The requirements for thiamine in the body can also be raised by problems like fever, disorders such as hyperthyroidism, all sorts of liver disorders and different diseases that can interfere with the digestion and metabolism of vitamins. The heavy carbohydrate load of intravenous liquid foods can cause some people to develop a thiamine deficiency during a long stay in the hospital. A thiamine deficiency can also be induced by the consumption of food that have a high tannin content, or those foods that are high in tannic acid. The plant pigment tannin is found in very large quantities in tea leaves and in betel nuts, this pigment can destroy and degrade the thiamine already present in the body of the person. The destruction of thiamine and its degradation is partially inhibited and reversed by the action of vitamin C. Biochemical and clinical symptoms of a thiamine deficiency were experienced by volunteers who were given tea along with a normal diet during one study that tested the effect of tannin on thiamine. About two times the RDA of thiamine can be destroyed and degraded by the consumption of just a quart of tea. Thiamine is also degraded within the human body by the actions of the alkaloid caffeine found in coffee. Most of the body's store of thiamine was found to be degraded by just a quart of coffee drunk over a period of three hours. The main culprit that degrades thiamine found in coffee is not tannin, or even caffeine, but the compound known as chlorogenic acid. A thiamine deficiency is also likely to affect women who make extensive use of oral contraceptives. The deficiency induced by oral contraceptives was the subject of one study, where it was found that a minimum 3 mg a day of extra thiamine was needed to correct the deficiency induced by long term use of oral contraceptive pills.
The levels of thiamine required by older women just for maintaining adequate levels of the vitamin in the body is greater than what is normally required by younger women. When compared with younger women on similar diets, the older women generally excrete less thiamine than the younger women. One major lesson from this observation is that thiamine was used at a faster rate by older women, it can also be said that such women require more thiamine in the diet just to maintain adequate levels of the vitamin activity in their body at any one time. Older women also took far longer to recover from a deficiency of thiamine than did young women when the different age groups of women were placed on diets deficient in thiamine for a while and then returned to well balanced diets. Thiamine deficiency is also likely to affect athletes, as they tend to consume more food and expend much more energy than the average person. Athletes suffering from such deficiencies have been reported in clinical journals. A deficiency of thiamine has also been reported in people who are affected by chronic liver disease, thiamine deficiency tends to affect both alcoholics and non-alcoholics equally but is much more prevalent in alcoholics with liver problems - such people should receive thiamine in doses above the RDA to correct this imbalance in the body.
Supplements of thiamine and different forms of the vitamin are available in a large range of dosages, starting from one mg going all the way up to hundreds of milligrams. Allergic intolerance to thiamine is rare and thiamine is not toxic. No signs of toxicity are reported even after people received doses as high as 500 mg daily, for periods lasting up to a month at a time. Thiamine is found in the highest quantities in natural sources of thiamine such as organ meats - including the kidneys, the liver, the heart and the pancreas. Other good sources of thiamine are yeast, lean meats, eggs and all kinds of green leafy vegetables, all kinds of whole grain cereals, nuts and berries and all legumes such as beans and peas. Thiamine is almost eliminated from most white rice and flour during the processing of grains, however, trace amounts are often "fortified" back into the grains. Oxidation destroys thiamine in the body and this vitamin is also soluble in water - hence, rice and other grains must not be washed too thoroughly before being cooked. Thiamine loss occurs when cooking is done in a lot of water as the vitamin easily dissolves in the water and can then become a prime target for oxidation reaction.
Alcoholics in general are most likely to suffer from a thiamine deficiency; such a deficiency is also likely to affect people suffering from malabsorption disorders and on a diet poor in nutrient content.
A single study reports that the healthiest individuals consume more than nine mg of thiamine daily; however, the ideal levels are still unknown. For the average person, the amount of thiamine present in many multi-vitamin supplements - at 20 to 25 mg doses is more than sufficient.
Even when it is consumed in high amounts, the vitamin B1 does not cause toxic effects in the body.
The functions of the vitamin B2 and B3 are combined with the function of thiamine in the body. This is the reason, that most nutritionists will suggest supplements of vitamin B1 be taken as part of a B-complex vitamin or other multi-vitamin supplement.