Vitamin B1 is also known as thiamine belongs to water-soluble vitamins of B complex. In the human body about 80% of thiamin are presented in the form of thiamin diphosphate (TDP). Another common name for thiamin diphosphate is thiamin pyrophosphate (TPP).
Function of vitamin B1 in the human body
An active form of vitamin B1, thiamine pyrophosphate, participates in several enzymatic reactions related to the metabolism of carbohydrates, the branched-chain amino acids (isoleucine, leucine, valine) and fatty acids.
Thiamin diphosphate requires for its synthesis availability of magnesium, adenosine triphosphate (ATP), and the enzyme, thiamin pyrophosphokinase.
Thiamine plays different roles. It can act not only as a coenzyme.
As the coenzyme, thiamine pyrophosphate involved in:
1. The conversion of energy;
2. Synthesis of pentoses and nicotinamide adenine dinucleotide phosphate (NADPH)
In another capacity, namely as not coenzyme, thiamin assists in conducting of the nerve impulse.
As a coenzyme, when converting the energy, vitamin B1 in the form of thiamine pyrophosphate takes part in such multi-enzyme complexes as the pyruvate dehydrogenase complex, the alpha-ketoglutarate dehydrogenase complex, and the branched-chain a-keto acid dehydrogenase complex (leucine, isoleucine, and valine).
As a coenzyme, thiamin pyrophosphate helps in the conversion of pyruvate into acetyl CoA. This is a crucial step that allows the carbohydrates to enter the citric acid cycle (Krebs cycle) for making of much more ATP than during glycolysis. In the tricarboxylic acid cycle (Krebs cycle), TPP helps convert carbohydrates from 5-carbon to 4-carbon carbohydrates.
Due to the fact that muscles require a lot of ATPs for their functioning, half of the thiamin in the body is stored in the skeletal muscles.
As a coenzyme, thiamine pyrophosphate also works with transketolase – a key cytoplasmic enzyme in the pentose phosphate pathway. The pentose phosphate pathway is vital for the forming of pentoses that are involved in the synthesis of nucleic acids and nicotinamide (NADPH).
About 10% of vitamin B1 in the body is represented as thiamin triphosphate (TTP). In this form, the thiamine is needed in the activation of ion transport in nerve cells and may be involved in neurotransmission by regulating sodium channels and acetylcholine receptors.
Signs and symptoms of thiamine deficiency
One of the first symptoms of thiamine deficiency is a loss of appetite (anorexia). Other symptoms of deficiency - a muscle wasting, weight loss, cardiovascular problems.
Thiamine deficiency affects almost all body systems, including the cardiovascular, nervous, muscular system and the gastrointestinal tract.
People for whom the energy source are foods and beverages with the so-called empty calories (white bread, fast food, soda), are at risk for insufficient intake of thiamine. Thiamine deficiency is often associated with alcoholism.
With a shortage of vitamin B1, the thiamin deficiency disease develops wich is known as beriberi. It is associated with severe deficiency of thiamine. This disease has an impact on many organs and body systems, including the central and peripheral nervous system.
Beriberi is divided into "dry beriberi" and "wet beriberi".
Dry beriberi is characterized by damage to the nervous system and muscle weakness in the hands and feet.
In wet beriberi, the cardiovascular system is damaged. It is characterized by enlargement of blood vessels, which leads to excessive load on the heart and kidneys. Kidneys have to work harder to retain salt and water. This, in turn, leads to edema.
Typically, both types of beriberi appear together, despite the fact that one of the sets of symptoms predominates.
How much vitamin B1 should i take daily
The Recommended Dietary Allowance (RDA) for adults is 1.2 mg / day for men and 1.1 mg / day for women.
The optimal dose - 5-15 mg.
Table of recommended daily allowance (RDA) of vitamin B1 intake in mg
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What foods have thiamin
Most foods contain some amount of thiamine.
Nutritious foods rich in thiamine are oatmeal, flax and sunflower seeds, brown rice, whole grain rye, asparagus, cabbage, cauliflower, potatoes, oranges, beef liver, pork and chicken, and eggs. Yeast, wheat germ, and soybean milk also contain significant amounts of vitamin B1.
Prolonged cooking destroys thiamine. Like other water-soluble vitamins, thiamine goes into the water in which products are blanched or boiled. Cooking methods that require little or no water, such as steaming and microwaving retain thiamine as well as other water-soluble vitamins.
Other factors, which may prevent entry thiamin into the body, are the presence of certain substances in the diet, such as thiaminases and polyhydroxyphenols.
Thiaminases can be found in the raw fish. They are heat-labile and therefore cooking inactivates thiaminases.
Polyhydroxyphenols (tannic and caffeic acid) are thermally stable and are contained in coffee and tea, as well as in some fruits and vegetables such as blueberries, black currants, Brussels sprouts, red cabbage. They oxidize thiamine. This can be prevented by the presence of reducing compounds in the diet (vitamin C and citric acid).
The upper allowable level of consumption of thiamine
To date, a tolerable upper intake level (UL) for thiamine is not set , because there are no accurate toxic effects from the consumption of excess thiamine when taking from food or on the basis of long-term oral supplementation (200 mg / day).
If you wish to receive more information about vitamins and their contents in a variety of products, follow the links on the References page.