Vegetable sources – Cereals (in the husk and embryo), pulses, nuts and green vegetables, i.e. beets, carrots, turnip, lettuce, cauliflower, peers, beans, etc are rich sources. Polished rice and white flour are poor in this vitamin content. Animal sources – generally poor. Yeast and egg –yolk contain fair amount (100i.u.). Milk is an important source of thiamine for infants, provided the thiamine content of their mothers is satisfactory.
The main source of vitamin B1 in the diet of Indian people is cereals (rice and wheat), which contribute from 60-85 percent of the total supply. The thiamine content of selected foodstuff is given below:
Foods of vegetable origin
Foods of animal origin
Rice, raw home pounded
Bengal gram dhal
Free thiamine is absorbed readily from the small intestine. It is much stored in the body. About 25% of the ingested vitamin B 1 is excreted in the urine. It has also been produced synthetically.
Thiamine is readily lost from rice during the process of milling. Being a water-soluble vitamin, further losses take place during washing and cooking of rice. Much of thiamine in fruits and vegetables is generally lost during prolonged storage. Thiamine is also destroyed in toast and in cereals cooked with baking soda.
Benefits of vitamin B1
Thiamin increases the blood circulation, helps in the blood formation and the metabolism of carbohydrates. It is also required for the health of the nervous system and is used in the biosynthesis of a number of cell constituents, including the neurotransmitter acetylcholine and gamma-amino butyric acid (GABA). It is used in the formation of hydrochloric acid, and therefore plays a part in digestion.
It is also great for the brain and may help with depression and assist with memory and learning. In children it is required for growth and has shown some indication to assist in arthritis, cataracts as well as infertility.
In the absence of this vitamin, pyruvic and lactic acids fails to be broken down, and hence, accumulate in blood and tissues. Most of the deficiency signs are due to the abnormal accumulation of these acids. It also helps the enzyme system, which is responsible for the synthesis of fats from carbohydrates and proteins.
Without thiamine, the cells cannot utilize oxygen or fuel for energy. The nervous system cannot function properly without thiamine, nor can the muscles perform at their best.
About 1.8 mgm for a diet producing 3.000 calories. The requirement is increased in pregnancy, lactation, heavy muscular work, high carbohydrate diet etc. daily intake for children range from 0.4 mgm for infants to 1.3 mgm for pre-adolescents. Requirement of thiamine increases in shock, haemorrhage, serious illness or injury, during oral administration of antibiotics etc.
The two principal deficiency diseases are beriberi and Wernick’s encephalopathy. Beriberi may occur in three main forms:
- The dry form characterized by nerve involvement (peripheral neuritis)
- The wet form characterized by heart involvement (cardiac beriberi)
- Infantile beriberi, seen in infants between 2 and 4 months of age. The affected baby is usually breast fed by a thiamine deficient mother who commonly shows signs of peripheral neuropathy.
The general symptoms in beriberi are as follows:
- There is oedema especially in legs.
- Loss of appetite, atony of the gastrointestinal tract, hypochlorhydria. All these are due to lack of energy derived from the imperfect metabolism of carbohydrate.
- Lactic and pyruvic acids accumulate in blood.
- In polyneuritis there is tenderness of muscles of feet and legs, ataxia and muscular weakness, is a characteristic feature. These defects are due to diminished utilization of carbohydrates and production of energy. Pyruvic acid accumulates in the brain stem, brain and cerebrospinal fluid.
- Heart also becomes weak and enlarged, due to accumulation of pyruvic acid. Cardiac failure may also occur in some subjects.
- Cerebral beriberi has also been reported. In this disease the gray matter of the cerebrum round the third ventricle is affected. When thiamine is absent from the diet, all kinds of muscle pains develop over the body. The nerves become irritable, and the individual suffers from weakness, anaemia and lack of appetite.
Wernick’s encephalopathy (seen often in alcoholics) is characterized by ophthalmoplegia, polyneuritis, ataxia and mental deterioration. It occurs in people who fast.
Toxicity and symptoms of high intake
Thiamin toxicity is uncommon; as excesses are readily excreted, although long-term supplementation of amounts larger than 3 grams have been known to cause toxicity.
Who need more
People who take alcohol, antacids and birth control pills or patients who have taken hormone replacement therapy, need more thiamine in their diet. People suffering from depression or anxiety and those passing large volumes of urine, or suffering from an infection may all require more thiamin.
It is thought that thiamin can be useful for motion sickness in air and sea travel, and that this vitamin also repels insects when excreted through the skin.