Thiamine (vitamin B1) is a water-soluble vitamin. It is essential for the utilization of carbohydrates. Thiamine pyrophosphate (TPP), the coenzyme of cocarboxylase plays a part in activating transketolase, and enzyme involved in the direct oxidative pathway for glucose. In thiamine deficiency, there is accumulation of pyruvic and lactic acids in the tissues and body fluids.

Sources: Thiamine occurs in all natural foods, although in smell amounts. Important sources are: whole grain cereals, wheat germ, yeast pulses, oilseeds and nuts, especially groundnut. Meat, fish, eggs, vegetables and fruits contain smaller amounts. Milk is an important source of thiamine for infants, provided the thiamine status of their mothers is satisfactory. The main source of thiamine in the diet of Indian people is cereals (rich and wheat), which contribute from 60-85 percent of the total supply.

Recommended allowances: Daily requirement of thiamine is 0.5 mg per 1000 kcals of energy intake. The body content of thiamine is placed at 30 mg, and if more than this is given it is merely lost in the urine.

Deficiency: The two principal deficiency diseases are beriberi and Wernick's encephalopathy. Beriberi may occur in three main forms:

The dry form characterized by heart involvement (cardiac beriberi) and infantile beriberi, seen in infants between 2 and 4 months of live. The affected baby is usually breast-fed by a thiamine-deficient mother who commonly shows signs of peripheral neuropathy. Wernick's encephalopathy (seen often in alcoholics) is characterized by ophthalmolegia, polyneuritis, ataxia and mental deterioration. It occurs occasionally in people who fast.

A few short decades ago, frank cases of beriberi used to be frequently seen in the coastal districts of Andhra Pradesh where people eat highly polished rice. Recent investigations by the ICMR showed that such cases are now rarely encountered because of improved socio-economic conditions and diversification, in the diet consumed now. However, manifestations of minor degrees of thiamine deficiency such as loss of appetite, absence of ankle and knee jerks, and presence of calf tenderness have been frequently encountered in nutrition surveys indicating that the disease remains endemic in a moderate or mild from among certain sections of the population. In the Western countries, beriberi does occur occasionally, and is most commonly due to excessive alcohol consumption.

Thiamine losses: 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. This is the basis for advising people to eschew highly polished rice and eat parboiled or under-milled 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. The occurrence of absence of beriberi is determined by the local customs and cultural practices concerning the processing and cooking of rice and other foodstuffs.