The members of this group are B complex vitamins and vitamin C. They are readily soluble in water.
The structure of vitamin B1 is given in Fig. 8.5.
Thiamine act as a coenzyme in the form of thiamine pyrophosphate in many enzyme systems. These are involved principally in the breakdown of glucose to yield energy.
Thiamine also aids in the formation of ribose, a sugar that is an essential constituent of DNA and RNA, the carriers of the genetic code. The adequate level of thiamine provides healthy nerves, a good mental outlook, a normal appetite and food digestion.
Meats, especially pork and liver are rich in thiamine and account for about one fourth of the average intake. Dry beans, peanuts and egg are good sources.
Whole grain breads and cereals supply about one third of the daily thiamine intake.
The requirement of thiamine depends on energy expenditure.
Infants - 0.3 - 0.5 mg / day
Children - 0.7 -1.2 mg / day
Adults - 1.2 - 1.5 mg/day
Pregnant women and lactating women - 1.3- 1.5 mg/day
Free thiamine is readily absorbed from the small intestine. Excess thiamine administered is not stored in the tissues. A part of the excess thiamine is excreted in urine and same of it is destroyed by the enzyme thiaminase.
The symptoms of thiamine deficiency occur because the tissue cells are unable to receive sufficient energy from glucose. Therefore, they cannot carry out their normal functions.
Early symptoms of thiamine deficiency include fatigue, irritability, depression and numbness of the leg and poor tone of the gastro intestinal tract together with constipation.
Beriberi, sometimes called “rice-eaters disease” is another deficiency symptom which is often seen in people whose chief diet is refined rice and is the most severe form of thiamine deficiency.