60 THE INDIVIDUAL ORGANISM 



some green, leafy vegetables. In rats a deficiency of this vitamin causes sterility 

 due to degeneration of the sperm-producing tissues of the male and to abnormal 

 development and intra-uterine death of embryos in the female. Most of the 

 effects seem to be traceable to the action of vitamin E as an antioxidant; in its 

 absence carotene and vitamin A are rapidly destroyed both in the digestive tract 

 and in tissues. There is no reliable evidence that vitamin E is indispensable in 

 man, but it seems likely that it is required by all mammals. Attempts to use it 

 therapeutically have thus far been disappointing. 



THE WATER-SOLUBLE VITAMINS 



The original vitamin B is now known to have been a complex of at least 12 

 distinct vitamins. Three of these are known to be essential in human nutrition, 

 and some of the others may prove to be so. 



Vitamin B L (the antineuritic vitamin, thiamine, Ci 2 Hi 7 NjOSC1) is perhaps 

 the most important member of the B complex. It is abundant in the germ and 

 outer layers of seeds and also occurs in nuts, legumes, most vegetables, eggs, pork, 

 liver, and the tissues of many animals. In the form of thiamine chloride it is now- 

 made synthetically. Thiamine deficiency is the most prevalent vitamin lack among 

 human beings. Though required in only small amounts, it must be continually 

 taken into the body, since little of it is stored; any excess is excreted via the skin 

 and the kidneys. 



The importance of thiamine lies in its relation to carbohydrate metabolism. 

 In the form of diphosphothiamine it acts as a coenzyme with a carboxylase 

 enzyme to release energy from glucose. By their combined action these two 

 enzymes convert glucose to pyruvic acid and the latter to water and carbon 

 dioxide, with liberation of energy. When thiamine is lacking or inadequate in 

 amount, the reaction is not completed, pyruvic acid accumulates, and the full 

 energy value of the glucose is not obtained. This relationship explains the fact 

 that the thiamine requirement of the human body is not fixed but increases with 

 the consumption of carbohydrate foods. It has been found that the daily human 

 need of thiamine in micrograms may be expressed as equal to 0.00213 X weight 

 in pounds X Calorie intake. For a 150- pound man eating 2400 Calories of food a 

 day this totals 767 micrograms, and for such an individual 1,200 micrograms per 

 day would allow a reasonable margin of safety. 



Pronounced thiamine deficiency results in the disease called beriberi; lesser 

 deficiencies are manifested in a variety of symptoms, mostly involving the nervous 

 system. Prominent among such symptoms are neuritis, resulting from nerve 

 lesions and damage to the finer structure of nerves, loss of appetite, circulatory 

 disturbances and malfunctioning of the heart, and neurasthenic symptoms such 

 as easy tiring, weakness, head pressures, poor sleep, tenseness, irritability, unde- 

 fined aches and pains, and inability to concentrate. In so far as these symptoms 

 are the result of thiamine deficiency, they disappear promptly under administra- 

 tion of sufficient (often large) amounts of this vitamin. One of the earliest symp- 

 toms of lack of thiamine is the tendency of arms and legs to "go to sleep" from 

 poor circulation, especially during the night. Thiamine deficiency is one of the 

 easiest to recognize and correct. 



