152 BIOLOGICAL CHEMISTRY 



Accessory Food Substances. When, however, purified food 

 substances are fed to animals they do not thrive, and it has 

 been proved that there are unknown substances which are 

 required in minimal amounts. These substances are independ- 

 ent of the energy value of the food, but they are found in 

 various fresh natural food substances.* 



The absence of these accessory substances is associated 

 with certain diseases, and at least three accessory substances 

 are required. They are known only by their properties, i.e. 

 by the effect of their absence from the diet. 



The classification is : 



Vitamin A found in certain fats and green leaves. 



Vitamin B found in the pericarp and germ of cereals, in 

 yeast, etc. | 



Vitamin C found in varying quantity in fresh uncooked 

 foods. 



The investigation of these substances is still in progress, 

 and the distribution of them in various kinds of food, the 

 effect of cooking and methods of preservation are being 

 examined. 



The fat-soluble A substance is probably destroyed by 

 heating and oxidation, f whilst the water-soluble B substance 

 is thermo-stable. The water-soluble substance C is known 

 to be thermolabile. 



Absence of fat -soluble A substance is probably a factor in 

 the production of rickets. 



Absence of water-soluble B substance causes paralysis, 

 or the disease beri-beri. 



And absence of water-soluble C substance causes scurvy. 



A relative deficiency of these substances may cause ill 

 health, even if the deficiency is not enough to cause the 

 characteristic symptoms of the diseases associated with their 

 absence from the diet 4 



* It may be that greater expenditure of energy may require a larger 

 supply of these substances. 



f F. G. Hopkins, J. C. Drummond and K. H. Coward and S. S. 

 Zilwa, Biochem. Journ., 1920, vol. 14, pp. 725, 734 and 740. 



{ Medical Research Committee Report on the Present State of 

 Knowledge Concerning Accessory Food Factors. 



