82 



OUR FOOD SUPPLY 



blood. They are present in fruits, vegetables, and 

 milk; we also take minerals more directly in salt. 



Chemical analysis shows that the human body is 

 more than 65 per cent water. Water carries dissolved 

 foods in the body and is necessary for the removal 

 of waste matter. Although fruits, vegetables, and milk 

 contain large quantities of water we need to drink 

 additional amounts. The amount needed depends 

 largely upon climate and occupation. In warm weath- 

 er we need to drink more than in cold weather be- 

 cause evaporation of water is going on faster from 

 the surface of our bodies. We should always drink 

 plenty of water, for there is no danger that we shall 

 drink too much. Many physicians recommend at least 

 six glasses a day. 



What is the work of vitamins? Vitamins are sub- 

 stances that help to regulate physical growth and 

 health. Scientists have not yet been able to deter- 

 mine the exact chemical nature of them, but their 



VITAMIN "E" 

 Prttiantl SitriUly 



FIG. 123. FOODS RICH IN VITAMINS 



sources are known and also the effects they produce 

 in the body. They are named by letters of the alpha- 

 bet. 



Recent experiments seem to indicate that vitamins 

 are in some way built up in the leaves of green plants. 

 They are found in such foods as milk, butter, and 

 eggs because cows and chickens are fed on foods de- 

 rived from plants which contain vitamins. 



Vitamins A and D are quite abundant in milk, 

 butter, yolk of eggs, and cod-liver oil. Vitamin A is 

 present also in green vegetables. Vitamin A is known 

 to help in the development of the eyes and to keep 

 them free from diseases. Vitamin D prevents rickets. 

 This is a disease in which the bones of growing chil- 

 dren soften. The ultra-violet rays of sunlight have the 



same effect as the vitamin on children, and because 

 of this fact vitamin D has lately been called the sun- 

 shine vitamin. Science has learned recently how to 

 establish vitamin D in foods artificially by means 

 of ultra-violet rays. Several foods, including milk, 

 treated by this process have appeared on the market 

 recently. 



Recently it has been found possible to produce vita- 

 min D artificially in the human body by means of 



U. S. Bureau of Home Economics 



FIG. 124. VALUES OF VITAMINS IN ANIMAL DIET 



Illustrations on the left show effect of lack of vitamins ; illus- 

 trations 'on the right show individuals from the same broods 

 that have had sufficient vitamins. 

 Upper vitamin D; middle, vitamin A; lower, vitamin B. 



ultra-violet light rays. These rays are abundant in 

 sunshine and are mostly responsible for sunburn and 

 tan. Investigations have revealed that native South 

 American children who have lived in the open scantily 

 clothed do not suffer from the calcium deficiency 

 which results from too little of vitamin D. 



This discovery has made possible the treatment of 

 rickets by the use of arc lamps and mercury vapor 

 lamps which are highly productive of the ultra-violet 



