216 VITAMINS 



than bone, e.g., in the aorta, kidneys, S,nd intestines, the extremely potent 

 preparations of vitamin D should be used with care and preferably in 

 accordance with the advice of a competent physician. 



Requirements 



Because of the various factors that affect the individual's need for 

 vitamin D, it is difficult to determine exactly the required amount. The 

 Food and Nutrition Board of the National Research Council recommends 

 10 /Jig. per day for infants under one year and for women during lactation 

 and the latter half of pregnancy. This is equivalent to 400 I.U. since 

 0.025 fjLg,. provides one unit. Older children should also receive 10 [xg. 

 (400 units) daily, but adults probably require no vitamin D in tKe diet 

 unless they are seldom or never exposed to direct sunlight. This amount, 

 10/xg., would be contained in approximately 1-2 teaspoonfuls of cod- 

 liver oil, 2 lb. of butter, 2.5 gal. of whole milk, or 1 doz. eggs. It should 

 be emphasized that no ordinary diet can be relied upon to meet the require- 

 ments of a growing child for vitamin D unless special precautions are 

 taken to include adequate amounts of a fish-liver oil, or other suitable 

 source. 



One fortunate aspect of the problem of supplying adequate amounts 

 of vitamin D to growing children is that if more than the day's require- 

 ment is consumed at one time, the extra amount is stored in the body 

 (mostly in the liver) and prevents the development of any deficiency 

 for a correspondingly longer time. Thus a single dose of 20,000 I.U. 

 of vitamin D per kilogram of body weight was found to protect puppies 

 from rickets for as long as 12-14 months. 



This ability of vitamin D to be stored extensively in the body is also 

 shared by the other fat-soluble vitamins (A, E, and K), but not by 

 the water-soluble B vitamins or vitamin C. 



VITAMIN E 



Physiological function 



Because the outstanding function of vitamin E seems to be that of 

 promoting reproduction, it has become known as the "antisterility factor" 

 or "vitamin of reproduction." Such a term is somewhat misleading in 

 view of the fact that the vitamin performs other functions in the body, 

 including that of promoting growth. Moreover, it was noted previously 

 that vitamin A also is essential to reproduction. 



The most detailed investigations regarding the functions of vitamin E 

 have been carried out with rats. In the male rat on a diet deficient in 

 vitamin E the germ cells undergo a permanent degeneration, as evidenced 



