VITAMINS 



215 



following table. It will be noted that, except for vitamin D milk and 

 certain fish, most native foods contribute only negligible amounts of 

 this vitamin. 



Table 9-1 



Vitamin D content of foods 



(The values are expressed as micrograms of vitamin D per 100 g. of edible portion, 



fresh basis.) 



Food Vitamin D 



Egg yolk 4.6 



Halibut-liver oil 3500 



Lamb liver 0.43 



Mackerel 4-6 



Milk, whole 0.11 



Milk, vitamin D, irradiated. 1.1 

 Milk, vitamin D, fortified. . . 1.1 



Pork liver 1.1 



Salmon 12 



Sardines 6-8 



Spinach 0.005 



Tuna 5-8 



Veal liver 0.24 



Precursors of vitamin D are widely distributed in plant and animal 

 materials. Therefore, if a food is subjected for a few seconds to the 

 light from an ultraviolet lamp, it becomes potent as an antirachitic agent 

 through the conversion of its provitamin into vitamin D. Certain brands 

 of cereals, cookies, evaporated milk, yeast, and bread containing vitamin 

 D are now commercially available. In some cases the potency is due 

 to the addition of small amounts of irradiated ergosterol rather than to 

 irradiation of the food. 



Since foodstuffs can be rendered antirachitic through treatment with 

 light from an ultraviolet lamp, one might assume that plant products 

 would possess considerable potency as a result of the effect of the ultra- 

 violet rays of the sun. Such has not been found to be true. At least 

 by the time foods are prepared for consumption little, if any, vitamin 

 D is present. 



In addition to the fish-liver oils and foods that contain the D vitamins, 

 extremely potent preparations such as (1) liver oils fortified with addi- 

 tional vitamin D, (2) Hver oil concentrates, (3) calciferol dissolved in 

 an inert substance such as corn oil are on the market. Viosterol is a 

 general name for preparations of irradiated ergosterol. Cod-liver oil 

 contains on the average about 250 /^g. per 100 g., a concentration which 

 is exceeded by the liver oils of a number of other species. Thus halibut- 

 liver oil is 10-20 times richer, and the liver oil of one species of tuna 

 fish has been reported to contain 150,000 iJ.g. per 100 g. Since with 

 massive doses of vitamin D, calcification may occur in tissues other 



