900 XIV. NUTRITIONAL VALUE OF FATS 



Since legislation removing the restrictions on colored margarine has been 

 passed, a number of brands have employed carotene both as a coloring 

 matter and as a source of part of the vitamin A. This provitamin A may 

 now be included as a portion of the vitamin A declared on the label, ac- 

 cording to the recent ruling of the U. S. Food and Drug Administration,-^^ 

 which stipulates that the oleomargarine must contain not less than L5,000 

 I.U./lb. Margarine has been reported to be an especially effective vehicle 

 for facilitating the utilization of /3-carotene in the rat.-'-^ 



(6) Vitamins D. Vitamin D is found only rarely in animal fats, and 

 never in vegetable fats. Small amounts of this vitamin may occur in 

 butter, depending to a considerable extent upon the diet of the cows from 

 which the butter is obtained. Some vegetable margarines are also fortified 

 with vitamin D. The most concentrated natural sources of vitamin D 

 (chiefly vitamin D3) are the fish-liver oils. The potencies of these various 

 liver oils vary from a comparatively low figure of 100 I.U./g. for cod- 

 liver oil {Gadus morrhua),^^ which was formerly considered to be an im- 

 portant source of vitamin D, to as high values as 40,000 I.U./g. for the 

 liver oil of the bluefin tuna (Thunnus thynnus), while the oil of many 

 fishes, such as the broadbill swordfish {Xiphias gladius) and the yellow- 

 fin tuna (Neothunnus macropterus) contains approximately 10,000 I.U./g. 

 Actually cod-liver oil, which was long regarded as the standard treatment 

 for rickets, holds twenty-third place, as regards the content of vitamin D, 

 in the values listed by Bills-*^ for various fish-liver oils. In addition to 

 the food sources of vitamin D, it can also be formed by the irradiation of 

 the provitamins D with ultraviolet light. This may either occur in the 

 skin of the animal or by irradiation of the foodstuffs in the course of their 

 preparation. As a result of this the irradiation of foods for the production 

 of vitamin D has become wide-spread, and the distribution of the D vita- 

 mins has been greatly extended. In cases in which vitamin D is required 

 in increased amounts, such as in infancy, one does not ordinarily depend 

 entirely upon dietary sources for the supply of this vitamin, but rather 

 resorts to the fish-liver oils or to preparations of irradiated ergosterol, 

 or even to direct irradiation of the body with sunlight or with ultraviolet 

 rays. Consequently, although the distribution of vitamin D in food fats 

 is of academic interest, it is not of too great importance in practical nu- 

 trition, because of the uncertainty of supply and because of the availa- 

 bility of much more concentrated sources of the material. 



286 J. L. Thurston, Federal Register, 17, No. 100, 4613-4615 (May 21, 1952). Food and 

 Drug Admin., Federal Security Agency, Part 45. 

 288 C. E. Bills, Physiol. Revs., 15, 1-97 (1935). 



