Relation of Dietary Fat to Riboflavin Requirement of Growing Rats. ∗

Abstract

Studies in this laboratory on the relation of the level of fat, carbohydrate, and protein in the diet to the vitamin requirements of growing animals led to the observation that the feeding of high levels of fat to young rats increased the riboflavin requirement. Modifications of the basal riboflavin-low ration K₂₁ described by Wagner, Axelrod, Lipton, and Elvehjem 1 were utilized in studying this effect. Lard was isodynamically substituted for dextrin at two levels so that in ration K₂₂ the total fat content was about 25% and in K₂₃ about 40%. Choline was added to the extent of 5 mg per 100 g of K₂₁, or its isocaloric equivalent in the other rations. Storage of the rations in the refrigerator and daily feeding prevented rancidity.

In the first series albino rats weighing from 60 to 75 g were partially depleted of their riboflavin reserves by placing 12 rats on each of the above rations for a period of 4 weeks. Four animals in each group were then supplemented with 3γ of riboflavin per day, four, with 6γ of riboflavin, and four were continued on the basal ration with no additional supplements. The growth responses of typical animals are illustrated in Fig. 1.

The growth curves show that the feeding of high levels of fat to growing rats increases the requirement for riboflavin and that the higher the fat level, the more noticeable is the effect. The greater loss of hair and extent of dermatitis observed in the rats raised on the high fat diets were even more notable than the weight differences. Rats maintained in a chronic state of deficiency on the high fat rations developed a spastic gait due to a paralytic condition of the hind legs.