The Effect of Fat Level of the Diet on General Nutrition

Abstract

Weanling rats fed a diet containing vitamin-test casein as such, or casein after reprecipitation or exhaustive extraction, or both, as well as sucrose, cellu flour, a salt mixture, and the synthetic B vitamins, developed symptoms of fat deficiency in 12 weeks. The injection of the growth hormone in such fat-deficient rats did not result in growth but also did not cause death. In this respect the action of the growth hormone differs from that in vitamin A-deficient rats. When 20 mg of linoleic acid were given as a supplement to the fat-deficient rats, a prompt response in growth resulted, which was not further augmented when the level was increased to 60 mg per day. The injection of the growth hormone combined with the feeding of methyl linoleate to fat-deficient rats resulted in an immediate growth response, in contrast to the more tardy action of the linoleate alone. Although the average body weight of the growth hormone-treated, linoleate-fed rats exceeded that of the animals receiving only the linoleate, the growth curves remained parallel throughout the test. The administration of a 10% cottonseed oil diet to rats receiving linoleate at an optimum level resulted in further acceleration of growth. This may indicate that the oil possesses some effect other than that of linoleic acid; perhaps the results were dependent on an additive effect of other unsaturated acids or of fat itself.