A New Dietary Deficiency With Highly Purified Diets. III. The Beneficial Effect of Fat in the Diet. ∗

Abstract

Some years ago Osborne and Mendel 1 reviewed the work which had been done on low fat diets, and from an experiment with 6 young male rats concluded that “if true fats are essential for nutrition during growth, the minimum necessary must be exceedingly small.” In view of the fact that their experimental animals were compared with the animals reared on a diet high in fat but low in protein, it seemed probable that both the controls and the experimental groups were subnormal, thus leaving the question unsettled.†

It has been observed in this laboratory that our lard free diet 316 (Table I) is uniformly inferior to the high fat diet 232. Recently a carefully controlled experiment has been conducted to compare diet 316 plus 2 drops of cod liver oil (Patch) daily with diet 232. The groups of 15 females were made up of littermate sisters. Each diet was supplemented by 0.7 gm. yeast (Fleischman) daily. Table II gives the average results. It will be seen that the performance on the 2 diets is very different, the animals on diet 316 being retarded in growth, sexual maturity and ovulation. In fact, the rate of ovulation is decreased to less than 50% of its normal value. (The growth, maturity and ovulation here recorded for animals on diet 232 is equal to the normal on natural foods.)

By the substitution of sucrose for starch and of pure casein for commercial casein, the fat content of the diet has been further reduced (starch has usually 0.5 to 0.6% non-extractable fat and commercial casein carries a variable amount of butter fat). While working with these purer and simpler diets (Diets 519, etc., Table I) it was found that by the addition of lard to the diet, ovulation was always somewhat improved and growth was markedly improved. (Table 111.) In fact, the animals which rxeived the high fat diet 522 may be considered about normal in weight and ovulation, while those on the fat free diet 519, are greatly stunted.