The Effect of Fat Level of the Diet on General Nutrition VI. The Interrelation of Linoleate and Linolenate in Supplying the Essential Fatty Acid Requirement in the Rat ,

Abstract

A sex difference in the requirement for linoleic acid has been found. The optimum dosage for male rats exceeds 50 mg daily, while that for female rats has been found to be between 10 and 20 mg per day. The requirement for male rats based on extrapolation data would appear to be 100 mg daily. Linolenic acid had only slight growth-promoting action when fed alone to fat-depleted rats at the level indicated. However, when fed with suboptimum doses of linoleic acid, the resultant activity of the additional linolenate equalled that of linoleate. It is suggested that a sparking action on the part of linoleate is required before linolenate can play its role as an essential acid. Greater growth was found in the female rats on 30% cotton-seed oil diets than could be obtained on a fat-low regime where the animals were supplemented with an optimum quantity of methyl linoleate. In the case of male rats, it would appear probable that the growth of animals on a fat-free regime might be raised to that of rats on a 30% fat diet if a sufficiently high amount of methyl linoleate were administered. The growth response of the male rats plotted against the log dose was a straight line function when linoleate in the range of 5 to 50 mg was administered. The possibility of using such a procedure for assay of the biopotency of substances containing essential fatty acids is discussed.