The Effect of Fat Level of the Diet on General Nutrition VIII. The Essential Fatty Acid Content of Margarines, Shortenings, Butters, and Cottonseed Oil as Determined by a New Biological Assay Method ,

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Abstract
A biological procedure for the determination of essential fatty acids has been established. Good agreement was obtained between the analyses for essential fatty acids by bioassay and by spectrophotometry in the case of margarine oils, butters, cottonseed oil, and a shortening prepared by selective hydrogenation. However, the bioassay procedure gave a result approximately twice as great as that obtained by spectrophotometric analysis with a shortening made by non-selective hydrogenation. The level of essential fatty acids in all samples of margarine was found to be higher than in the butter fats. Non-selective hydrogenation of cottonseed oil, the method employed in preparing baking shortenings, yields a product exhibiting a high amount of residual essential fatty acids, somewhat more than 4 times that noted for the same vegetable oil hydrogenated to the same iodine number but under selective conditions such as those employed in preparing frying shortenings. In confirmation of earlier work, it has been found that the administration of hydrogenated coconut oil has a depressing effect on the growth of rats fed a fat-low regimen, in proportion to the level fed; this depressing effect can be completely counteracted by adequate supplementation with linoleate. The optimum level of linoleate required by fat-depleted male rats would seem to exceed 200 mg per day. Apparently the requirement of essential fatty acids is increased with the concomitant ingestion of fat.