CHAPTER XIV 

 THE NUTRITIONAL VALUE OF FATS 



1. Introduction 



Fat fulfills a number of functions in the animal organism. Until re- 

 cently, it was generally considered that these functions were non-essential, 

 since they could be carried out by other foodstuffs. It has now become 

 evident that fats play a unicjue role in many respects. Fats must there- 

 fore be considered as essential components of the diet rather than as only 

 optional factors. 



One of the roles which fat plays is as a carrier of fat-soluble vitamins. 

 Fats also assist in the absorption of these compounds from the gastro- 

 intestinal tract, even though they may not themselves contain the vita- 

 mins. A number of years ago Evans and Lepko^^sky^ demonstrated that 

 fats exert a marked sparing action on the antineuritic vitamin B (thiamine). 

 Furthermore, fats are important in the diet in that they improve palat- 

 ability. Low-fat diets prove extremely unappetizing, and their use is 

 often associated with a voluntary reduction in food consumption. Ac- 

 cording to Starling,- the civilian population in Great Britain lost weight 

 during World War I partly as a result of the failure to consume as great 

 a number of Calories on the high-carbohydrate, low-fat diet as were needed 

 to maintain a caloric equilibrium. Fats also serve as important adjuncts 

 in the preparation of many baked foods. Finally, it is well known that 

 fats have the highest caloric density of any of the common foodstuffs. 

 Each gram of fat yields 9.3 calories (1 Kilo calorie equals 1,000 Calories), 

 whereas proteins and carbohydrates yield only 4.1 Calories per gram under 

 similar conditions.^ Since fats are hydrophobic, they are usually laid 

 down in the tissues without additional water. On the other hand, pro- 

 teins and carbohydrates are usually associated with considerable amounts 

 of water. For this reason the ratio of the caloric content of fatty foods 

 and of non -fatty foods is usually greater than 2.3: 1, which is the ratio of 

 the caloric density of dry fats to that of carbohj^drates and proteins. 



' H. M. Evans and S. Lepkovsky, /. Biol. Chem., 83, 269-287 (1929). 

 2 E. H. Starling, Brit. Med. J., II, Part I, 105-107 (1918). 



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