THE NORMAL DIET OF MAN 701 



exists on a lower metabolic level. It is a notable fact" that during the 

 shortage of fat in this country in 1918 there was no appreciable increase 

 in the consumption of cereals. It was easier to live on the stored-up fat of 

 the body than to adopt a stuffing process with carbohydrates. 



In the third place, it seems that carbohydrates are more subject to 

 fermentative changes in the intestines than fats. Overloading the intestines 

 with carbohydrates in many individuals leads to abnormal fermentation, 

 the production of gases,, and general discomfort. We may conclude then 

 that, although man can dispense with fat provided he receives a full diet 

 of proteins and carbohydrates with the proper accessory substances, yet 

 to develop his full efficiency as a working machine, fat is an essential 

 ingredient of his diet and should furnish not less than 20 to 25 per cent, of 

 the total energy of his food. 



The significance of Meat. Butcher's meat, according to the cut, contains from 15 to 

 20 per cent, protein, and from 15 to 30 per cent. fat. Its importance in the dietary is 

 greater in northern latitudes, depending in part on questions of supply and of racial 

 habit. A diet rich in meat is a diet rich in animal protein and fat, and the protein 

 of such a diet will be considerably more than is required for the mere repair of 

 tissue waste. Under these conditions the fate of proteins in the body is somewhat 

 different to that of the other foods, viz. fats and carbohydrates. These other foods 

 are either stored up in the body in the form of fat, if in excess, or they are burnt up 

 in proportion to the needs of the working tissues. Proteins however, unless there is 

 actual need of repair of wasted muscles in consequence of antecedent disease or starva- 

 tion, are not stored up in the body of the adult, but are burnt up in proportion as 

 they are supplied in the food. Every protein- meal therefore raises the production 

 of heat in the body, and this production of heat is in addition to the heat which is 

 produced by any muscular work undertaken at the same time. A large meat diet, 

 apart from its content in fat, is of no special advantage for the performance of muscular 

 work, and is a distinct disadvantage when this work has to be accomplished at a high 

 external temperature. On the other hand, a diet in which there is a large proportion 

 of meat is of value to men in sedentary occupations in a cold or temperate climate, 

 since it enables them to maintain their body temperature without the necessity of 

 bodily exercise. The idea that the heavy worker requires a large supply of butcher's 

 meat is of doubtful foundation, though there is no doubt that, in occupations involving 

 exposure to cold and wet, a large supply of meat will add to the comfort of the individual 

 by keeping him warm. 



One other fact is of importance in this connection. Meat is not only easily cooked 

 and presented in a palatable form, but its flavour renders other kinds of foods accept- 

 able, at any rate to most inhabitants of the temperate and northern parts of Europe. 

 It is thus habit rather than strict physiological principles which will probably govern 

 the quantity of meat regarded as desirable in the normal diets of such people. 



The significance of Sugar. Sugar is the only food which is chemically purified before 

 forming part of the diet. As a source of energy to the body it is nearly equivalent to 

 an equal weight of starch. Its taste however renders it of value by increasing the 

 palatability of other foods, and on this account a sufficient supply of sugar should be 

 available for those classes whose facilities for cooking are defective. Sugar is readily 

 absorbed from the alimentary canal and is the most useful food for sustaining 

 muscular effort. 



We thus see that a dietary to maintain a man in health and efficiency 

 must fulfil the following requirements : 



(1) It must have a sufficient Calorie value (3300 for the average man). 



(2) It must contain protein, fats and carbohydrates. The quantity of 



