630 METABOLISM 



case of growing children at least, and even in adults it is undoubtedly 

 advisable that other proteins should supplement them. 



To insure safety, therefore, it is almost imperative that the diet should 

 contain proteins of various sources. If for economic reasons the main 

 source must be proteins of vegetable origin, then some animal protein, such 

 as is contained in milk or meat or eggs, should be added to at least one of 

 the daily meals. When peas and beans are mainly depended on for the 

 protein supply, they should be taken either with milk or one of its prep- 

 arations, or with a thick gravy or sauce made from meat and containing 

 the finely minced meat. This must not be strained off, for if it is, the 

 sauce will contain only the meat extractives but not any of the protein, 

 which is coagulated by the boiling water. Meat extract, in other words, 

 contains no proteins; it is not a food but merely a condiment of no greater 

 dietetic value than tea or coffee. 



ACCESSORY FOOD FACTORS 



The practical point to be remembered is that three accessory fac- 

 tors or vitamines are known. There is little danger of the diet being 

 inadequate with regard to food factors if it contains some fruits or 

 green vegetables or unheated fresh milk. Certain of the food factors 

 are destroyed by prolonged cooking. It is during times of food scarcity 

 that the restricted diet may require to be scrutinized to see that it con- 

 tains the essential vitamines. The reader is referred to page 618, where 

 this subject is more fully dealt with. 



DIGESTIBILITY AND PALATABILITY 



We have seen that practical dietetics depends on several factors, the 

 exact relative importance of which can not perhaps be gauged in every 

 case, but preparation of the food so as to make it appetizing must un- 

 doubtedly rank high. The importance of good cooking will now be ap- 

 parent. It is the act of making food appetizing and therefore digestible. 

 It is really the first stage in digestion, the stage that we can control, and one 

 therefore to which much attention must be given, especially when it becomes 

 necessary to make attractive, articles of diet that are ordinarily considered 

 common and cheap. Most people can cook a lamb chop so as to make it 

 reasonably appetizing, but few can take the cheaper cuts of meat and con- 

 vert them into cooked dishes that are as popular and attractive. And there 

 are still fewer who can take the left-overs and trimmings and convert them 

 in the same way. This is the real art of cooking, and too much encourage- 

 ment can not be given to the effort which our cooking experts are making 



