364 THE HUMAN BODY AND ITS FOOD 



but also for their efficiency in their work ; that is, for what 

 they do as compared with what they could do. 



A grown man, weighing about 154 pounds, and doing a moderate 

 amount of muscular work, needs from 60 to 115 grams (3 to 5 ounces) 

 of proteids per day. Part of these may be vegetable proteids. In 

 addition, he needs enough fats and carbohydrates to give him energy to 

 the amount of 3,000 or 3,400 large calories. A large calorie is 1,000 

 ordinary calories (cf. 64). This is about the amount of heat pro- 

 duced by the burning of 1 pound of carbon. We commonly get our 

 energy from cereals, bread, potatoes, sugar, fat, etc. 



There is a great difference in the price of foods, when they are 

 considered as energy-producers. If corn costs l l /2 cents a pound, 1 

 cent's worth of corn will give off 1,200 calories of heat, while 1 cent's 

 worth of codfish will give off only 20 calories, and 1 cent's worth of 

 oysters only 12 calories. Unless a family is careful, it may pay high 

 prices for food, and yet not be as well nourished as a family with a 

 simple and inexpensive, but well selected diet. 



But we must remember that fresh vegetables, which give us almost 

 no proteid and fat, and but little carbohydrate, are very important 

 for the mineral salts they contain, and because they give bulk to our 

 food. We cannot estimate the value of a food in terms of proteids and 

 energy alone. 



Whether food is cheap or expensive, it should be made 

 appetizing and nutritious by proper cooking and serving. 

 Cooking does not add to the nutrients of the food, but it 

 adds greatly to the digestibility. It softens arid loosens 

 the tissues of food, and enables the digestive juices to get 

 at them. Proper cooking kills the parasites, such as 

 bacteria, that cling to food, and the trichinae (small 

 worms) and young tapeworms that are sometimes found 

 in raw meat. Meat is especially likely to be improperly 

 cooked. If it is fried or roasted, it should be seared on 

 the outside by being heated very hot at once; in this way 



