Human Nutrition. 759 



This is one of the functions of mineral matter. Fruits and vegetables, 

 the outer layer of wheat and oats, contain substances which act in 

 this way. The diet should also be somewhat bulky, for the mechanical 

 irritation caused by a not too bulky diet gives rise to intestinal move- 

 ment and aids in throwing off the intestinal waste products. Water 

 is another important factor in this body process. Constipation may 

 be the result of too little water in the diet. One argiunent in favor of 

 whole wheat bread in the diet is because it is more bulky than white 

 bread and because it contains substances which stimulate the activity 

 of the intestine. 



The Family Dietary, 



In planning the family dietary, our first object is to include in a form 

 useful to the body, all the elements w'hich compose it. We must then 

 decide which foods are the most valuable sources of the various food- 

 stuffs, whether milk or eggs or meat is the best source of protein, whether 

 potatoes or bread should furnish the bulk of the starch. The next step 

 is to learn how to determine the amount of food needed each day, and 

 what relative proportion should be protein, carbohydrate and fat. It 

 has become the fashion to say "everyone eats too much." Let us dis- 

 cover the truth, and learn whether it is over eating or wrong eating 

 which is the cause of our ills. 



How food values are measured. — The amount of food which shall be 

 eaten each day is measured in much the same way as the amount of fuel 

 which is required to run an engine. Both body and engine are looked 

 upon as machines doing work and thus spending energy which must 

 be obtained from some outside source, fuel in one case and food in the 

 other. The energy which the body spends in doing its work is a measure 

 of the amount of food required. 



The value of a fuel is determined by the amount of heat it is capable 

 of giving off. A weighed portioh, i gram ( 1-27 ounce), of a fuel such as 

 coal or wood is burned and the heat it produces is used to raise the 

 temperature of a weighed amount, 1 kilogram (2.2 pounds), of water. 

 The rise in temperature in the water is accurately measured with a 

 centigrade thermometer, and each degree rise in temperature produced 

 in the water by burning the fuel is called a heat unit. The name calorie 

 has been given to the heat units found in this way, and the value of 

 a fuel is determined by the number of heat units or calories it can pro- 

 duce For example, if the burning of i gram ( 1-27 ounce) of wood causes 

 a rise of 3 degrees C. in one kilogram (2.2 pounds) of water, it is said to 

 have a fuel value of 3 calories per gram ; and since there are 453 grams 



