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ОглавлениеVALUE OF FOOD TO THE BODY
“Food is that which when taken into the body tends either to build tissue or to yield energy.”
The chief offices of food are to build the material of the body, to repair the waste which is continually going on and to yield heat to keep the body warm.
Foods may be divided into tissue-building foods and fuel foods.
The tissue-building foods are such foods as milk, eggs, cheese, wheat, meat and the legumes. The fuel foods are sugars and starches and fats and oils.
In order to keep the body in a good condition a combination of the tissue-building foods and the fuel foods is necessary, with a supply of water to dissolve them. About 125 grams of tissue-building foods and 550 grams of the fuel foods is the amount required daily. A mixed diet, therefore, is the ideal diet for the healthy adult.
The changing of the tissues and the assimilation of food are very rapid in childhood and youth, so that the system demands at that time an abundant supply of such foods as meat, milk and eggs. When middle age is reached, the amount of such food should be decreased. Otherwise the tax on the organs which take care of the wastes will be so great that disease will follow.
Thus it is clear that people of different ages require different combinations and amounts of food. The kinds of food required to nourish the healthy body vary also with the sex, occupation and climate, as well as with the age and peculiarities of the individual. In order to judge of the relative value of food to the body it is necessary to find out what percentage of each nutritive constituent the food contains, how much energy it is capable of yielding, how much of the food eaten is digested, how much is absorbed, and whether the nutritive constituents are obtained at a reasonable cost.
Farmers’ Bulletin No. 23, published by the United States Department of Agriculture, will be found interesting to those caring to study foods from the above standpoints.
Mr. W. O. Atwater, Ph. D., writes in Farmers Bulletin No. 142, on “Food and Food Economy,” the following table:—
Nutritive Ingredients (or Nutrients) of Food
| Food as purchased contains: | Edible portion e.g., flesh of meat yolk and white of eggs wheat, flour, etc. Refuse. e.g., bones, entrails, shell, bran, cellulose, etc. | Water Nutrients— | Protein Fats Carbohydrates Mineral matters |
Uses of Nutrients in the Body
| Protein | Forms tissue | — | All serve as fuel to yield energy in the forms of heat and muscular power. | |
| e.g., white (albumen) of eggs | ||||
| curd (casein) of milk | ||||
| lean meat | ||||
| gluten of wheat, etc. | ||||
| Fats | Are stored as fat | |||
| e.g., fat of meat, butter, olive oil | ||||
| oils of corn, wheat, etc. | ||||
| Carbohydrates | Transformed into fat | |||
| e.g., sugar, starch, etc. | ||||
| Mineral Matters (ash) | Share in forming bone, assist in digestion, etc. | |||
| e.g., phosphates of lime | ||||
| potash, soda, etc. |
Thus foods have different functions. The proteid or nitrogenous foods build up and repair the tissues; mineral matter and water are also necessary for this purpose. The tissues of the body cannot be kept in a healthy state unless these constituents of food are taken into the system regularly; only the proteid foods can repair the waste of the living tissue. The proteid foods, together with the fats and carbohydrates, may supply both power and heat for the body, but the special functions of the carbohydrates and fats are to keep the body warm and to supply energy.
The amount of proteid food required for a healthy adult is very difficult to determine. It is safe to state that too much proteid brings about undue strain upon the digestive apparatus, and that too little proteid reduces the working equipment of the body. The amount of fats and carbohydrates needed depend largely upon occupation and climate. The proteid foods are many, and contain the same chemical elements as the bodies which they are destined to feed; also they seem to be more completely taken care of in the body than the carbohydrate foods. Milk, cheese, eggs, meat, and fish are proteid foods. Of these milk is regarded as a typical food, as it contains all the nutritive constituents required by the body,—proteid, carbohydrates, fats, mineral matter, and water,—but it does not contain these constituents in the correct proportion. It is too rich in proteid and fat and too poor in carbohydrate to be a perfect food. It is a perfect food for the infant, because an excess of proteid and of fat is needed for the growth of the child. For the healthy man about eight pints daily would be required for complete nutrition. This, it is apparent, would be a very bulky food, and the system would be burdened with too large a proportion of water. Milk, on the other hand, is the cheapest source of proteid. It is claimed that one quart of good milk is equivalent in proteid to a pound of beefsteak, and that when combined with the correct proportion of carbohydrate food it possesses great nutritive and economic value. All of the proteid foods are deficient in starch, so must be combined with carbohydrates to properly nourish the body.
According to Mr. Atwater the proteid foods are more completely digested than the carbohydrates. This is probably because there is found in all carbohydrate foods a large proportion of cellulose or indigestible material enveloping the starch and sugar. The nutritive value of the carbohydrate foods is large if the starch and sugar, of which they are composed, can be separated from the cellulose. The normal diet is one which contains proteid foods, carbohydrate foods, fatty foods, with the correct proportion of mineral matter and sufficient water to moisten them.
The proper diet depends largely upon the occupation. People of sedentary habits and brain workers need more digestible food than the day laborer—therefore, the necessity of mixed diets; but diets should be varied as well as mixed, and the true housekeeper in planning meals thinks what was served at the preceding meal.
The cheapest diet is that which yields the largest amount of nutriment for the least expenditure of money. The most economical diet is that which is cheapest and at the same time best adapted to the needs of the user. The most expensive diet is not necessarily the most nutritious.
Every good housekeeper should know approximately the composition of the various foodstuffs, and so be able to make proper combinations of foods and substitutions when necessary. Hunger and thirst are provided by nature as guides in the choice of food, and if the bodily conditions are normal, these, as a rule, are safe guides to follow.
The nutritive value of many foods depends upon how they are cooked. Many raw foods are indigestible, but these same foods cooked are nutritious. The importance of proper cooking cannot be overestimated. Cooking changes the food so that the digestive juices can take care of it; cooking improves the flavor and the appearance, thus making the food more appetizing; and cooking kills disease germs, parasites, and other dangerous organisms.
Proper cooking and dainty serving make even cheap foods more palatable. This stimulates the digestive juices; hence food should be made appetizing in order to obtain the greatest nutritive value from it.
