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FOOD
Оглавление55. The Body as a Machine. Wholesome food and fresh air are necessary for a healthy body. Many housewives, through ignorance, supply to their hard-working husbands and their growing sons and daughters food which satisfies the appetite, but which does not give to the body the elements needed for daily work and growth. Some foods, such as lettuce, cucumbers, and watermelons, make proper and satisfactory changes in diet, but are not strength giving. Other foods, like peas and beans, not only satisfy the appetite, but supply to the body abundant nourishment. Many immigrants live cheaply and well with beans and bread as their main diet.
It is of vital importance that the relative value of different foods as heat producers be known definitely; and just as the yard measures length and the pound measures weight the calorie is used to measure the amount of heat which a food is capable of furnishing to the body. Our bodies are human machines, and, like all other machines, require fuel for their maintenance. The fuel supplied to an engine is not all available for pulling the cars; a large portion of the fuel is lost in smoke, and another portion is wasted as ashes. So it is with the fuel that runs the body. The food we eat is not all available for nourishment, much of it being as useless to us as are smoke and ashes to an engine. The best foods are those which do the most for us with the least possible waste.
FIG. 26.—The bomb calorimeter from which the fuel value of food can be estimated.
56. Fuel Value. By fuel value is meant the capacity foods have for yielding heat to the body. The fuel value of the foods we eat daily is so important a factor in life that physicians, dietitians, nurses, and those having the care of institutional cooking acquaint themselves with the relative fuel values of practically all of the important food substances. The life or death of a patient may be determined by the patient's diet, and the working and earning capacity of a father depends largely upon his prosaic three meals. An ounce of fat, whether it is the fat of meat or the fat of olive oil or the fat of any other food, produces in the body two and a quarter times as much heat as an ounce of starch. Of the vegetables, beans provide the greatest nourishment at the least cost, and to a large extent may be substituted for meat. It is not uncommon to find an outdoor laborer consuming one pound of beans per day, and taking meat only on "high days and holidays."
The fuel value of a food is determined by means of the bomb calorimeter (Fig. 26). The food substance is put into a chamber A and ignited, and the heat of the burning substance raises the temperature of the water in the surrounding vessel. If 1000 grams of water are in the vessel, and the temperature of the water is raised 2° C., the number of calories produced by the substance would be 2000, and the fuel value would be 2000 calories.[A] From this the fuel value of one quart or one pound of the substance can be determined, and the food substance will be said to furnish the body with that number of heat units, providing all of the pound of food were properly digested.
[Footnote A: As applied to food, the calorie is greater than that used in the ordinary laboratory work, being the amount of heat necessary to raise the temperature of 1000 grams of water 1° C., rather than 1 gram 1° C.]
TABLE SHOWING THE NUMBER OF CALORIES FURNISHED BY
ONE POUND OF VARIOUS FOODS
| FOOD | CALORIES | FOOD | CALORIES |
| Leg of lean mutton | 790 | Carrots | 210 |
| Rib of beef | 1150 | Lettuce | 90 |
| Shad | 380 | Onion | 225 |
| Chicken | 505 | Cucumber | 80 |
| Apples | 290 | Almonds | 3030 |
| Bananas | 460 | Walnuts | 3306 |
| Prunes | 370 | Peanuts | 2560 |
| Watermelons | 140 | Oatmeal | 4673 |
| Lima beans | 570 | Rolled wheat | 4175 |
| Beets | 215 | Macaroni | 1665 |
57. Varied Diet. The human body is a much more varied and complex machine than any ever devised by man; personal peculiarities, as well as fuel values, influence very largely the diet of an individual. Strawberries are excluded from some diets because of a rash which is produced on the skin, pork is excluded from other diets for a like reason; cauliflower is absolutely indigestible to some and is readily digested by others. From practically every diet some foods must be excluded, no matter what the fuel value of the substance may be.
Then, too, there are more uses for food than the production of heat. Teeth and bones and nails need a constant supply of mineral matter, and mineral matter is frequently found in greatest abundance in foods of low fuel value, such as lettuce, watercress, etc., though practically all foods yield at least a small mineral constituent. When fuel values alone are considered, fruits have a low value, but because of the flavor they impart to other foods, and because of the healthful influence they exercise in digestion, they cannot be excluded from the diet.
Care should be constantly exercised to provide substantial foods of high fuel value. But the nutritive foods should be wisely supplemented by such foods as fruits, whose real value is one of indirect rather then direct service.
58. Our Bodies. Somewhat as a house is composed of a group of bricks, or a sand heap of grains of sand, the human body is composed of small divisions called cells. Ordinarily we cannot see these cells because of their minuteness, but if we examine a piece of skin, or a hair of the head, or a tiny sliver of bone under the microscope, we see that each of these is composed of a group of different cells. A merchant, watchful about the fineness of the wool which he is purchasing, counts with his lens the number of threads to the inch; a physician, when he wishes, can, with the aid of the microscope, examine the cells in a muscle, or in a piece of fat, or in a nerve fiber. Not only is the human body composed of cells, but so also are the bodies of all animals from the tiny gnat which annoys us, and the fly which buzzes around us, to the mammoth creatures of the tropics. These cells do the work of the body, the bone cells build up the skeleton, the nail cells form the finger and toe nails, the lung cells take care of breathing, the muscle cells control motion, and the brain cells are responsible for thought.
59. Why we eat so Much. The cells of the body are constantly, day by day, minute by minute, breaking down and needing repair, are constantly requiring replacement by new cells, and, in the case of the child, are continually increasing in number. The repair of an ordinary machine, an engine, for example, is made at the expense of money, but the repair and replacement of our human cell machinery are accomplished at the expense of food. More than one third of all the food we eat goes to maintain the body cells, and to keep them in good order. It is for this reason that we consume a large quantity of food. If all the food we eat were utilized for energy, the housewife could cook less, and the housefather could save money on grocer's and butcher's bills. If you put a ton of coal in an engine, its available energy is used to run the engine, but if the engine were like the human body, one third of the ton would be used up by the engine in keeping walls, shafts, wheels, belts, etc., in order, and only two thirds would go towards running the engine. When an engine is not working, fuel is not consumed, but the body requires food for mere existence, regardless of whether it does active work or not. When we work, the cells break down more quickly, and the repair is greater than when we are at rest, and hence there is need of a larger amount of food; but whether we work or not, food is necessary.
60. The Different Foods. The body is very exacting in its demands, requiring certain definite foods for the formation and maintenance of its cells, and other foods, equally definite, but of different character, for heat; our diet therefore must contain foods of high fuel value, and likewise foods of cell-forming power.
Although the foods which we eat are of widely different character, such as fruits, vegetables, cereals, oils, meats, eggs, milk, cheese, etc., they can be put into three great classes: the carbohydrates, the fats, and the proteids.
61. The Carbohydrates. Corn, wheat, rye, in fact all cereals and grains, potatoes, and most vegetables are rich in carbohydrates; as are also sugar, molasses, honey, and maple sirup. The foods of the first group are valuable because of the starch they contain; for example, corn starch, wheat starch, potato starch. The substances of the second group are valuable because of the sugar they contain; sugar contains the maximum amount of carbohydrate. In the sirups there is a considerable quantity of sugar, while in some fruits it is present in more or less dilute form. Sweet peaches, apples, grapes, contain a moderate amount of sugar; watermelons, pears, etc., contain less. Most of our carbohydrates are of plant origin, being found in vegetables, fruits, cereals, and sirups.
Carbohydrates, whether of the starch group or the sugar group, are composed chiefly of three elements: carbon, hydrogen, and oxygen; they are therefore combustible, and are great energy producers. On the other hand, they are worthless for cell growth and repair, and if we limited our diet to carbohydrates, we should be like a man who had fuel but no engine capable of using it.
62. The Fats. The best-known fats are butter, lard, olive oil, and the fats of meats, cheese, and chocolate. When we test fats for fuel values by means of a calorimeter (Fig. 26), we find that they yield twice as much heat as the carbohydrates, but that they burn out more quickly. Dwellers in cold climates must constantly eat large quantities of fatty foods if they are to keep their bodies warm and survive the extreme cold. Cod liver oil is an excellent food medicine, and if taken in winter serves to warm the body and to protect it against the rigors of cold weather. The average person avoids fatty foods in summer, knowing from experience that rich foods make him warm and uncomfortable. The harder we work and the colder the weather, the more food of that kind do we require; it is said that a lumberman doing heavy out-of-door work in cold climates needs three times as much food as a city clerk. Most of our fats, like lard and butter, are of animal origin; some of them, however, like olive oil, peanut butter, and coconut oil, are of plant origin.
FIG. 27.—a is the amount of fat necessary to make one calorie; b is the amount of sugar or proteid necessary to make one calorie.
63. The Proteids. The proteids are the building foods, furnishing muscle, bone, skin cells, etc., and supplying blood and other bodily fluids. The best-known proteids are white of egg, curd of milk, and lean of fish and meat; peas and beans have an abundant supply of this substance, and nuts are rich in it. Most of our proteids are of animal origin, but some protein material is also found in the vegetable world. This class of foods contains carbon, oxygen, and hydrogen, and in addition, two substances not found in carbohydrates or fats—namely, sulphur and nitrogen. Proteids always contain nitrogen, and hence they are frequently spoken of as nitrogenous foods. Since the proteids contain all the elements found in the two other classes of foods, they are able to contribute, if necessary, to the store of bodily energy; but their main function is upbuilding, and the diet should be chosen so that the proteids do not have a double task.
For an average man four ounces of dry proteid matter daily will suffice to keep the body cells in normal condition.
It has been estimated that 300,000,000 blood cells alone need daily repair or renewal. When we consider that the blood is but one part of the body, and that all organs and fluids have corresponding requirements, we realize how vast is the work to be done by the food which we eat.
FIG. 28.—Table of food values.
64. Mistakes in Buying. The body demands a daily ration of the three classes of food stuffs, but it is for us to determine from what meats, vegetables, fruits, cereals, etc., this supply shall be obtained (Figs. 28 and 29).
FIG. 29.—Diagram showing the difference in the cost of three foods which give about the same amount of nutrition each.
Generally speaking, meats are the most expensive foods we can purchase, and hence should be bought seldom and in small quantities. Their place can be taken by beans, peas, potatoes, etc., and at less than a quarter of the cost. The average American family eats meat three times a day, while the average family of the more conservative and older countries rarely eats meat more than once a day. The following tables indicate the financial loss arising from an unwise selection of foods:—
FOOD CONSUMED—ONE WEEK
| FAMILY No. 1 | FAMILY No. 2 | ||
| 20 loaves of bread | $ 1.00 | 15 lb. flour, bread home-made (skim milk used) | $ 0.45 |
| 10 to 12 lb. loin steak or meat similar cost | 2.00 | Yeast, shortening, and skim milk | 0.10 |
| 20 to 25 lb. rib roast or similar meat | 4.40 | 10 lb. steak (round, Hamburger and some loin) | 1.50 |
| 4 lb. high-priced cereal breakfast food, 20¢ | 0.80 | 10 lb. other meats, boiling pieces, rump roast, etc. | 1.00 |
| Cake and pastry purchased | 3.00 | 5 lb. cheese, 16¢ | 0.80 |
| 8 lb. butter, 30¢ | 2.40 | 5 lb. oatmeal (bulk) | 0.15 |
| Tea, coffee, spices, etc. | 0.75 | 5 lb. beans | 0.25 |
| Mushrooms | 0.75 | Home-made cake and pastry | 1.00 |
| Celery | 1.00 | 6 lb. butter, 30¢ | 1.80 |
| Oranges | 2.00 | 3 lb. home-made shortening | 0.25 |
| Potatoes | 0.25 | Tea, coffee, and spices | 0.40 |
| Miscellaneous canned goods | 2.00 | Apples | 0.50 |
| Milk | 0.50 | Prunes | 0.25 |
| Miscellaneous foods | 2.00 | Potatoes | 0.25 |
| 3 doz. eggs | 0.60 | Milk | 1.00 |
| Miscellaneous foods | 1.00 | ||
| 3 doz. eggs | 0.60 | ||
| $23.45 | $11.30 |
"The tables show that one family spends over twice as much in the purchase of foods as the other family, and yet the one whose food costs the less actually secures the larger amount of nutritive material and is better fed than the family where more money is expended."—From Human Foods, Snyder.
The Source of the Different Foods. All of our food comes from either the plant world or the animal world. Broadly speaking, plants furnish the carbohydrates, that is, starch and sugar; animals furnish the fats and proteids. But although vegetable foods yield carbohydrates mainly, some of them, like beans and peas, contain large quantities of protein and can be substituted for meat without disadvantage to the body. Other plant products, such as nuts, have fat as their most abundant food constituent. The peanut, for example, contains 43% of fat, 30% of proteids, and only 17% of carbohydrates; the Brazil nut has 65% of fat, 17% of proteids, and only 9% of carbohydrates. Nuts make a good meat substitute, and since they contain a fair amount of carbohydrates besides the fats and proteins, they supply all of the essential food constituents and form a well-balanced food.
