Public School Domestic Science

The Relation of Food to the Body.

In order to understand the relation of food to the sustenance and repairing of the body, it will be necessary to learn, first, of what the body is composed, and the corresponding elements contained in the food required to build and keep the body in a healthy condition. The following table gives the approximate analysis of a man weighing 148 pounds:-

Oxygen 92.1 pounds.

Hydrogen 14.6 "

Carbon 31.6 "

Nitrogen 4.6 "

Phosphorus 1.4 "

Calcium 2.8 "

Sulphur 0.24 "

Chlorine 0.12 "

Sodium 0.12 "

Iron 0.02 "

Potassium 0.34 "

Magnesium 0.04 "

Silica ? "

Fluorine 0.02 "

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Total 148.00 pounds.

As food contains all these elements, and as there is constant wearing and repair going on in the body, it will be readily seen how necessary some knowledge of the relation of food to the body is, in order to preserve health.

Hydrogen and oxygen combined form water, hence we find from the above calculation that about three-fifths of the body is composed of water. Carbon is a solid: diamonds are nearly pure carbon; "lead" of lead pencils, anthracite coal and coke are impure forms of carbon. Carbon combined with other elements in the body makes about one-fifth of the whole weight. Carbon with oxygen will burn. In this way the carbon taken into the body as food, when combined with the oxygen of the inhaled air, yields heat to keep the body warm, and force-muscular strength-for work. The carbonic acid (or carbon dioxide) is given out through the lungs and skin. In the further study of carbonaceous foods, their relation to the body as fuel will be more clearly understood, as carbon is the most important fuel element. Phosphorus is a solid. According to the table, about one pound six ounces would be found in a body weighing 148 pounds. United with oxygen, phosphorus forms what is known as phosphoric acid; this, with lime, makes phosphate of lime, in which form it is found in the bones and teeth; it is found also in the brain and nerves, flesh and blood. Hydrogen is a gas, and like carbon unites with the oxygen of the inhaled air in the body, thus serving as fuel. The water produced is given off in the respiration through the lungs and as perspiration through the skin.[3] Calcium is a metal. The table given allows three pounds of calcium; united with oxygen, calcium forms lime. This with phosphoric acid makes phosphate of lime, the basis of the bones and teeth, in which nearly all the calcium of the body is found.

The elements which bear no direct relation to the force production of the body, but which enter into tissue formation, are chlorine, sulphur, iron, sodium, potassium, phosphorus, calcium and magnesium. Bone tissue contains about 50 per cent. of lime phosphate, hence the need of this substance in the food of a growing infant, in order that the bones may become firm and strong. Lack of iron salts in the food impoverishes the coloring matter of the red blood corpuscles on which they depend for their power of carrying oxygen to the tissues; an?mia and other disorders of deficient oxidation result. The lack of sufficient potash salts is a factor in producing scurvy, a condition aggravated by the use of common salt. A diet of salt meat and starches may cause it, with absence of fresh fruit and vegetables. Such illustrations show the need of a well-balanced diet.

In order to understand the value of the various classes of food and their relation to the body as force producers, tissue builders, etc., the following table may prove helpful:-

Nitrogen. C.H.

Combustibles

Calculated as

Carbon

Beef, uncooked 3.00 11.00

Roast beef 3.53 17.76

Calf's liver 3.09 15.68

Foie-gras 2.12 65.58

Sheep's kidneys 2.66 12.13

Skate 3.83 12.25

Cod, salted 5.02 16.00

Herring, salted 3.11 23.00

Herring, fresh 1.83 21.00

Whiting 2.41 9.00

Mackerel 3.74 19.26

Sole 1.91 12.25

Salmon 2.09 16.00

Carp 3.49 12.10

Oysters 2.13 7.18

Lobster, uncooked 2.93 10.96

Eggs 1.90 13.50

Milk (cows') 0.66 8.00

Cheese (Brie) 2.93 35.00

Cheese (Gruyere) 5.00 38.00

Cheese (Roquefort) 4.21 44.44

Chocolate 1.52 58.00

Wheat (hard Southern, variable average) 3.00 41.00

Wheat (soft Southern, variable average) 1.81 39.00

Flour, white (Paris) 1.64 38.50

Rye flour 1.75 41.00

Winter barley 1.90 40.00

Maize 1.70 44.00

Buckwheat 2.20 42.50

Rice 1.80 41.00

Oatmeal 1.95 44.00

Bread, white (Paris, 30 per cent. water) 1.08 29.50

Bread, brown (soldiers' rations formerly) 1.07 28.00

Bread, brown (soldiers' rations at present) 1.20 30.00

Bread, from flour of hard wheat 2.20 31.00

Potatoes 0.33 11.00

Beans 4.50 42.00

Lentils, dry 3.87 43.00

Peas, dry 3.66 44.00

Carrots 0.31 5.50

Mushrooms 0.60 4.52

Figs, fresh 0.41 15.50

Figs, dry 0.92 34.00

Coffee (infusion of 100 grams) 1.10 9.00

Tea (infusion of 100 grams) 1.00 10.50

Bacon 1.29 71.14

Butter 0.64 83.00

Olive oil Trace 98.00

Beer, strong 0.05 4.50

Wine 0.15 4.00

"The hydrogen existing in the compound in excess of what is required to form water with the oxygen present is calculated as carbon. It is only necessary to multiply the nitrogen by 6.5 to obtain the amount of dry proteids in 100 grams of the fresh food substance." (Dujardin-Beauretz.) The following simple rules are given by Parks:-"1st. To obtain the amount of nitrogen in proteid of foods, divide the quantity of food by 6.30. 2nd. To obtain the carbon in fat multiply by 0.79. 3rd. To obtain the carbon in carbohydrate food multiply by 0.444. 4. To obtain the carbon in proteid food multiply by 0.535."

Finding that our food and our bodies contain essentially the same elements, we must also bear in mind that the body cannot create anything for itself, neither material nor energy; all must be supplied by the food we eat, which is transformed into repair material for the body. Therefore, the object of a course of study dealing with the science of this question, as it relates to the daily life, should be to learn something of how food builds the body, repairs the waste, yields heat and energy, and to teach the principles of food economy in its relation to health and income. This, with the development of executive ability, is all that can be attempted in a primary course.

FOOTNOTE:

[3] An illustration of vapor rising may be given by breathing upon a mirror.

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Food Classification.

The following are familiar examples of compounds of each of the four principal classes of nutrients:

Protein:

Proteids.

Albuminoids, e.g., albumen of eggs; myosin, the basis of muscle (lean meat); the albuminoids which make up the gluten of wheat, etc.

Gelatinoids, constituents of connective tissue which yield gelatin and allied substances, e.g., collagen of tendon; ossein of bone.

"Nitrogenous extractives" of flesh, i.e., of meats and fish. These include kreatin and allied compounds, and are the chief ingredients of beef tea and most meat extracts. Amids: this term is frequently applied to the nitrogenous non-albuminoid compounds of vegetable foods and feeding stuffs, among which are amido acids, such as aspartic acid and asparagin. Some of them are more or less allied in chemical constitution to the nitrogenous extractives of flesh.

Fats.

Fat of meat: fat of milk; oil of corn, wheat, etc. The ingredients of the "ether extract" of animal and vegetable foods and feeding stuffs, which it is customary to group together roughly as fats, include, with the true fats, various other substances, as lecithians, and chlorophylls.

Carbohydrates, sugars, starches, celluloses, gums, woody fibre, etc.

Mineral matter.

Potassium, sodium, calcium and magnesium chlorids, sulphates and phosphates. (Atwater).

The terms (a) "nitrogenous" and (b) "carbonaceous" are frequently used to designate the two distinct classes of food, viz.: (a) the tissue builders and flesh formers; (b) fuel and force producers.

Each of these classes contains food material derived from both the animal and vegetable kingdom, although the majority of the animal substances belong to the nitrogenous, and the majority of the vegetable substances to the carbonaceous group.

Therefore, for practical purposes, we will confine ourselves to the more general terms used in Atwater's table.

Uses of Food.

First, food is used to form the materials of the body and repair its waste; second, to yield energy in the form of (1) heat to keep the body warm, (2) to provide muscular and other power for the work it has to do. In forming the tissues and fluids of the body the food serves for building and repair. In yielding energy, it serves as fuel for heat and power. The principal tissue formers are the albuminoids; these form the frame-work of the body. They build and repair the nitrogenous materials, as those of muscle, tendon and bone, and supply the albuminoids of blood, milk and other fluids. The chief fuel ingredients of food are the carbohydrates and fats. These are either consumed in the body or are stored as fat to be used as occasion demands.

Water.

By referring to a preceding chapter we find that water composes three-fifths of the entire body. The elasticity of muscles, cartilage, tendons, and even of bones is due in great part to the water which these tissues contain. The amount of water required by a healthy man in twenty-four hours (children in proportion) is on the average between 50 and 60 ounces, beside about 25 ounces taken as an ingredient of solid food, thus making a total of from 75 to 85 ounces. One of the most universal dietetic failings is neglect to take enough water into the system. Dr. Gilman Thompson gives the following uses of water in the body:-

(1) It enters into the chemical composition of the tissues; (2) it forms the chief ingredient of all the fluids of the body and maintains their proper degree of dilution; (3) by moistening various surfaces of the body, such as the mucous and serous membranes, it prevents friction and the uncomfortable symptoms which might result from drying; (4) it furnishes in the blood and lymph a fluid medium by which food may be taken to remote parts of the body and the waste matter removed, thus promoting rapid tissue changes; (5) it serves as a distributer of body heat; (6) it regulates the body temperature by the physical processes of absorption and evaporation.

Salts (Mineral Matter).-Use of Salts in Food.

(1) To regulate the specific gravity of the blood and other fluids of the body; (2) to preserve the tissues from disorganization and putrefaction; (3) to enter into the composition of the teeth and bones. These are only a few of the uses of salts in the body, but are sufficient for our purpose. Fruits and nuts contain the least quantity of salts, meat ranks next, then vegetables and pulses, cereals contain most of all (Chambers). Sodium chloride (common salt) is the most important and valuable salt. It must not however be used in excess. Potassium salts rank next in importance.[4] Calcium, phosphorus, sulphur and iron are included in this class.

The quantity of salts or mineral matter contained in some important articles of vegetable and animal food is shown in this table (Church):

Mineral Matter in 1,000 lbs. of 14 Vegetable Products.

Lbs.

Apples 4

Rice 5

Wheaten flour 7

Turnips 8

Potatoes 10

Barley 11

Cabbage 12

Bread 12

Watercress 13

Maize 20

Oatmeal 21

Peas 30

Cocoa nibs 36

Wheaten bran 60

Mineral Matter in 1,000 lbs. of 8 Animal Products.

Lbs.

Fat Pork 5

Cow's milk 7

Eggs (without shells) 13

Lean of mutton 17

Flesh of common fowl 16

Bacon 44

Gloucester cheese 49

Salted herrings 158

"In most seeds and fruits there is much phosphate in the mineral matter, and in most green vegetables much potash. One important kind of mineral matter alone is deficient in vegetable food, and that is common salt."

FOOTNOTE:

[4] See Vegetables, Chap. VII.

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Nutrition.

It is not within the scope of this book to deal with the science of nutrition; but a few general principles may be given which concern the effect upon the system of the different classes of food. Animal food requires a considerable quantity of oxygen for its complete combustion. Meat in general has a more stimulating effect upon the system and is more strengthening than vegetable food. There is, however, a tendency to eat too much meat, and when its effects are not counter-balanced by free outdoor exercise, it causes biliousness and sometimes gout and other troubles. Albuminous foods can be eaten longer alone without exciting loathing than can fats, sugars or starches. A carbonaceous diet taxes the excretory organs less than animal food. Meat is not necessary to life. Nitrogenous food man must have, but it need not be in the form of meat. The estimate commonly given is, that meat should occupy one-fourth and vegetable food three-fourths of a mixed diet, but in many cases the meat eaten is much in excess of this allowance. The proper association of different foods always keeps healthy people in better condition; there are times, however, when it may be necessary to abstain from certain articles of diet. It may be well to bear in mind, that the protein compounds can do the work of the carbohydrates and fats in being consumed for fuel, but the carbohydrates and fats cannot do the work of protein in building and repairing the tissues of the body. As already stated, a mixed diet is the only rational one for man. An exclusively vegetable diet, while it may maintain a condition of health for a time, eventually results in a loss of strength and power to resist disease. Therefore it is necessary to understand the approximate value of each class of food in arranging the daily dietary.

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