Nutrition and diet; a textbook for secondary schools

Front matter

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Preface

Domestic Science as taught in the schools of this country has three distinct phases : practical work in foods, commonly called cooking, and taught in the school kitchen ; experimental work in foods, taught in the chemical laboratory ; and the acquisition of knowledge concerning foods, nutrition, and diet, and its correlation with the knowledge gained in the kitchen and laboratory.

The first phase of the work is usually formulated in some type of cook book, the second in a laboratory manual, and the third phase, because of the lack of suitable textbooks for secondary schools, has been presented by the lecture method.

While several good college texts are published, there has been no book suited to the needs of high school pupils, and the result has been that the teacher has been obliged to dictate her college notes, adapted in some form, to her pupils. These notes, in subject matter and language, have been hard for the immature mind to grasp, and so much time had to be given to dictation that no time was left for recitation or for practical work in carrying out the plans formulated by the teacher.

The lecture method has no place in the secondary school. Time spent in copying notes in class, and then recopying in ink into a notebook is worse than wasted, and it leaves no time for supplementary reading matter to which the teacher could refer the pupil.

4 PREFACE

Such has been the experience of the author of this book, and as a result of this experience, the subject matter prepared, formerly dictated to classes, copied into notebooks, and learned for recitation by the pupils, has been put into form and appears in this volume.

The subject matter is intended for classes that have had at least one half-year's work in practical cooking and some knowledge of foods. If cooking is taught as a high school subject, this book may be used to complement the work in cooking. In many schools a certain num'ber of periods a week are allowed for study and recitation, and a certain number for practical work, in kitchen or laboratory.

This little volume, " Nutrition and Diet," is designed to supplement the practical and experimental work and unify the whole so that the student will know proper foods and the relation of food to health, strength, and efficiency.

Many tables used in this volume are taken from United States Government bulletins ; in fact, unless credit is otherwise given, all the percentage composition tables are taken from the Government publications, as are also the tables called the Atwater Tables. All tables and menus in Chapter VI, Part One, were worked out by the author's classes in 191 2, and the meals were served exactly as they are

outlined.

EMMA CONLEY.

OsHKosH, Wisconsin.

Chapter I Composition Of The Human Body And Of

FOODS

Introductory. — The medicine of the future is prevention. The time is coming when it will be considered as gross ignorance or carelessness to be sick as it now is to be unable to read and write. Almost every magazine and newspaper maintains a department, conducted, not as of old, to prescribe popular remedies for common ills, but to teach people how to keep well.

To-day we have little sympathy for the dyspeptic after we see him consume foods that are almost indigestible to the average person. We know that every case of typhoid fever is due to criminal carelessness on the part of some one. We know that if the sufferer had had plenty of nourishing food and an abundance of fresh air, nearly every case of tuberculosis could be prevented. We know that many diseases are due to lack of attention to the proper ehmination of the wastes of the system, and that rheumatism is tissue poisoning. In fact, some one has well said, that if we looked after breathing, digestion, and elimination of waste, we should never be sick.

It is necessary to have some knowledge to look after the different functions of the body. We must know the composition of the body and what substances it is made of, how the body secures these substances, in what form they are best suppHed, where they are found, how they act when taken into the body, how the body rids itself of their oxidation products, and in what foods substances which the body lacks are to be found.

To acquire this knowledge we must take short journeys into the fields of biology, physiology, chemistry; but the facts are easily learned and the reward is health.

Domestic science is no longer mere cooking. It is a mastery of the principles of cooking and their application to foods. It is vastly more than that. It is a study of foods, — their composition, structure, nutritive value, and place in the diet, — so that when a food is to be served, we know what it furnishes to the body, what effect heat has upon it, what conditions affect its digestibihty, and in what proportions it is best to serve it. In short, domestic science is the study of foods so as to know how to nourish the body.

To find how the body is best served, we must know its composition, the composition of the substances with which we expect to nourish it, and how these substances act in the body. If we do not know these things, all knowledge of cooking is of little avail.

Food Defined and Classified. — Food is any substance which, when taken into the body, supplies it with energy or builds tissue. Foods are oxidized or burned in the body, just as wood or coal is burned outside the body, and that oxidation produces energy. They produce just as much energy when burned in the body as fat or sugar would produce if burned in a stove or in the chemical laboratory. The energy produced in the body by the oxidation of foods is used to maintain the normal temperature of the body ;

and to carry on the vital processes, — as digestion, circulation, respiration; and for work and activity.

The body is made up of an aggregation of cells, and collections of these cells, having special functions, make up the tissues and organs of the body. The cells and tissues of the body are being constantly worn out, and new ones must be built up from, or out of, the food taken into the body. The burning of food and cells in the body is called oxidation, and constitutes the vital process called life.

Not all foods can build tissue. The cells and tissues of the body contain nitrogen, and hence the only foods that will build tissues are those which contain nitrogen. A food which contains carbon will yield energy when oxidized.

Foods are grouped into five classes : proteins, fats, carbohydrates, mineral matter, and water. Proteins contain carbon, hydrogen, oxygen, nitrogen, and sulphur. Fats and carbohydrates contain carbon, hydrogen, and oxygen. Proteins, mineral matter, and water build tissue ; fats, carbohydrates, and proteins yield energy.

Foods are also classified as animal and vegetable foods. Examples of animal foods are meat, fish, eggs, cheese, milk, fat. Examples of vegetable foods are potatoes, carrots, rice, wheat, peas, apples.

Structure of Foods. Animal and Vegetable Cells. — All foods, whether animal or vegetable, are similar in structure in that they are mxade up of innumerable cells held together by some intercellular substance. An animal cell consists of a tiny mass of protoplasm having a center called a nucleus and sometimes surrounded by a cell wall. The nucleus may be called the Hfe center of the cell, because it controls growth and reproduction; the protoplasm contains the nourishment. The protoplasm and the lO

Cells from Human Body (Magnified).

a, a colored cell from the eye; b, a white blood cell; c, a connective tissue cell; d, a cell from lining of the mouth; e, liver cells; /, a muscle cell from the intestine. (From Overton's Applied Physiology.)

nucleus are composed of protein, mineral matter, and water, and they get these substances for their growth and

reproduction from the blood. The digested food is absorbed and becomes part of the blood, and thus reaches the cells, where it becomes new cells, or is oxidized and produces energy.

Animal cells are held together by an intercellular substance called connective tissue. Sometimes fat is found between the cells. Fat is stored in cell walls of connective tissue, and forms adipose or fatty tissue. All animal tissue, whether bone, nerve, or muscle, is made up of cells, composed of substances which are formed from the food which is eaten and which is carried to the cells in the blood.

Vegetable cells consist of a nucleus or life center, and a network of protoplasm ; inclosed in this network are starch grains, mineral matter, and water. The whole is surrounded by a wall of cellulose — a substance

similar in composition to starch, but unlike it in structure. Cellulose also holds vegetable cells together.

Fat Tissues (Magnified).

Connective tissue cells from pockets in which the liquid fat is stored.

II

The protoplasm in vegetable cells consists of protein, and is similar in structure to that in animal cells. In some foods it is so slight that there is scarcely a trace of it, in others it makes up from one seventh to one half of the solid nutrients. Starch or sugar, and some mineral matter, are found in all vegetable cells. Starch is the form in which the nourishment is stored in the plant for the seed. When the seed germinates, the starch is turned to sugar, and in this form it circulates in the plant. Starch may be called stored nourishment and sugar circulating nourishment. Vegetable foods are best for human consumption before they begin to germinate. Fat is found in some vegetable cells.

The cellulose which surrounds the cell cannot be digested in the human stomach and must be softened by cooking to free the inclosed starch and protein.

Uses of Foods. — Every cell in the body is constructed out of the food taken into the body. Food is made over in the body into flesh, bone, nerve, and blood. Food is also oxidized in the body and furnishes energy needed for work and activity and to carry on the vital processes, and to maintain the right bodily temperature. The complete food for any animal must contain all the elements of which its tissues and all the fluids of its body are composed, and it must contain them in the right proportion. If they are

A Thin Slice of Potato (Magnified).

;, albuminous pockets; h, starch grains in the pockets. (From Overton's Applied Physiology.)

not supplied in the proper proportion, the body will be weakened because of the deficiency. A familiar example of this impairment of tissues is seen in the disease called rickets. In this disease not enough mineral matter is supplied to children, and the bones are soft and cannot bear the weight of the body without bending out of shape. When lime is supplied in the right proportion, the bones become hard.

The words Element and Compound are terms used in chemistry to distinguish different forms of matter. An element is a substance which has not been separated into other substances. A compound is a substance composed of two or more elements united in definite proportion : Example. Iron is a substance which has not been separated into other substances. Water is a combination of two substances, hydrogen and oxygen, united in the definite proportion of two parts of hydrogen to one part of oxygen (H2O). Iron is an element ; water is a compound.

Elements found in the Body. — There are eighty or more elements known to the chemical world, and thirteen of these are found to make up the human body. They are oxygen (62I %), carbon (21^ %), hydrogen (10 %), nitrogen (3 %)• Calcium, phosphorus, potassium, chlorine, sodium, magnesium, iron, sulphur, and fluorine make up the remaining 3 per cent. There are, also, traces of iodine, silicon, and several other elements. All these elements are derived from the food taken into the body, and each one has its use and is necessary for the maintenance of a healthy body.

Occurrence in the Body. — Though the body is made up of these thirteen elements, they do not occur as elements, but as compounds, and as compounds they form the various cells and tissues of the body. Albumin, composed of carbon, hydrogen, oxygen, nitrogen, sulphur, and sometimes phosphorus, is found in all the cells of the body. It enters into the structure of the brain, nerves, muscles, and blood. Fat, composed of carbon, hydrogen, and oxygen, is found all over the body, covering the muscles, surrounding internal organs, and between the cells. Sugar, composed of carbon, hydrogen, and oxygen, is found in the blood, Hver, and tissues. Lime, composed of calcium and oxygen, is found in the bone, blood, and nerves. Salt, composed of sodium and chlorine, is found in the tissues and fluids of the body. Iron is found in the haemoglobin of the red blood corpuscles, and gives them power to carry oxygen to all the cells of the body.

Occurrence in Foods. — All foods which we eat, whether animal or vegetable, are also compounds of some of the thirteen elements united in different forms and proportions. Proteins contain carbon, hydrogen, oxygen, nitrogen, and sulphur. Carbohydrates contain carbon, hydrogen, oxygen. Fats contain carbon, hydrogen, and oxygen. Water contains hydrogen and oxygen. The mineral matter occurs in combination with the organic substances, as proteins and carbohydrates. These foods are taken into the body through the mouth and carried to the stomach and intestines, where they undergo chemical change and are reduced to a soluble form, so that they can enter the blood and be carried to the cells, where they are made into the tissues of the body or are oxidized for energy.

The only way that the body can receive the materials out of which to build its tissues, supply the energy needed for living, and secure enough heat to maintain normal temperature, is through the food eaten. These demands of the body must be supplied, or the health and the working efficiency of the individual are impaired. For these reasons, it is of the utmost importance that all people should have some knowledge of the composition of the various foods and what elements they will supply. The best example of the service such knowledge would render to the individual can be seen from the fact that growing girls are subject to anemia, a disease or condition due to the lack of iron in the red blood corpuscles. Almost the only way that the human body can assimilate iron is when it is in combination with some organic substance, as in food. A study of foods would show which contain the desired iron, and the diseased or abnormal condition could be readily remedied.

Another example which shows the importance of this knowledge is furnished by the fact that if any element is not supplied in the right proportions needed for all the vital processes and tissues, the amount supplied is first used for the vital processes, and the tissues suffer. Moreover, if not enough is supplied for the vital processes, it is taken from the tissues, and they are weakened to that extent. Lime, for instance, is needed for bone, nerve, and muscle. It is also needed in the blood and digestive ferments, and will be taken first by the blood and ferments. The result of an insufficient supply would be soft bones, twitching nerves, or flabby muscles. Lime is needed for infants and growing children in much greater abundance than for those who have attained growth, and mothers should know what foods supply an abundance of lime.

Chemical Change or Action. — In various substances the elements are held together more or less loosely, so that if two substances are brought together, the elements tend to separate and unite again with other elements to form new and more stable substances. This is called chemical change or action, and is constantly going on, transforming inert waste substances into plants and animals, and breaking down living matter into hfeless matter. Plants take in carbon dioxide, — a waste substance given off by animals, — water, and mineral matter, and from them construct starch and other substances found in plants. Certain bacteria feed on living matter, as tissues in the human body, and decompose it. Yeast plants break down sugar and change it into alcohol and carbon dioxide. Iron has a strong attraction for the oxygen in the air. In the presence of moisture, the iron unites with the oxygen, forming a new substance called oxide of iron or iron rust.

Probably the most familiar example of chemical change is the one usually cited because of its similarity to the chemical change which takes place in the body when foods are oxidized. That is, the burning of any fuel outside the body, as wood.

Wood is composed of carbon, hydrogen, oxygen, and mineral matter. When air is present, and the wood is brought to the kindling point, the carbon in the wood unites with the oxygen in the air, forming carbon dioxide (CO2), and the hydrogen and the oxygen unite to form water (H2O). The mineral matter remains in the form of ash. In this way, from wood and air are formed two new substances unlike either of them, carbon dioxide and water. These are the products of combustion, and they are formed whenever a substance containing carbon is burned. Whenever chemical change takes place, energy is involved.

Heat is a form of energy. Any form of energy can be changed into another form without loss. Thus, electric energy may be transformed into light, power, or heat. The energy of burning coal may be used to run an engine or heat a train. When any substance is burned, energy is released as heat. Different substances yield different amounts of energy, — a pound of coal will yield more energy than a pound of wood ; a pound of fat will yield more energy than a pound of sugar. The unit for measuring heat is called the calorie. It is the amount of heat that would be required to raise i pound of water 4° F. ; it is equivalent to the amount of energy required to raise i ton 1.54 feet.

Oxidation. — Oxidation is the name given to one of the chemical changes which take place in the cells of the body. The red corpuscles of the blood carry oxygen to the cells. The plasma of the blood carries albumin, fat, and sugar to the cells. This oxygen unites with the cells and the substances brought by the plasma, and slowly burns or oxidizes them, producing as much energy as these substances would yield if burned outside the body. Some of this energy manifests itself in the form of heat, and is used to maintain the normal temperature of the body (98.6° F.). Some of the energy enables the body to carry on its vital processes.

Oxidation is necessary for the life and growth of the cell. It is the process by which the old cells are broken down so that new ones may be rebuilt. The cells are built from the albumin and mineral matter brought to them in the plasma. The breaking down of the old cells and the building of the new is called metabolism, and it includes also the production of energy during oxidation of the organic material brought to the cells. These processes are inseparable because we should consider the fat and sugar as fuel needed for carrying on the work of upbuilding and repairing of cells, though the building material must be protein.

By oxidation of foods, energy is produced ; but by this oxidation or chemical change of food, new substances are formed called end products, and these products must be eliminated, as the body has no further use for them.

By oxidation of fats and sugar, carbon dioxide and water are produced. By oxidation of albumin, carbon dioxide, water, and the nitrogenous waste, urea, are produced. These waste products are eliminated through the lungs, skin, and kidneys.

The food as it is taken into the body must go through a series of changes before it can be taken into the blood and carried to the cells. This process is called digestion, and will be considered in another chapter. Metabolism includes the changes which take place in the cells,, as distinguished from the changes which take place in the digestive tract.

Chapter II

CLASSIFICATION OF FOODS. OCCURRENCE AND USES

NITROGENOUS FOODS.

I. True Proteins.

Build tissue and yield energy.

All coagulated by heat or acid or ferment.

Coagulation temperatures.

Heat about 165° F.

Ferment 98.6° F.

Forms of Protein Albumin in egg.

Soluble in cold water.

Fibrin in meat.

Myosin in meat.

Soluble in dilute salt solution.

Casein in milk.

Soluble in dilute alkali.

II.

IV. Albuminoids

Do not build tissue, but yield energy.

Softened and dissolved by hot and boiling water.

Form gelatin on cooling.

Hardened by heat and evaporation.

Extractives.

Neither build tissue nor yield energy.

Stimulate, and aid in the assimilation of proteins.

Gluten in wheat.

Legumin in beans.

Forms of Albuminoids Elastin in cell walls.

Ossein in bone.

Collagen in connective tissue.

Forms of Extractives

Kreatin, xanthin, etc.

Products of decomposition of muscle tissue.

Found in meats and some vegetables.

Nitrogenous Fats.

Lecithins, peculiar nitrogenous fats found in different cells of the body, as brain, nerves, liver.

Nitrogenous Foods. — The proteins, or albumins, as they are sometimes called, are the most important of all foods because they form the essential part of the protoplasm of every cell of the body. The same might be said of such mineral substances as phosphorus and iron, but these occur in combination with the various proteins, as nucleoprotein, chromoprotein, etc. All life originates in a single cell ; all tissues and organs are collections of cells. The cell then constitutes the unit of all animal and vegetable life. The cell consists of a tiny mass of protoplasm, — a jellyhke substance, more or less granular, having in the center a denser mass called the nucleus. Cells differ according to their various functions, but all cells are composed of 80 to 85 per cent water, a small amount of mineral matter, and proteins.

The proteins are albumins, globulins, but mostly compound proteins as nucleoprotein, chromoprotein, and lecithoprotein.

It can be said, then, that the proteins are the most important of all foods because they form the essential part of the tissues in the body, and occur in the blood, lymph, and all secretions.

Proteins are also oxidized in the body and furnish energy for work and activity.

The chemical formula of proteins is only approximately known ; very Httle is known of their molecular structure ; there is no universal agreement as to name, and no uniform class?hcation, because physiological chemistry is adding to our knowledge of their differences from day to day. No field of study furnishes more interesting and valuable research, information, and data.

Chittenden has defined protein as a substance which contains carbon, hydrogen, oxygen, nitrogen, and sulphur, — the nitrogen being in a form to serve the physiological needs of the body. That is, in such form that it will build tissue.

The proteins contain about i6 per cent nitrogen, though the amount varies from 15J per cent to 19 per cent. The compound proteins contain phosphorus, also. Some contain iron and other elements. For the purpose of study nitrogenous foods may be classified as True Proteins, Albuminoids, and Extractives (see page 18), but to get even a faint idea of the uses of the various foods as nutrients for the body, famiharity with the general classification of proteins is necessary. For example, wheat flour as commonly purchased is made from the part of the wheat that contains the protein in the form of glutelin ; the germ and outer coats, removed in milling, contain different proteins, as nucleoprotein and others. If, even in a grain of wheat, the character of the protein varies in the different parts because each part has different work in the growth and development of the young plant, it is evident that man should have some knowledge of the different proteins to know which foods contain those needed for the growth and development of his various tissues and organs.

True proteins, as classified on page 18, or simple, derived and compound proteins as classified on page 34, contain nitrogen in a form to serve the physiological needs of the body for tissue building. They also furnish energy. •No one of these proteins mil build all kinds of tissue, however. An erroneous idea prevails that any form of protein is as good as several forms. That this is not true is seen from experiments where animals have been fed on one kind of protein and the deteriorating effects of such diet noted. It is also seen in the evil effects of excessive consumption of meat.

It may be said that the opinion is gaining ground that it is not the quantity of protein consumed that is harmful, but the kind of protein. It might be added also, that it is the lack of certain mineral ingredients in some proteins.

Albuminoids do not contain nitrogen in the form to serve the physiological needs of the body for tissue building, but they yield energy. For this reason they are spoken of as protein sparers, because if other foods are used as sources of energy, the proteins can be used simply for tissue building. Extractives are decomposition products of muscle tissue or proteins, and neither build tissue nor yield energy. They furnish flavor to meat, act as stimulants to appetite, and call out the digestive juices.

The commonest proteins in food are albumin as found in egg and blood, casein in milk, glutens in wheat, legumin in peas and beans, fibrin and myosin in meat. Under the action of certain ferments normally present, they assume shghtly different form and composition. Ferments change hquid myosinogen, fibrinogen, and caseinogen to the coagulated forms myosin, fibrin, and casein. Foods containing the most proteins are cheese, legumes, meat, fish, egg, milk, and cereals.

The true proteins are all coagulated by heat or acid or ferment and rendered less easily digestible. The higher the temperature at which they are coagulated, the harder they are to digest. Proteins cannot diffuse through animal membrane and are changed during digestion from insoluble proteins to a soluble form, — peptone, — and in that form they enter the blood. They are used in the body to build tissue and yield energy, and in this process they are broken down into simple compounds, their ultimate products of decomposition being the nitrogenous wastes, carbon dioxide, and water.

The proteins are being constantly decomposed or broken down in the body as a result of cell activity. If these decomposition products are not immediately removed from the cells, they act as poisons or toxins, producing fatigue or pain or lowering the vitality. These products are normally removed through the kidneys in the form of urea, and it will be readily seen that if more protein is consumed than is needed for tissue renewal, it either accumulates in the tissues, or is not fully oxidized to urea, and intermediate products are formed that may be harmful to the body, or may impose extra work on the excretory organs.

Too much importance cannot be given to the fact that the system must rid itself of waste products, or they accumulate and lower resistant power or working efhciency. It is because the decomposition products of protein metaboKsm are so harmful if not neutralized, or if not fully oxidized, that so much is written concerning excessive consumption of protein foods.

Albuminoids occur in the various animal tissues. All forms of connective tissue, such as the cell walls and the substance that holds cells together, are albuminoids. The common forms are : elastin in cell walls ; ossein in bone ; collagen in tendons and ligaments. The albuminoids are hardened by heating and drying, but are softened and dissolved by heat and moisture, and when cooled, form gelatin. This knowledge of the action of heat on cell walls and connective tissue is of great value in the cooking of meats and fish. By boiling meat in water the cell walls and the substance holding the cells together are dissolved, the protein inside the cells is coagulated and toughened, and the result is a stringy mass of fibers. This condition can be avoided by cooking the meat at a temperature that will soften, but not dissolve, the connective tissue. This connective tissue is so delicate in most fish that the flesh will fall apart if the fish are boiled.

Extractives, as kreatin, kreatinin, xanthin, are found in meat juice and meat extract, also in some vegetables, as asparagin in potato. They are soluble in hot and cold water and are often lost in cooking. They give to meat its flavor. Those meats, like beef and mutton, having the greatest amount of flavor contain more extractives than veal, pork, and chicken.

Extractives are present in greatest quantity in muscles that are exercised most ; game has more than tame fowl.

Extractives neither build tissue nor yield energy, but act as'stimulants to digestion, and they may aid in the digestion of proteins.

Lecithin is a peculiar nitrogenous fat, containing phosphorus, found in nerves, brain, and bile. Combined with albumin it forms lecithoprotein and is found in the lungs and liver. In foods it is found principally in milk and eggs and in the seeds of plants.

B. NON-NITROGENOUS FOODS.

I. Carbohydrates. Forms of Carbohydrates

Softened by heat or acid i. Starch. As in potato, rice, or ferment. corn, and all other vege-