The starches can be digested only after they are turned into sugars in the body. If you put salt with sugar or starch, although it will mix perfectly and give its taste to the mixture, neither the salt nor the starch nor the sugar will have changed at all, but will remain exactly as it was in the first place, except for being mixed with the other substances. But if you were to pour water containing an acid over the starch, and then boil it for a little time, your starch would entirely disappear, and something quite different take its place. This, when you tasted it, you would find was sweet; and, when the water was boiled off, it would turn out to be a sugar called glucose. Again, if you should pour a strong acid over sawdust, it would “char” it, or change it into another substance, carbon. In both of these cases—that of the starch and of the sawdust—what we call a chemical change would have taken place between the acid and the starch, and between the strong acid and the sawdust.

If we looked into the matter more closely, we should find that what has happened is that the starch and the sawdust have changed into quite different substances. Starches are insoluble in water; that is, although they can be softened and changed into a jelly-like substance, they cannot be completely melted, or dissolved, like salt or sugar. Sugar, on the other hand, is a perfectly soluble or “meltable” substance, and can soak or penetrate through any membrane or substance in the body. Therefore all the starches which we eat—bread, biscuit, potato, etc.—have to be acted upon by the ferments of our saliva and our pancreatic juice, and turned into sugar, called glucose, which can be easily poured into the blood and carried wherever it is needed, all over the body. Thus we see what a close relation there is between starch and sugar, and why the group we are studying is sometimes called the starch-sugars.

The starches are valuable and wholesome foods. They form the largest part, both in bulk and in fuel value, of our diet, and have done so ever since man learned how to cultivate the soil and grow crops of grain. The reason is clear: One acre of good land will grow from ten to fifteen times the amount of food in the form of starch in grains or roots, as of meat in the shape of cattle or sheep. Consequently, starch is far cheaper, and this is its great advantage.

Our chief supply of starch is obtained from the seed of certain most useful grasses, which we call wheat, oats, barley, rye, rice, and corn, and from the so-called “roots” of the potato. Potatoes are really underground buds packed with starch, and their proper name is tubers.

Starch, when pure or extracted, is a soft, white powder, which you have often seen as cornstarch, or laundry starch. As found in grains, it is mixed with a certain amount of vegetable fibre, covered with husks, or skin, and has the little germ or budlet of the coming plant inside it. It has been manufactured and laid down by little cells inside their own bodies, which make up the grains; so that each particular grain of starch is surrounded by a delicate husk—the wall of the cell that made it. This means that grains and other starch foods have to be prepared for eating by grinding and cooking. The grinding crushes the grains into a powder so that the starch can be sifted out from the husks and coating of the grain, and the fibres which hold it together; and the cooking causes the tiny starch grain to swell and burst the cell wall, or bag, which surrounds it.

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The risks from tainting or spoiling are particularly great in the case of milk, partly on account of the dusty and otherwise uncleanly barns and sheds in which it is often handled and kept, and from which it is loaded with a heavy crop of bacteria at the very start; and partly because the same delicateness which makes it so easily digestible for babies, makes it equally easy for germs and bacteria to grow in it and spoil, or sour, it. You all know how disagreeable the taste of spoiled milk is; and it is as dangerous as it is disagreeable. A very large share of the illnesses of babies and young children, particularly the diseases of stomach and bowels which are so common in hot weather, are due to the use of spoiled, dirty milk.

There is one sure preventive for all these dangers, and that is absolute cleanliness from cow to customer. All the changes that take place in milk are caused by germs of various sorts, usually floating in the air, that get into it. If the milk is so handled and protected, from cow to breakfast table, that these germs cannot get into it, it will remain sweet for several days. Boards of Health all over the world now are insisting upon absolutely clean barns and cleanly methods of handling, shipping, and selling milk. In most of our large cities, milk-men are not allowed to sell milk without a license; and this license is granted only after a thorough examination of their cattle, barns, and milk-houses. These clean methods of handling milk cost very little; they take only time and pains. (http://thehumanhealth.wordpress.com)

The starches contain no nitrogen except a mere trace in the framework of the grains or roots they grow in. They burn very clean; that is, almost the whole of them is turned into carbon dioxid gas and water.

This burning quality makes the starches a capital fuel both in the body and out of it. You may have heard of how settlers out on the prairies, who were a long way from a railroad and had no wood or coal, but plenty of corn, would fill their coal scuttles with corn and burn that in their stoves; and a very bright, hot fire it made.

One of the chief weaknesses of the starches is that they burn up too fast, so that you get hungry again much more quickly after a meal made entirely upon starchy foods, like bread, crackers, potatoes, or rice, than you do after one which has contained some meat, particularly fat, which burns and digests more slowly.

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Taken all together, the proteins, or meats, are the most nutritious and wholesome single class of foods. Their chief drawback is their expense, which, in proportion to their fuel value, is greater than that of the starches. Then, on account of their attractiveness, they may be eaten at times in too large amounts. They are also somewhat more difficult to keep and preserve than are either the starches or the fats. The old idea that, when burned up in the body, they give rise to waste products, which are either more poisonous or more difficult to get rid of than those of vegetable foods, is now regarded as having no sufficient foundation. Neither is the common belief that meats cause gout well founded.

The greatest danger connected with meats is that they may become tainted, or begin to spoil, or decay, before they are used. Unfortunately, the ingenious cook has invented a great many ways of smothering, or disguising, the well-marked bad taste of decayed, or spoiled, meat by spices, onions, and savory herbs. So, as a general thing, the safest plan, especially when traveling or living away from home, is to avoid as far as possible hashes, stews, and other “made” dishes containing meat. This is one of the ways in which spices and onions have got such a bad reputation for “heating the blood,” or upsetting the stomach, when it is really the decayed meat which they are used to disguise that causes the trouble. Highly spiced dishes rob you of the services of your best guide to the wholesomeness of food—your nose.

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Several vegetable substances contain considerable amounts of protein. One of these has already been mentioned,—the gluten or sticky part of bread,—and this is what has given wheat its well-deserved reputation as the best of all grains out of which to make flour for human food.

There is also another vegetable protein, called legumin, found in quite large amounts in dried beans and peas; but this is of limited food value, first because it is difficult of digestion, and secondly because with it, in dried peas and beans, are found a pungent oil and a bitter substance, which give them their peculiar strong flavor, both of which are quite irritating to the average person’s digestion. So distressing and disturbing are these flavoring substances to the civilized stomach, that, after thousands of attempts to use them more largely, it has been found that a full meal of beans once or twice a week is all that the comfort and health of the body will stand. This is really a great pity, for beans and peas are both nourishing and cheap. Nuts also contain much protein, but are both difficult of digestion and expensive.

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Soups, broths, and beef teas are water in which meats, bones, and other scraps have been boiled. They are about ninety-eight per cent water, and contain nothing of the meat or bones except some of their flavor, and a little gelatin. They have little or no nutritive or fuel value, and are really Paper foods, useful solely as stimulants to appetite and digestion, enabling us to swallow with relish large pieces of bread or crackers, or the potatoes, rice, pea-meal, cheese, or other real foods with which they are thickened. Their food value has been greatly exaggerated, and many an unfortunate invalid has literally starved on them. Ninety-five per cent of the food value of the meat and bones, out of which soups are made, remains at the bottom of the pot, after the soup has been poured off. The commercial extracts of meat are little better than frauds, for they contain practically nothing but flavoring matters.

Milk is an interesting food of great value because it combines in itself all three of the great classes of food-stuffs,—protein, starch-sugar, and fat. Its protein is a substance called casein, which forms the bulk of curds, and which, when dried and salted, is called cheese. The fat is present in little tiny globules which give milk its whitish or milky color. When milk is allowed to stand, these globules of fat, being lighter, float up to the top and form a layer which is called cream. When this cream is skimmed off and put into a churn, and shaken or beaten violently so as to break the little film with which each of these droplets is coated, they run together and form a yellow mass which we call butter. In addition to the curd and fat, milk contains also sugar, called milk-sugar (lactose), which gives it its sweetish taste. And as a considerable part of the casein, or curd, is composed of another starch-like body, or animal starch, this makes milk quite rich in the starch-sugar group of food-stuffs.

All these substances, of course, in milk are dissolved in a large amount of water, so that when milk is evaporated, or dried, it shrinks down to barely one-sixth of its former bulk. It is, in fact, a liquid meat, starch-sugar, and fat in one; and that is why babies are able to live and thrive on it alone for the first six months of their lives. It is also a very valuable food for older children, though, naturally, it is not “strong” enough and needs to be combined with bread, puddings, meat, and fat.

Weight for weight, most of the butcher’s meats—beef, pork, mutton, and veal—have about the same food value, differing chiefly in the amount of fat that is mixed in with their fibres, and in certain flavoring substances, which give them, when roasted, or broiled, their special flavors. The different flavors are not of any practical importance, except in the case of mutton, which some people dislike and therefore can take only occasionally, and in small amounts.

The amount of fat in meats, however, is more important; and depends largely upon how well the animal has been fed. There is usually the least amount of fat in mutton, more in beef, and by far the greatest amount in pork. This fat adds to the fuel value of meat, but makes it a little slower of digestion; and its presence in large amounts in pork, together with the fact that it lies, not only in layers and streaks, but also mixed in between the fibres of the lean as well has caused this meat to be regarded as richer and more difficult of digestion than either beef or mutton. This, however is not quite fair to the pork, because smaller amounts of it will satisfy the appetite and furnish the body with sufficient fuel and nutrition. If it be eaten in moderate amounts and thoroughly chewed, it is a wholesome and valuable food.

Veal is slightly less digestible than beef or mutton, on account of the amount of slippery gelatin in and among its fibres; but if well cooked and well chewed, it is wholesome.

The other meats—chicken, duck, and other poultry, game, etc.—are of much less nutritive value than either beef, pork, or mutton, partly because of the large amount of waste in them, in the form of bones, skin, and tendons, and partly from the greater amount of water in them. But their flavors make them an agreeable change from the staple meats.

Fish belongs in the same class as poultry and consists of the same muscle substance, but, as you can readily see by the way that it shrinks when dried, contains far more water and has less fuel value. Some of the richer and more solid fishes, like salmon, halibut, and mackerel, contain, in addition to their protein, considerable amounts of fat and, when dried or cured, give a rather high fuel value at moderate cost. But the peculiar flavor of fish, its large percentage of water, and the special make-up of its protein, give it a very low food value, and render it, on the whole, undesirable as a permanent staple food. Races and classes who live on it as their chief meat-food are not so vigorous or so healthy as those who eat also the flesh of animals. As a rule, it is not best to use fish as the main dish of a meal oftener than two or three times a week.

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There are many different kinds of Coal foods, such as pork, mutton, beef, bread, corn-cakes, bacon, potatoes, rice, sugar, cheese, butter, and so on. But when you come to look at them more closely, and to take them to pieces, or, as we say, analyze them, you will see that they all fall into three different kinds or classes: (1) Proteins, such as meat, milk, fish, eggs, cheese, etc. (2) Starch-sugars (carbohydrates), found pure as laundry starch and as white sugar; also found, as starch, making up the bulk of wheat and other grains, and of potatoes, rice, peas; also found, as sugar, in honey, beet-roots, sugar cane, and the sap of maple trees. (3) Fats, found in fat meats, butter, oil, nuts, beeswax, etc.

This whole class of Coal foods can be recognized by the fact that usually some one of them will form the staple, or main dish, of almost any regular meal, which is generally a combination of all three classes—a protein in the shape of meat; a starch-sugar in the form of bread, potatoes, or rice; and a fat in the form of butter in northern climates, or of olive oil in the tropics.

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