CLASSIFICATION OF FOODS
In the previous chapters, we have given the classification of the elements in foods which supply the body needs. Below we classify the foods commonly used, according to the predominance of these elements.
Carbonaceous Foods
While all foods contain a combination of elements, the foods described below contain a greater proportion of carbohydrates and fats, and are classed as carbonaceous.
Roots and Tubers
Of the carbohydrates, next in importance to the sugars and to the starches in their purest form (corn starch, tapioca, sago, and arrowroot), come the roots and tubers, such as potatoes, sweet potatoes, beets, parsnips, turnips and onions.
The following table shows the proportion of various foodstuffs in these vegetables:
TABLE I—ROOTS AND TUBERS
| Food Materials | Water Per Cent | Protein Per Cent | Fat Per Cent | Carbohydrates Per Cent | Ash Per Cent | Food Value per pound Calories |
| Sweet Potatoes | 69.4 | 1.5 | 0.3 | 26.2 | 2.6 | 440 |
| White Potatoes | 75.0 | 2.1 | 0.2 | 22.0 | 0.7 | 295 |
| Parsnips | 64.4 | 1.3 | 0.4 | 10.8 | 1.1 | 230 |
| Onions | 86.0 | 1.9 | 0.1 | 11.3 | 0.7 | 225 |
| Beets | 87.0 | 1.4 | 0.1 | 7.3 | 0.7 | 160 |
| Carrots | 88.2 | 1.1 | 0.4 | 8.2 | 6.0 | 210 |
| Turnips | 92.7 | 0.9 | 0.1 | 0.1 | 0.6 | 120 |
Potatoes. It will be noted from the above table that sweet potatoes have a larger percentage of carbohydrates, hence they produce more heat and energy, than any other vegetable; next to the sweet potato, the Irish potato.
In the above table, the skins of the vegetables are included, and while the white potato contains two per cent protein, this is almost all located in a very thin layer immediately beneath the skin, so that when the potato is peeled in the ordinary way, the protein is removed. This holds true in many vegetables. They lose their distinctive flavor, as well as their value as tissue building foods, when the skins are removed. In baking a potato, the outer skin is readily separated from a less perceptible covering containing the protein, and this second skin should be eaten to get the full value and flavor.
In the white potato, of the twenty-two per cent carbohydrates three and two-tenths per cent is sugar and eighteen and eight-tenths per cent is starch. In the sweet potato, ten and two-tenths per cent is sugar and sixteen per cent is starch. Since sugar digests more quickly than starch, the sweet potato digests more quickly than the white. Because of the large per cent or carbohydrates in each, it is a mistake to serve these two vegetables at the same meal. For the same reason, bread and potatoes should not be eaten, to any extent, at the same meal, unless by one who is doing heavy manual labor, requiring much energy.
Onions. Only about four per cent of the onion represents nourishment; the eleven per cent of carbohydrates is made up of two and eight-tenths per cent sugar and the rest extractives. Of the extractives the volatile oil, which causes the eyes to water when peeling, is the most important. The onion is not, therefore, so important for its actual nourishing qualities as for its relish and flavor, and for this it is to be commended. It is a diuretic, encouraging a free action of the kidneys. Because of its diuretic value it is commonly called a healthy food. An onion and lettuce sandwich stimulates the action of the kidneys and is a nerve sedative.
The volatile oil makes the onion difficult for some to digest and, in that case, should be omitted from the diet.
Beets. There is no starch in beets, the seven and three-tenths per cent carbohydrates being sugar; they possess, therefore, more nutritive value than onions, and they are easily digested. It will be noted that it takes many beets to make a pound of sugar.
There are no more delicious nor nutritive greens than the stem and leaf of the beet. These greens contain much iron and are valuable aids in building up the iron in the blood, thus correcting anaemia.
Carrots. Carrots are valuable as food chiefly on account of their sugar. They are somewhat more difficult of digestion than beets and they contain more waste. They make a good side dish, boiled and served with butter or cream.
Turnips. Turnips have little value as a food. Their nutriment consists in the sugar they contain. For those who enjoy the flavor they are a relish, serving as an appetizer, and, like the onion, are to be recommended as a side dish for this purpose.
Parsnips. Like carrots, parsnips are chiefly valuable for their sugar and for the extractives which act as appetizers.
Since turnips, carrots, onions, and parsnips owe a part of their value in nutrition to the extractives which whet the appetite for other foods, it follows that, if one does not enjoy the flavor or the odor, these vegetables lose in value to that individual as a food. If one does enjoy the flavor, it adds to their food value.
Green Vegetables
The question may be asked with reason: “Why do we eat green vegetables?” They contain only about four per cent nutrition, as will be seen by the chemical analysis in the following table, and are mostly made up of water and pulp. It will be noted from the table that they are distinctly lacking in protein (nitrogenous matter) and in carbohydrates; hence, they have little food value. Some of them have strong acids, thus increasing the alkalinity of the blood.
Their merit lies in the fact that they have distinct flavors and thus whet the appetite. Another reason why green vegetables are thoroughly enjoyed is because they come fresh in the spring, when the appetite is a little surfeited with the winter foods and one looks for green things.
TABLE II—GREEN VEGETABLES
| Food Materials | Water per cent | Nitrogenous Matter per cent | Fat per cent | Carbohydrates per cent | Mineral Matter per cent | Cellulose per cent | Fuel Value per pound Calories |
| Cabbage | 89.6 | 1.80 | 0.4 | 5.8 | 1.3 | 1.1 | 165 |
| Spinach | 90.6 | 2.50 | 0.5 | 3.8 | 1.7 | 0.9 | 120 |
| Vegetable Marrow | 94.8 | 0.06 | 0.2 | 2.6 | 0.5 | 1.3 | 120 |
| Tomatoes | 91.9 | 1.30 | 0.2 | 5.0 | 0.7 | 1.1 | 105 |
| Lettuce | 94.1 | 1.40 | 0.4 | 2.6 | 1.0 | 0.5 | 105 |
| Celery | 93.4 | 1.40 | 0.1 | 3.8 | 0.9 | 0.9 | 85 |
| Rhubarb | 94.6 | 0.70 | 0.7 | 2.3 | 0.6 | 1.1 | 105 |
| Water Cress | 93.1 | 0.70 | 0.5 | 8.7 | 1.3 | 0.1 | 110 |
| Cucumbers | 95.9 | 0.80 | 0.1 | 2.1 | 0.4 | 0.5 | 10 |
| Asparagus | 91.7 | 2.20 | 0.2 | 2.9 | 0.9 | 2.1 | 110 |
| Brussels Sprouts | 93.7 | 1.50 | 0.1 | 3.4 | 1.3 | 0.4 | 95 |
| Beans (string) | 8.92 | 2.3 | 0.3 | 7.4 | 0.8 | 7.0 | 195 |
| Beans (dried) | 12.6 | 22.5 | 1.8 | 59.6 | 3.5 | 0.0 | 1605 |
| Peas (green, shelled) | 74.6 | 7.0 | 0.5 | 16.9 | 1.0 | 0.0 | 465 |
All fresh vegetables should be masticated to almost a fluid consistency; otherwise, they are difficult of digestion, containing, as they do, so much pulp.
They are diuretic, helping the kidneys and the skin to rid the system of waste, and they are more laxative to the intestines than the root vegetables, partly because of the salts which they contain and partly because of the undigested vegetable fibre, which helps to move along the waste in the intestines. This vegetable fibre, being coarse, assists in cleansing the mucous lining of stomach and intestines, and, if for no other reason than for this cleansing of kidneys and intestines in the spring, when the system is most sluggish, the use of green vegetables is to be commended.
In larger cities, fresh vegetables are in the markets the year around, but if they are raised in greenhouses, or in any way forced, they lack the matured flavor and they also lack the iron which the rays of the sun give. If raised in the south and shipped for a distance, they are not fresh and they do not have as good an effect upon the system as when fresh and fully matured by the sun.
All greens, as spinach, chard, dandelions and beet tops, as previously stated, contain iron and build red blood corpuscles.
It is well, then, to eat freely of fresh vegetables in their season, even though they do not appreciably build tissue or furnish energy. By their effect upon the blood, the kidneys, skin, and intestines, they make sluggish vital organs more efficient.
Tomatoes and rhubarb are often, and with reason, classed under fruits.
Fruits
Technically speaking, fruits include all plant products which bear or contain a seed. They are valuable for their acids and organic salts—citrates, malates, or tartrates of potassium, sodium, magnesium, and calcium. In the juices of citrous fruits, are citrates of above minerals.
The fruit juices are readily absorbed and carried at once to the liver, where the sodium, magnesium, and potassium are released and the acids oxidized and changed to carbonates. They increase the alkalinity of the blood. These alkalis are soon eliminated through the kidneys, which accounts for the diuretic effect of fruits.
The seeds in the small fruits are not digested, but they serve the purpose of increasing intestinal peristalsis and of assisting the movement of the contents of the intestines. The skin and the fibre of fruits also assist the intestines in this way, just as the fibre in vegetables does. Fruits may be classified into acid and sweet fruits. Under acid fruits are the citrous group—lemons, limes, grape fruit, oranges, cranberries, gooseberries, whortleberries, pineapples, currants, and rhubarb—if rhubarb is to be classed as a fruit.
There has been a commonly accepted theory that where a blood test shows evidence of too much uric acid, acid fruits are to be avoided, but the reverse is true. It has been fully demonstrated that the use of acid fruits increases the alkalinity,—or neutralizes the acids in the blood.
In case of an excess of hydrochloric acid in the stomach, lemon, or citrous fruits are valuable about half an hour before a meal as they decrease the secretion of the hydrochloric acid into the stomach. Where hydrochloric acid is limited, acids are given after a meal to supplement the deficient amount.
The sweetening of acid fruits does not detract from the value of the acids or of organic salts.
All acid fruits stimulate the action of the kidneys and the skin,—particularly lemons, limes, grape fruit, and oranges, and wherever the kidneys and skin are not sufficiently active, these fruits should be eaten freely.
It is difficult to make a decided distinction between sweet and acid fruits. The best guide is in the amount of sugar required to make them palatable. Some species of cherry are distinctly sour, while others are sweet. The same is true of apples, peaches, plums, etc.
Under sweet or bland fruits are pears, raspberries, grapes, bananas, blackberries, blueberries, melons, apricots, and some peaches, apples, and plums.
The large majority of fruits do not contain sufficient sugar to make them valuable for nourishment. Their chief value is in their appetizing flavor, and in the acids, and salts. Dates, figs, prunes, and dried grapes (raisins) are exceptions. As will be noted by the following table, these fruits contain a large amount of carbohydrates in the form of sugar. The larger amount of protein in these sweet fruits is largely in the seeds and, as the seeds are not digested, they have no real food value to the individual.
Figs and prunes are laxative,—probably the laxative effect of figs is due to the seeds, and of prunes to the salts and acids. However, prunes are free from tannic acid.
TABLE III—FRUITS
| Food Materials | Water Per Cent | Protein Per Cent | Ether Extract Per Cent | Carbohydrates Per Cent | Ash Per Cent | Cellulose Per Cent | Acids Per Cent | |
| Acid: | ||||||||
| Apples | 82.50 | 0.40 | 0.5 | 12.5 | 0.4 | 2.7 | 1.0 | |
| Apricots | 85.00 | 1.10 | 0.6 | 12.4 | 0.5 | 3.1 | 1.0 | |
| Peaches | 88.80 | 0.50 | 0.2 | 5.8 | 0.6 | 3.4 | 0.7 | |
| Plums | 78.40 | 1.00 | 0.2 | 14.8 | 0.5 | 4.3 | 1.0 | |
| Cherries | 84.00 | 0.80 | 0.8 | 10.0 | 0.6 | 3.8 | 1.0 | |
| Gooseberries | 86.00 | 0.40 | 0.8 | 8.9 | 0.5 | 2.7 | 1.5 | |
| Currants | 85.20 | 0.40 | 0.8 | 7.9 | 0.5 | 4.6 | 1.4 | |
| Strawberries | 89.10 | 1.00 | 0.5 | 6.3 | 0.7 | 2.2 | 1.0 | |
| Whortleberries | 76.30 | 0.70 | 3.0 | 5.8 | 0.4 | 12.2 | 1.6 | |
| Cranberries | 86.50 | 0.50 | 0.7 | 3.9 | 0.2 | 6.2 | 2.2 | |
| Oranges | 86.70 | 0.90 | 0.6 | 8.7 | 0.6 | 1.5 | 1.8 | |
| Lemons | 89.30 | 1.00 | 0.9 | 8.3 | 0.5 | 1.5 | 1.8 | |
| Pineapples | 89.30 | 0.04 | 0.3 | 9.7 | 0.3 | 1.5 | 7.0 | |
| Pears | 83.90 | 0.40 | 0.6 | 11.5 | 0.4 | 3.1 | 0.1 | |
| Blackberries | 88.90 | 0.90 | 2.1 | 2.3 | 0.6 | 5.2 | 1.6 | |
| Raspberries | 84.40 | 1.00 | 2.1 | 5.2 | 0.6 | 7.4 | 1.4 | |
| Mulberries | 84.70 | 0.30 | 0.7 | 11.4 | 0.6 | 0.9 | 1.8 | |
| Grapes | 79.00 | 1.00 | 1.0 | 15.5 | 0.5 | 2.5 | 0.5 | |
| Watermelons | 92.90 | 0.30 | 0.1 | 6.5 | 0.2 | 1.0 | 0.5 | |
| Bananas | 74.00 | 1.50 | 0.7 | 22.9 | 0.9 | 0.2 | 0.5 | |
| Sweet: | ||||||||
| Dates, dried | 2.08 | 4.40 | 2.1 | 65.1 | 1.5 | 5.5 | 7.0 | |
| Figs, dried | 2.00 | 5.50 | 0.9 | 62.8 | 2.3 | 7.3 | 1.2 | |
| Prunes, dried | 2.64 | 2.40 | 0.8 | 66.2 | 1.5 | 7.3 | 2.7 | |
| Raisins | 10.60 | 2.50 | 4.7 | 74.7 | 3.1 | 1.7 | 2.7 | |
Care should be exercised in selecting ripe fruits and those which have not started to decay. The difficulty with so many fruits, which must be shipped from a distance, is, that, in order to reach their destination in fair condition, outwardly, they are picked before ripe and there is too much tannic acid in them. When fruits are allowed to ripen on the trees, the tannic acid is changed to sugar and fruit juices. One test of a ripened apple is to cut it with a steel knife—if the blade turns black, or if the cut surface of the apple turns brown in a few minutes, it should not be eaten, for it indicates an excess of tannin. It is this tannin which gives the small boy, with his green apples, excruciating pains. It will be recalled that the tannin from the bark of trees, so toughens the elastic skin of animals that we can wear this skin for shoes. The effect upon the live skin of the stomach and intestines, from the tannin in food, is not pronounced in toughening the skin, because of the activity and resistance of live matter.
Bananas are commonly picked green, because they decay so quickly that if they were picked ripe they would spoil before reaching the northern markets. The above table shows that bananas contain nearly twenty-three per cent of carbohydrates, which, in an immature state, are largely starches. The natural ripening process changes the starch to sugar, thus making them more easily digested. The starch globules, when not matured on the tree, are not easily broken and are thus difficult of digestion. Baking breaks the globules; a baked banana is thus more readily digested.