The strict vegetarian takes no animal food and no tubers or foods grown underground, limiting the diet entirely to fruits and vegetables grown in the sunlight. Others live on a diet of fruit and nuts, with milk. In a third class may be placed those who exclude fish, flesh and fowl; and in a fourth those who merely exclude food obtained by the infliction of pain. Those who live on fruit, nuts and milk, are sometimes called fruitarians or nutarians. Those who take a mixed diet of milk, milk products, eggs, vegetables, fruits and nuts are often called lacto-vegetarians.
Cereals, vegetables and fruits differ from animal foods in containing comparatively much carbo-hydrate and little protein. Starch is derived from cereals, bananas and chestnuts. Many fruits are rich in sugar. The animal kingdom supplies man with protein food, and the vegetable kingdom provides carbo-hydrates, except honey, fats being derived about equally from both sources. The carbo-hydrates are stored up as starch and circulate, during the life of the plant, as sugar. In the uncooked state the starch is indigestible, for it is enclosed in envelopes of insoluble cellulose. During cooking the granulose of the starch cell swells and bursts its cellulose envelope. Dry heat dextrinises starch. In some plants, e.g. the sugar-beet, the carbo-hydrate is mainly in the form of sugar. Another carbo-hydrate present, especially in fruits, is pectose or a pectin body. It is convertible into pentose, which is partially assimilable. This body is sometimes called vegetable gum. It causes the jellification of fruit on boiling.
The percentage of carbo-hydrates varies in different vegetables and is highest in the tubers. Much is dissolved out in the process of boiling. Such vegetables should be cooked by steaming.
In the above-mentioned tubers the protein and fat are negligible quantities. Obviously many of them are most innutritious, when boiled in the ordinary way. Ninety per cent of the carbohydrate of the sugar-beet is sugar.
Green vegetables are practically fat-free; contain very little protein, and of that one-tenth is lost in cooking; and contain from 2-8 per cent of carbo-hydrate, of which one-third is lost in cooking. They possess the advantage of being able to take up a great deal of fat on cooking. They are liable to set up intestinal fermentation unless quite fresh. The proteins are not as readily absorbed as animal ones. They are chiefly globulins, soluble in dilute saline solutions and consequently largely dissolved out during cooking.
Extractives are plentiful in vegetables and fruits, chiefly in the form of amides. It is generally asserted that vegetable purins are less injurious than those of animal origin, because they are not combined with the toxic products of decomposition. Of this there is no proof. It is more reasonable to suppose that the evil effects, if any, of the animal purins are due to the decomposition products rather than to the fact that they are of animal origin.
Fats are negligible constituents of vegetables and fruits, except nuts. These, in the dried state, contain a percentage varying from ten in chestnuts to sixty or more in walnuts, filberts and hazel nuts. Olein is the predominant fat. Vegetable fats are apparently quite as nutritious and more digestible than animal fats.
Water is present in huge proportions in green vegetables, many tubers, and almost all the fruits, with the exception of nuts. The proportion is increased by cooking and decreased by drying and compression. The chief feature of the saline constituents is the excess of potassium salts.
5 0-20 0
For practical purposes it is worth while stating roughly the amount of carbo-hydrates in the various fruits.
0-5 per cent. : Blackberry, cranberry.
5-10 „ „ Bilberry, raspberry, peach, water melon, strawberry, currant, gooseberry, orange, lemon, pine-apple, cherry. 10-15 „ „ Mulberry, pear, apricot, apple, greengage, plum. 15-20 „ „ Grape (varies from 10 to 30), nectarine, fig, prune. 20-25 „ „ Banana.
Dried fruits contain still more; a percentage varying from 60 to 75 in dates, figs, prunes, currants and raisins. These are particularly valuable as food.
From half to three-fourths of the carbo-hydrate is in the form of sugar, usually laevulose. Apricots, apples and pine-apple also contain cane sugar. The remainder is in the form of pectin bodies or vegetable gum. The amount of cellulose is variable. The fruits also contain organic acids, in combination with potash, which increase the alkalinity of the blood, and urine.
Bananina is a proprietary food made from bananas. It is a flour, the fibrous portions of the fruit being extracted, and in composition is analogous to rice flour. It contains about one-half per cent of fat, and about half the amount of protein, and rather more carbo-hydrate than is present in wheat flour. A kind of bread is made from it. The richness of nuts in fat has led to the preparation of butter substitutes from them, e.g. albene (9d. per lb.), of which one ounce is said to be equivalent to 1 3/5 oz. of butter; nucoline (6d. per lb.), 1 oz. equal to 1 1/2 oz. butter; vegsu, or vegetable suet; nut butter or nuttolene, equivalent to cream and containing protein; cocoa butter, coco-leum, cocolardo; nucoa and Loder's cacos, substitutes for cocoa butter. Fromm's extract is made from crushed nuts, the cellulose and excess of oil being removed, (price 3s. 6d. per lb.). The percentage composition is : - water 25.3, protein 21.9, fat 31.6, carbo-hydrates and cellulose 83, salts 12.8. Malted nuts contain water 4.5, protein 23.6, fat 20.4, maltose 49.3, salts 22. Nuttose, bromose and nut meal are similar foods.