109. Eggs. Consisting of about two-thirds water and the rest albumen and fat, eggs are often spoken of as typical natural food. The white of an egg is chiefly albumen, with traces of fat and salt; the yolk is largely fat and salts. The yellow color is due partly to sulphur. It is this which blackens a silver spoon. Eggs furnish a convenient and concentrated food, and if properly cooked are readily digested.
110. Fish. Fish forms an important and a most nutritious article of diet, as it contains almost as much nourishment as butcher’s meat. The fish-eating races and classes are remarkably strong and healthy. Fish is less stimulating than meat, and is thus valuable as a food for invalids and dyspeptics. To be at its best, fish should be eaten in its season. As a rule shell-fish, except oysters, are not very digestible. Some persons are unable to eat certain kinds of fish, especially shell-fish, without eruptions on the skin and other symptoms of mild poisoning.
111. Vegetable Foods. This is a large and important group of foods, and embraces a remarkable number of different kinds of diet. Vegetable foods include the cereals, garden vegetables, the fruits, and other less important articles. These foods supply a certain quantity of albumen and fat, but their chief use is to furnish starches, sugars, acids, and salts. The vegetable foods indirectly supply the body with a large amount of water, which they absorb in cooking.
112. Proteid Vegetable Foods. The most important proteid vegetable foods are those derived from the grains of cereals and certain leguminous seeds, as peas and beans. The grains when ground make the various flours or meals. They contain a large quantity of starch, a proteid substance peculiar to them called gluten, and mineral salts, especially phosphate of lime. Peas and beans contain a smaller proportion of starch, but more proteid matter, called legumin, or vegetable casein. Of the cereal foods, wheat is that most generally useful. Wheat, and corn and oatmeal form most important articles of diet. Wheat flour has starch, sugar, and gluten—nearly everything to support life except fat.
Oatmeal is rich in proteids. In some countries, as Scotland, it forms an important article of diet, in the form of porridge or oatmeal cakes.
Corn meal is not only rich in nitrogen, but the proportion of fat is also large; hence it is a most important and nutritious article of food. Rice, on the other hand, contains less proteids than any other cereal grain, and is the least nutritious. Where used as a staple article of food, as in India, it is commonly mixed with milk, cheese, or other nutritious substances. Peas and beans, distinguished from all other vegetables by their large amount of proteids—excel in this respect even beef, mutton, and fish. They take the place of meats with those who believe in a vegetable diet.
113. Non-proteid Vegetable Foods. The common potato is the best type of non-proteid vegetable food. When properly cooked it is easily digested and makes an excellent food. It contains about 75 per cent of water, about 20 per cent of carbohydrates, chiefly starch, 2 per cent of proteids, and a little fat and saline matters. But being deficient in flesh-forming materials, it is unfit for an exclusive food, but is best used with milk, meat, and other foods richer in proteid substances. Sweet potatoes, of late years extensively used as food, are rich in starch and sugar. Arrowroot, sago, tapioca, and similar foods are nutritious, and easily digested, and with milk furnish excellent articles of diet, especially for invalids and children.
Explanation of the Graphic Chart. The graphic chart, on the next page, presents in a succinct and easily understood form the composition of food materials as they are bought in the market, including the edible and non-edible portions. It has been condensed from Dr. W. O. Atwater’s valuable monograph on “Foods and Diet.” This work is known as the Yearbook of the U.S. Department of Agriculture for 1894.
KEY: 1, percentage of nutrients; 2, fuel value of 1 pound in calories. The unit of heat, called a calorie, or gramme-degree, is the amount of heat which is necessary to raise one gramme (15.43 grains) of water one degree centigrade (1.8° Fahr.). A, round beef; B, sirloin beef; C, rib beef; D, leg of mutton; E, spare rib of pork; F, salt pork; G, smoked ham; H, fresh codfish; I, oysters; J, milk; K, butter; L, cheese; M, eggs; N, wheat bread; O, corn meal; P, oatmeal; Q, dried beans; R, rice; S, potatoes; T, sugar.
This table, among other things, shows that the flesh of fish contains more water than that of warm-blooded animals. It may also be seen that animal foods contain the most water; and vegetable foods, except potatoes, the most nutrients. Proteids and fats exist only in small proportions in most vegetables, except beans and oatmeal. Vegetable foods are rich in carbohydrates while meats contain none. The fatter the meat the less the amount of water. Thus very lean meat may be almost four-fifths water, and fat pork almost one-tenth water.