Of the three great food principles required for human nutrition, protein, fats, and carbohydrates, the nut supplies two--protein and fats in rich abundance, and of very finest quality. The amount of protein found in fruits with very few exceptions is so small as to be insignificant; fats are practically wholly absent from fruits, while sugar and dextrine are abundant. Fruits are thus the natural complement of nuts.
The amount of protein contained in nuts is, with two or three exceptions, small as compared with meats, and even some of the cereals; but the studies of nutrition which have been made within the last score of years by Chittenden and numerous other investigators have clearly established the fact that protein which is chiefly represented in the ordinary bill of fare by lean meat, is needed only in very small amount. If the amount of protein eaten equals ten per cent of the total ration the body will receive an abundant supply of material for repairing its nitrogenous tissues, the only function for which protein is essential. Some nuts, as the pine nut and the peanut, are rich in protein. A pound of pine nuts contains as much protein as a pound and a half of lean meat, besides furnishing the equivalent to two-thirds of a pound of butter. The almond is also rich in protein.
But nuts have another special excellence which is worthy of consideration. Recent researches have shown the paramount importance of vitamines--certain subtle elements which are needed to activate or set in operation various processes within the body which are essential to complete nutrition. The vitamines of rice and other cereals are removed with the bran; hence an exclusive diet of polished rice gives rise to _beriberi_. Meat contains vitamines in very small amounts, for vitamines are produced only by plants. The vitamines found in flesh foods represent only the small residue of the supplies which the animal gathered from the grass, corn and other vegetable products which constitute its food.
Twenty years ago, when the diet of sailors consisted chiefly of salt pork, _scurvy_ was a dread scourge which often disabled whole ship crews and sent many a poor seaman into "Davy Jones' locker." The cooking of animal foods destroys the vitamines which they contain. Infants suffer from scurvy when fed on sterilized or pasteurized milk. There is good reason for believing that _pellagra_ is due to a deficiency of vitamines, which are conspicuously absent from a dietary consisting of "sow belly," molasses, tea, coffee, lard, cornmeal, fine flour and polished rice.