DIETETICS

the science of food and feeding of man in health and in disease. Food is required for building up and repairing ti ues, and also as a fuel to provide heat and energy, and different substances contained in food fulfill these different functions. Food is composed both of organic and of inorganic matter, the former including proteins, albuminous substances (e.g.) the flesh'of meat, white of egg; carbohydrates, sugars and starchy substances, and fats, animal or vegetable fats and oils; while the latter include mineral salts, sodium chloride or common salt, phosphates, etc., and water. The substances which build and repair ti ue are the proteins, the mineral salts, and water; while those which provide heat and energy are the fats, the carbohydrates, and the proteins. The value of any food as nutrition to the body depends on several facts; the proportion of proteins, carbohydrates, and other substances present; the amount of heat it is able to produce; and the proportion of actually nutritive substances it contains, and the ease with which these are absorbed by the ti ues. The amount of food required naturally varies with different individuals under different conditions, but exhaustive investigations show the minimum dietary required by a normal adult man under moderate conditions of muscular work. Such a man excretes 16-20 grammes of nitrogen and about 320 grammes of carbon every day, and the daily amount of nutritive substances required for such a lo is 125 grammes of protein, 500 grammes of carbohydrate, 50 grammes of fat, the sum of which on analysis will be found to contain 20 grammes of nitrogen and 300 grammes of ‘carbon, while the calorimeter shows that it will produce just over 3,000 calories or units of heat. To provide the proper quantied ties of the above substances a mix diet is nece ary, as no single food has the correct proportion, and a suitable daily diet has been shown to be 1 Ib. of bread, 1% Ib. of meat, 14 ib. of fat, 1 Ib. of potatoes, 14 pint of milk, 4 lb. (or 2) eggs, 4% Ib. cheese. A man doing severe muscular work requires a greater amount of food than the above—enough a produce 4,500-5,000 calories. See ‘Oops.