Page:Popular Science Monthly Volume 66.djvu/457

Rh The average daily quantity of fat required by an adult to keep up healthy nutrition, according to various estimates, is two ounces, and proportionally more during the period of growth, after weaning—from half an ounce to two ounces.

1. A supply of fat, per se, to the blood is essential for histogenesis and for the protection of the tissues, and is also of importance for general use as a source of heat and mechanical force.

2. The carbo-hydrates and albuminoids may supply heat and mechanical force, but they can not take the place of fat in histogenesis and protection of tissue.

3. Fats may be supplied by absorption into the portal system, by absorption into the general lymphatic system, and by absorption into the lacteal system. But the latter is the means by which the principal supply of solid fat is carried into the blood, and is the most important.

4. The mean consumption of oxygen by an adult man of average stature (weight, 150 lbs.), taking ordinary exercise, is about thirty ounces in the twenty-four hours, and the heat evolved by each ounce of oxygen in combining with carbon, hydrogen, etc., is about 350 British units. Hence, 10,000 British units of heat will be evolved every twenty-four hours by the combination of thirty ounces of oxygen with carbon, hydrogen, etc.; therefore, the food of an ordinary adult man under ordinary circumstances, should be such as may, in addition to other purposes, evolve at least 10,000 British units of heat.

5. Practical experience in the dieting of large numbers of men, and other means, have enabled us to establish the fact that such an average man as I have spoken of requires for the maintenance of health, a diet which shall contain about four ounces of plastic material, three ounces of fat and ten ounces of carbohydrates; and, on careful analysis of this diet, we find that it can supply the required 10,000 British units of heat, viz., 2,516 from the plastic, 3,357 from the fat and 4,150 from the carbohydrates, total, 10,023.

Fat, as an article of diet, furnishes the potential force necessary for the conversion of other food material into organic tissue and to maintain the bodily functions.

Professor W. O. Atwater, in one of his most important contributions to the Department of Agriculture, on the nutritive value of foods, in comparing nutrients in respect to their fuel values, their capacities for yielding heat and mechanical power, states that 'a pound of protein lean meat or albumen of egg is just about equivalent to a pound of sugar or starch, and a little over two pounds of either would be required to equal one pound of the fat of meat or butter.'

The mistake commonly made with reference to the use of fat food is, that it is only, or especially, applicable to cold climates—an erroneous inference, the same as that cold is preventive of tuberculosis. That fat is the almost exclusive food in Arctic regions is because other food is not obtainable, not because of the frigid climate. It is necessary food, though not in such excess, at all times and