Dietaries

The Chemistry Of Food and Nutrition
by A. W. Duncan, F.C.S.

(Page 2 of 11)

The best proportions of Proteins, carbohydrates and fats required for the nourishment of the body has not yet been conclusively decided. The common plan is to average the dietary of large bodies of persons, soldiers and prisoners. These dietaries have been adjusted empirically (the earlier ones at least), and are generally considered as satisfactory. They are chiefly of English and German origin. Another method is to laboriously analyze the food consumed and compare it with the excretions, until a quantity and kind of food is found which is just sufficient to keep the body in equilibrium.

This latter plan is the best, but to be quite satisfactory must be tried on a large number of suitable persons under varying conditions, both of quantity and kind of food. Nearly all the experiments have been made on persons accustomed to a stimulating dietary: their usual food has included a considerable quantity of flesh and alcoholic drinks. Sufficient attention has not been paid to the dietaries of the more abstemious races who partake of little if any flesh food. The standard daily dietary for a man of average weight, doing a moderate amount of work, is variously stated by the best authorities as Proteins from 100 to 130 grams, fat 35 to 125 grams, and carbohydrates 450 to 550 grams. There is a surprising difference of opinion on the amount of fat, but those who give least fat give the largest quantity of carbohydrate and vice-versa.

The nutrient ratio is 1 : 4.9. For scientific purposes, metrical weights and measures are used, instead of the inconvenient English grains, ounces, pounds. A calorie is a measure of the power of a food in generating heat and muscular energy (these two being convertible).

The calories used in food tables are kilo-calories, representing the amount of heat which would raise a kilogram of water 1° Centigrade. This is the same as raising 1 pound weight 4° Fahrenheit. According to the table given, 125 grams of dry Protein are required per day; this contains 20 grams of nitrogen and 62 of carbon. When thoroughly consumed or utilized in the body, the heat or its equivalent in muscular work equals 512 kilo-calories. Proteins have, of course, an additional value as tissue formers. The factors used here, of 4.1 and 9.3, are those commonly employed; but the latest and most reliable research, taking account only of that part of the food which is actually available in the body, gives for Protein and carbohydrate 4 calories, and for fat 8.9 calories.

Fat has a higher food value than the carbohydrates, as 4.1 : 9.3 = 2.27 or 4.0 : 89 = 2.225, according to whether the old or new factors are used. In the table of analyses 2.225 was used. The standard dietary for a woman, or of a boy 14 to 16 years of age, is given as equivalent to eight-tenths that of a man; a child of 10 to 13 six-tenths; of 2 to 5 four-tenths. A man doing hard work requires one-tenth more. The following table gives three standard dietaries, and a few actual ones, in grams per day. The food of persons in easy circumstances, and of working men in the receipt of good wages, approximate to the standard dietaries, except that the fat is higher and the carbohydrates proportionately less. This is due to an abundance of animal food.

A striking instance of abstemiousness is that of Cornaro, a Venetian nobleman, who died in the year 1566 at the age of 98. Up to the age of 40 he spent a life of indulgence, eating and drinking to excess. At this time, having been endowed with a feeble constitution, he was suffering from dyspepsia, gout, and an almost continual slow fever, with an intolerable thirst continually hanging upon him. The skill of the best physicians of Italy was unavailing. At length he completely changed his habits of diet, and made a complete recovery. At the age of 83 he wrote a treatise on a "Sure and certain method of attaining a long and healthful life." He says, what with bread, meat, the yolk of an egg and soup, I ate as much as weighed 12 oz., neither more nor less. I drank 14 oz. of wine. When 78 he was persuaded to increase his food by the addition of 2 oz. per day, and this nearly proved fatal. He writes that, instead of old age being one of weakness, infirmity and misery, I find myself to be in the most pleasant and delightful stage of life. At 83 I am always merry, maintaining a happy peace in my own mind. A sober life has preserved me in that sprightliness of thought and gaiety of humor. My teeth are all as sound as in my youth. He was able to take moderate exercise in riding and walking at that age. He was very passionate and hasty in his youth. He wrote other treatises up to the age of 95.

Kumagara, Lapicque and Breis-acher, have, as the result of their experiments, reduced the quantity of Protein required per 24 hours to 45 grams. T. Hirschfeld states, as the conclusion of his research, that it is possible for a healthy man (in one case for 15 days and in another for 10 days) to maintain nitrogenous balance on from 30 to 40 grams of Protein per day. Labbé and Morchoisne made a dieting experiment during 38 days, upon one of themselves. The Protein was derived exclusively from vegetable food. The food consisted of bread, lentils, haricots, potatoes, carrots, chestnuts, endives, apples, oranges, preserves, sugar, starch, butter, chocolate and wine. At the commencement, the day's food contained 14.1 grams of nitrogen = 89.3 Protein, which was gradually diminished.

On the 7th day 11.6 g. N. = 73.5 g. Protein was reached; during this time less N. was eliminated, indicating that the Protein food was in excess of that required for the wear and tear of the body. As the quantity of nitrogenous food was diminished almost daily, the N. eliminated was found to diminish also. This latter was in slight excess of that absorbed; but when a day or two's time was allowed, without further reduction in the food, the body tended to adjust itself to the demised supply, and there was an approximation of income and expenditure. The smallest quantity of food was reached on the 32nd day with 1.06 N. = 6.7 Protein, which was obviously too little, as 2.19 N. = 13.9 Protein was eliminated. On the 21st day 4.12 N. = 26 Protein was injested, and 4.05 N. was eliminated. The inference drawn from the research is that about 26 grams of Protein per day was sufficient. The weight of the body remained practically constant throughout, and the subject did not suffer inconvenience.

Manchester the Vegetarian Society, 1905.