Dietaries, Part 2

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

(Page 3 of 11)

Of course the full amount of calories was kept up; as each succeeding quantity of the Protein was left off, it was replaced by a proper quantity of non-nitrogenous food. These experiments were carried out in the usual approved scientific manner. It may, however, be urged against any generalized and positive conclusions as to the minimum quantity of Protein required for the body, being drawn from such experiments, that the period covered by them was much too short.

A prolonged trial might have revealed some obscure physiological derangement. We are quite justified in concluding that the usual, so-called "standard dietaries" contain an unnecessarily large proportion of Protein. In some practical dietaries, 50 grams and under have seemed enough; but for the ordinary adult man, who has been accustomed to an abundance of Protein, and whose ancestors have also, it is probably advisable not to take less than 70 or 80 grams per day. If it is desired to try less, the diminution should be very gradual, and a watch should be kept for any lessening of strength.

Some comments may now be made upon the table of dietaries. That of the London sewing girl contained 53 grams of Protein, which should have been ample, according to some of the authorities we have given; yet she was badly nourished. The food was doubtless of bad quality, and it appears deficient in carbohydrates; this latter is shown by the low number of calories. The long hours and unhealthy conditions of work, and not a deficiency of food constituents, is probably the cause of the bad health of such persons. There is no reason to think the Protein insufficient, although some persons have said as much. We have no pjoints of the German vegetarians, but the calories appear satisfactory. In the poor German laborer's family the calories are too low. In Dr. T.R. Allinson's experiment on a wheat meal dietary, it will not do to assume that less than 82 grams of Protein would have been insufficient. It is probable that a smaller quantity of Protein would have been enough if the fat and carbohydrates had been increased. The calories are below the usual standard. In the succeeding example the calories are considerably higher, being not far from the usual standard, yet 54 grams of Protein sufficed.

It is a common error to place an undue value on the Proteins to the extent of overlooking the other constituents. Dr. Alexander Haig in "Diet and Food," p. 8, cites the case of a boy aged 10, fed on 2-1/4 pints of milk per day. The boy lost weight, and Dr. Haig is of opinion that the quantity of milk was very deficient in Protein; more than twice as much being required. 2-1/4 pints of milk contain about 45 grams of Protein, whereas, according to the usual figures a boy of this age requires 75 g. This quantity of 45 g. is however, higher, allowing for the boy's age, than that in several of the dietaries we have given in our table. A little consideration will show that Dr. Haig has overlooked the serious deficiency of the milk in the other constituents, which accounts for the boy's loss of weight. The quantity of milk contains only about 160 g. of total solid matter, whilst 400 g. is the necessary quantity. Milk is too rich in Protein matter to form, with advantage, the sole food of a human being. Human milk contains much less in proportion to the other constituents.

The old doctrine enunciated by Justus von Liebig was that Protein matter is the principal source of muscular energy or strength. He afterwards discovered and acknowledged his error, and the subject has since been thoroughly investigated. The makers of meat extracts and other foods, either from their own ignorance of modern research or their wish to take advantage of the lack of knowledge and prejudice of the public, call Protein matter alone nourishment. The carbohydrates and fats are equally entitled to be called nourishment.

Our reason for devoting so much space to the consideration of the quantity of Protein matter required, is that in the opinion of many eminent writers it is the crux of vegetarianism. They have stated that it is impossible to obtain sufficient from vegetable foods alone, without consuming an excessive quantity of carbohydrates. We will summaries the argument as given in Kirke's Physiology, as edited by Morrant Baker, a standard work, and which is repeated in Furneaux's "Animal Physiology," a book which is much used in elementary science schools: "The daily waste from the system amounts to, carbon 4,500 grains, and nitrogen, 300 grains. Now let us suppose a person to feed on bread only. In order to obtain the necessary quantity of nitrogen to repair this waste he would have to eat nearly 4-1/4 lbs. daily.... He would be compelled to take about double the quantity of carbon required in order to obtain the necessary weight of nitrogen....

Next, let us suppose that he feeds on lean meat only. Then, in order to obtain the necessary quantity of carbon, he must eat no less than 6-1/2 lbs. daily.... In this case we notice a similar waste of nitrogen, the removal of which would give an undue amount of work to the organs concerned.... But it is possible to take such a mixed diet of bread and meat as will supply all the requirements of the system, and at the same time yield but little waste material." "A combination of bread and meat would supply much more economically what was necessary ... so that 3/4 lbs. of meat, and less than 2 lbs. of bread would supply all the needful carbon and nitrogen with but little waste. From these facts it will be plain that a mixed diet is the best and most economical food for man; and the result of experience entirely coincides with what might have been anticipated on theoretical grounds only." Professor Huxley, in his "Elementary Physiology" uses almost the same figures and argument.

The adoption of this high Protein or nitrogen figure would lead to some ridiculous conclusions. One writer states that 18 eggs would contain sufficient flesh forming substance for a day's ration, but a very much larger quantity would be required to supply enough carbon. On the other hand, Professor Church says that, no less than 70 lbs. of pears would have to be eaten per day, to supply the necessary quantity of nitrogen; although the carbon would be in excess. The curious may calculate the proper quantity of each that would make a theoretically perfect dietary. People are apt to assume that what they themselves eat, or what their class, race, or nation eat, is the proper and necessary diet; at least as far as the elementary constituents and quantities are concerned.

Manchester the Vegetarian Society, 1905.