Chittenden's Experiments

Reflecting upon these facts and fully believing in the principle of moderation, Professor Chittenden determined to put the question to the test of scientific experiment. His attention had been directed in 1901 to the mastication experiments of Mr. Horace Fletcher and Dr. Van Someren, who at their own instance had submitted themselves to the observation of Sir Michael Foster with the object of proving the revolutionary contention which they made that the average man was eating twice too much food. They had the gratification of demonstrating that careful mastication had made the appetite more discriminating, had diminished the total requirement of food by one half, and in particular had caused a reduction of the protein ration by quite two-thirds. In 1902-1903 Mr. Fletcher spent several months with Chittenden, and showed that he was able to maintain his body weight of 75 kilos and perform the work of a trained athlete in the gymnasium on about 43 grams of protein.

Being now thoroughly satisfied that the observations of Voit and others on the dietetic habits of the people had failed to establish the true physiological requirements of the body, Chittenden determined to institute a prolonged experiment of his own, and in this he was fortunate in having the cooperation of the United States Government and the Carnegie Institute. His aim was to demonstrate the true nutritive requirements of the body as contrasted with the dietetic habits, and he insisted that during the experiment the following four points should be carefully kept in view: -

(1) That nitrogen equilibrium be maintained, thus ensuring that no excessive acid waste products of protein metabolism were created to irritate the tissues and that no demand was made upon the tissues themselves to produce the nitrogen required for nutrition.

(2) That physiological equilibrium be maintained, i.e., that the body weight should not be reduced.

(3) That physical efficiency be maintained.

(4) That the body should retain its power of resisting disease.

The subjects of the experiments were (1) five brain-workers (University professors and instructors), (2) thirteen men who volunteered from the Hospital Corps of the U.S. Army to represent the moderate muscle-workers, (3) eight University athletes, all thoroughly trained, and who worked hard both mentally and physically. From October, 1903, to June, 1901, 225 days in all, these men submitted to have all their food and drink carefully weighed and measured, their daily excretions analysed, and at stated times their "nitrogen equilibrium" ascertained. On account of the reasons already given, the problem was narrowed down to the discovery of the smallest quantity of protein necessary for nutrition and the maintenance of health.

Results And Observations

It will not be essential to enter into the details of the investigation, which can be read in Chittenden's personal narrative. It is sufficient to record that he himself, a man of 57 kilos body-weight, maintained himself in nitrogenous equilibrium and greatly improved his health on 36 grams of protein, while his total daily diet measured no more than 2,000 calories. Dr. Mendel, who weighed 70 kilos, was responsible for the ingestion of 41 grams of protein per day and food of a total fuel value of 2,500 calories, and the three other brain-workers in like proportion.

The members of the soldier detachment lived without discomfort for a period of five months on amounts of protein food not more than half of that considered necessary by standard dietaries, or about 50 grams, and the average for the athletes was 55 grams. But this dietetic restriction not only succeeded in fulfilling the four principles laid down by Chittenden, but also effected a notable improvement in the health, and their strength was so greatly augmented that dynamometric mensuration recorded an increase of quite 50 per cent.

It will be seen that these results were effected without in any way supplementing the other elements in the diet, and a scrutiny of the items in the menu fails to discover that any restriction was practised as regards the nature of the protein. It is also of importance to note that no kind of food or food-accessory was prohibited or prescribed, although, the object being to live on the smallest possible quantity of protein consistent with health and vigour, flesh foods were naturally reduced to a minimum. There was likewise a noteworthy diminution in the total quantity of the food. Chittenden's whole allowance for the day only weighed 1 pound 6 ounces, about two-thirds of what the average man takes three times a day. The athletes consumed very little more, while the soldiers, instead of their customary 75 ounces of solid food and 3 pints of coffee, took only 51 ounces of solid food and 1 3/4 pints of coffee, and instead of 22 ounces of meat in their former dietary they were now content with only 1 ounce daily. As a result of this experience Chittenden therefore crystallised his views on the dietetic problem in the statement that he believes in a low-protein mixed diet for the following reasons: -

(1) Because he coincides with Folin and others in the view that no nitrogen can be stored up in the tissues.

(2) Because energy is dissipated in excreting the surplus protein.

(3) Because excess of protein tends to disseminate toxins throughout the body.

(4) Because there is no necessity to indulge in muscular exertion to aid in working off surplus protein, and hence energy is saved.

(5) Because a combination of animal and vegetable proteins is essential for the requirements of the body.

There are only two arguments which could be reasonably urged in opposition to these conclusions, and neither of them is tenable: (1) that the excess of protein food is consumed solely for the sake of its carbonaceous molecule, which may play some part in the organism that the ordinary non-nitrogenous foods cannot play; (2) that the excess of protein food is required for its stimulating effect upon metabolism. The former proposition has so far obtained no adequate support, and the latter is a double-edged weapon, for it may very properly be objected that all undue stimulation is unphysio-logical and deleterious to the best interests of the body.

Hence from the results of his experiment Chittenden concludes that the daily protein requirement of an adult receiving a sufficiency of non-nitrogenous food to supply the energy demands of his body is .85 gram per kilogram of body-weight, equal to an excretion of .12 grams of nitrogen per kilogram. A man weighing 70 kilograms, or 154 pounds, would therefore need 60 grams of protein food daily, equal to one half the Voit standard, much less than the Atwater standard, and infinitely below the ordinary consumption of protein food in Europe and America as indicated by the published dietary standards.