Needless to say, it is seldom that such methods of research are invoked to determine the amount of food required, but their description gives an opportunity for explaining many invaluable points connected with diet. It is much more usual to adopt the experimental or empirical method, where the actual food supply of healthy individuals is noted and the excretions from kidney, bowel, etc. fully analysed to discover whether the expenditure is properly balanced. An extension of this system in the form of deliberate feeding experiments upon selected individuals has now been much in vogue in various countries, and the observations in large measure corroborate the results obtained by calorimetry and other scientific methods. The fuel value of the food required varied from as little as 2000 calories for sedentary individuals to as much as 6000 calories for those engaged in laborious occupations.

This is, of course, much too wide a latitude to be of any real practical value to the individual who wants something more precise. The following figures have been supplied by Von Noorden of Vienna. He suggests that the maintenance diet for a man weighing 70 kilograms (i.e. 168 lbs.) should be

After long consideration I am satisfied that the average business man is amply provided for by 2700 calories of food per day.

How much Protein is Required?. - This is one of the most difficult and contentious problems in the whole range of dietetics. One school maintains that you require at least 125 grams, i.e. about 4 ounces, whilst another insists that not more than one half of this, or about 60 grams, is ever required by anyone. The explanation of this serious difference is simple enough, for it is found that nitrogen equilibrium may be maintained on very variable quantities of protein. From the remarks we have already made it will be apparent that the problem is complicated by the fact that proteins can be utilised in the body both as building material and fuel substance. We must therefore decide whether it is feasible, and if so healthy and legitimate, to reduce the supply of protein to the exact amount required for repair purposes, relying entirely on the carbohydrates and fats for providing heat and work, or use the protein for the double purpose. Upon our answer to this question will depend our position as supporters of those who like Chittenden advocate the minimum supply of protein, or those who like Voit adhere to the regulation standard. There is much to be said on both sides of the question.

Voit insists that a full supply of protein is essential to a full measure of health and strength, to maintain a powerful opposition to the incidence of disease, a vigorous digestion, and to impart such stimulation to the system as betokens the possession of vital energy.

Chittenden, on the other hand, argues that no protein can be stored in the tissues, that excess of protein propagates toxins which gain access to the circulation and poison the body, that energy is lost in excreting the surplus protein, that disease is eradicated and the body rendered much healthier on a low supply of protein.

The truth apparently lies midway between the views of the two protagonists, as a careful analysis of the average diet-list will determine, but I am personally convinced that the amount of protein necessary is certainly an individual question which is settled for each by a little experience and reflection. Any person who never takes less than 1 gram of protein per kilogram of his body weight, i.e. for a man weighing 10 stones about 2 ounces of protein, is not likely to go far wrong so long as he eats a sufficiency of carbohydrates and fat to supplement it. This is, however, a most important point, as within limits the greater the quantity of fat and carbohydrate supplied along with the protein the less is the latter used for supplying heat and work, and the more therefore is available for tissue-building purposes. This is what is meant when it is stated that fats and carbohydrates are "protein sparers," and the ideal condition would be to find the exact quantity which would allow the body to use all the nitrogen in protein for purposes of tissue repair.

On the above basis the full amount of protein requisite for a day's allowance would be equal to 60x4.1 = 246 calories, and would be found in 12 ounces of beef, 10 ounces of lamb, 8 ounces of mutton, 35 oysters, 12 ounces of salmon - none of which contain much in the way of fat and no carbohydrate at all; 10 ounces of almonds, 3 1/2 pints of milk, 6 ounces of pine kernels, 10 eggs, 8 ounces of cheese - all of which contain either carbohydrates or fats and some of them both.

On the other hand, those who accept the higher standard of 125 grams, over 4 ounces of protein, would require to eat 20 eggs, or about 5 platefuls of cooked meat (20 ounces), in order to assure their day's allowance of protein. Doubtless the man who takes from 80-90 grams, about 3 ounces of protein daily, will not sustain any damage thereby and is certain to be amply catered for.

The Requisite Quantity Of Fat And Carbohydrate

It may be inferred from what has been said that this will depend on the amount of protein consumed. If we allow 80 grams, or 328 calories, of protein and agree that 2700 calories are required daily, that would leave roughly 2370 calories to be supplied by non-nitrogenous food.

So far as the tissues are concerned it would not matter whether we decided to select these either from fat or carbohydrate, but there is a limit to the digestive capacity for the former and indeed for the latter. It is largely, however, a matter of temperament and nationality, the Esquimaux depending largely upon fat and the Hindoos on carbohydrate. There should be little difficulty in the digestion of 100 grams of fat per day, and that would be contained in 5 ounces of butter, and represent 930 calories, leaving 1470 to be provided by carbohydrate. About 14 ounces of sugar, or 370 calories, would fulfil the daily demands of the system for carbohydrate.

Needless to say, these proportions are not accepted by all. Dr. Kellogg of Battle Creek Sanitarium firmly believes in a low-protein fleshless diet constructed as nearly as possible of 10 per cent. protein, 30 per cent. fat, and 60 per cent. carbohydrate, whereas the diet we have been considering has close upon 14 per cent. of protein, more than 30 per cent. fat, and less than 60 per cent. carbohydrate.