The Vitamine Manual | Page 4

had already learned to use in measuring coal. For convenience the physicists devised a heat measure unit for this purpose and naturally called it by a word that means heat, namely, "calorie." Using this unit and applying the isodynamic law it was merely necessary to determine two things; first, how many calories a man produces in any given kind of work, second how many calories a given weight of each kind of food will yield, and then give the man as many calories of food as he needs to meet his requirements when engaged in a given kind of labor. The measurement and tabulation of food values in terms of calories and the investigation of the calorie needs of men and women in various occupations has been one of the great contributions of the past twenty years of nutritional study and to the progress made we owe our power to produce proper rations for every type of worker. Army rations for example are built up of foods that will yield enough calories to supply the needs of a soldier and during the recent war extended studies conducted in training camps all over the United States have shown that when the soldier eats all he wants he will consume on the average about 3600 calories per day. In France the American soldier's ration was big enough to yield him 4200 calories per day if he ate his entire daily allowance.
But calories are not the only necessities. A pound of pure fat will yield all the calories a soldier needs in a day but his language and morals wouldn't stand the strain of such a diet. Neither would his health, for not only does his body demand fuel but also that it be of a special kind. While there are many kinds of foodstuffs, chemical analysis shows that they are mainly combinations of pure compounds of relatively few varieties. The chemists call these proteins, fats, carbohydrates, and salts. Meats, eggs, the curd of milk, etc., are the principal sources of protein. Sugars and starches are grouped together under the name of carbohydrate. By salts is meant mineral matters such as common salt, iron and phosphorus compounds, etc. In selecting foods it was found that the body required that the proportions of these four substances be kept within definite limits or there was trouble. We know now that a man can get along nicely if he eats 50 grams of protein per day and makes up the rest of his calories in carbohydrates and fats, provided that to this is added certain requirements in salts and water.
It is also obvious that the foods given must be digestible and palatable.
We had reached this status some time before 1911. But, a short time before this, there had arisen a controversy as to the relative value of different types of proteins. The animal- vs. vegetable-protein controversy was one of the side shows of this affair. This controversy had led to a careful study of the different kinds of proteins that are found in foodstuffs. Through a brilliant series of chemical investigations for whose description we haven't time or space here, chemists had shown that every protein was built up of a collection of acids which were different in structure and properties, that there were some seventeen of these in all and that any given protein might have present all seventeen or be lacking in one or more and that the proportions present varied for every type of protein. It was then obvious that proteins could not be considered as identities. More than that, it was the necessary task of the food expert to separate all proteins into their acids or building stones and not only show what was present and how much but determine the r?le each played in the body. To this task many set their faces and hands.
From the results there has accrued much progress in the evaluation of proteins but an unexpected development was the part played by these investigations in the story of the vitamines.
About 1909-1910 Professors Osborne and Mendel under a grant from the Carnegie Institution began a detailed investigation into the value of purified proteins from various sources. In their experiments they used the white rat as the experimental animal and proceeded to feed these animals a mixture consisting of a single purified protein supplemented with the proper proportions of fat carbohydrate, and mineral salts. Since the food furnished was composed of pure nutrients and always in excess of the appetite of the rat the necessary number of calories was also present. These researches were published as a bulletin (No. 156) by the Carnegie Institution in 1911, the same year that Funk announced his Vitamine discoveries. It was timely in this respect for one of Osborne and Mendel's discoveries was