But there are other differences between food and common fuel which are worthy of mention. The water and the salts are essential to meet the body's needs, especially the various mineral elements, lime, soda, potash and iron. All these we must have--lime for the bones and nerves, soda and potash to neutralize the harmful acid products of combustion processes, and iron for the blood.
All these are found in normal foodstuffs, but in greatly varying proportions, so that a pretty large variety of foods must be eaten to make sure that each of the different food principles required for perfect nutrition are supplied in ample quantity.
In recent years science has discovered another and most surprising property of food in which it transcends all other fuel substances as a diamond from the Transvaal outshines a lump of coal. Natural food contains vitamines. It has long been known that an exclusive rice diet sometimes causes beri-beri, a form of general neuritis, and that a diet of dry cereals and preserved food in time gives rise to scurvy, but the reason was a profound mystery. In very recent years it has been learned that the real cause of beri-beri and scurvy is the lack of vitamines which are associated with the bran of cereals and so are removed in the process of polishing rice and in the bolting of wheat and other grains.
Vitamines do not enter into the composition of the body as do other food principles, but they are somehow necessary to activate or render active the various subtle elements which are essential to good nutrition.
There are several kinds of vitamines. Some are associated with the bran of cereals, other with the juices of fruits. Some are easily destroyed by heat, while others survive a boiling temperature. The discovery of vitamines must stand as one of the most masterly achievements of modern science, even outshining in brilliancy the discovery of radium. It was only by the most persevering efforts and the application of all the refinements of modern chemical technic that the chemist, Funk, was able to capture and identify this most subtle but marvelously potent element of the food. This discovery has cleared up a long category of medical mysteries. We now know not only the cause of beri-beri and scurvy and the simple method of cure by supplying vitamine-containing foods, but within a very short time it has been shown that rickets and pellagra are likewise deficiency diseases, probably due to lack of vitamines, and in a recent discussion before the New York Academy of Medicine by Funk, Holt, Jacobi and others, it was maintained that vast multitudes of people are suffering from disorders of nutrition due to the same cause.