VITAMINES. 1915.

Abstract

In the days when physiology was just beginning to be recognised as a distinct science, the articles of our food were regarded as made up of three classes of materials--fats, carbohydrates, and proteins--and it was thought that if these materials were present in the diet in sufficient quantity, the maintenance of healthy life was ensured. With the lapse of time the importance of quality as well as quantity has gradually dawned upon us, and we now know that food must contain not only proteins, carbohydrates, and fats, but certain definite kinds of these principles, together with small quantities of mineral salts, if it is to be considered satisfactory from the maintenance-of-health point of view. If the protein element, for instance, is deficient in certain amino-acids, especially in aromatic amino-acids, such as tyrosine and tryptophane, no superabundance of other amino-acid constituents will compensate for the deficiency, and the food is unable to maintain the integrity of the living tissues. The essential factors of a complete diet are therefore more numerous than was formerly suspected, and the recognition of the limitation of the synthetic powers of the living organism has suggested the possibility that other substances may be present in the food - occurring, it may be, in only small quantities --which are nevertheless absolutely indispensable, whose withdrawal from the diet would be attended with eventually fatal results. We know that there are certain mysterious substances in the body--the so-called internal secretions, hormones, enzymes, and so forth - of which very small traces bring about changes of immense importance to the living organism. These substances are being constantly destroyed and renewed, and the peculiarity of their structure suggests that their elaboration is dependent upon the presence in the food of materials essentially different from the common proteins, carbohydrates, and fats. If these essential materials are persistently absent from the diet, the normal metabolic processes are likely to become disturbed and deranged, culminating in pathological changes of a more or less pernicious character. The justification of this hypothesis is to be found in the remarkable light which it throws upon our knowledge of a number of diseases which appear to be caused by a too rigid restriction of diet. Such diseases have been grouped together under the term Deficiency Diseases, and include beri-beri, pellagra, scurvy, rickets, and other less well-defined conditions. A certain amount of evidence has been accumulated to show that, in each case, the condition is attributable to the absence from the diet of an essential material, termed by Casimir Funk a vitamine, which is more or less specific in its action in preventing the onset of the disease. …