Vitamin imbalance in metabolic disease.

A T THE TIME when an increasing number of clinical conditions were recognized as deficiencies of one or another chemical substance, such so-called vitamins were measured by their effect as supplement to a basal diet upon the growth and health of some species of laboratory animals. Vitamins are organic substances of natural origin, required in minute quantities, and their effects are not based on their caloric value, but exclusively on their catalytic nature. Elucidation of their structure and biosynthesis are exciting chapters of organic chemistry, and their identification with the prosthetic groups of vital enzymes is a signal contribution to biochemistry. The recognition of their structure permits the determination of vitamins by the tools of analytical chemistry, but while such methods are widely used in industrial production, the minute quantities in body fluids and tissues limit the purely chemical approach to a few members of this group present in relatively high concentration; e.g., vitamin C. Microchemical methods are in use for the determination of thiamine, riboflavin, and some of the fat-soluble vitamins, on the basis of the most sensitive colorimetric and, in particular, fluorometric technics. Vitamin D, on the other hand, is determined by animal assay. Vitamins, especially the water-soluble ones, provide the co-enzymes for the most fundamental cellular reactions. Thus, their presence is