The history of VITAMINS (pt. 2)

The term "vitamin" was coined by Casimir Funk in 1912 when he isolated the anti-beriberi factor. It was a fancy name at the time and has endured, despite the realization that not all essential substances are amines (organic forms of nitrogen). Funk was not the sole researcher investigating these unknown substances we now know as vitamins. The early 1900s saw the expansion of research in animals, initially conducted by Eijkman and later by Grijns and Pekelharing, which laid the foundation for further exploration. 

In England, between 1906 and 1912, Hopkins from Cambridge conducted experiments on rats and discovered that a diet consisting solely of pure protein, fat, and carbohydrates made the rats sick and resulted in their death. However, adding less than one-third of a teaspoon of milk per day to the purified diet proved to be life-saving for the rats, highlighting the presence of organic substances in milk. 

In 1911, independently of the European studies, Hart and his colleagues at the University of Wisconsin made similar observations regarding unknown substances in corn that were essential for cattle. In 1913, McCollum and Davis from Wisconsin provided evidence of an essential dietary factor in butter and egg yolk. They found that these substances were distinct from each other. 

In 1916, McCollum and Kennedy proposed the terms "fat-soluble A" and "water-soluble B" to differentiate the essential components in butterfat and milk whey. They discovered that one of these substances was soluble in water while the other was insoluble in water but soluble in fats. This led to the realization that there were multiple "accessory food substances" present in natural foods. 

In 1920, Drummond suggested that the different vitamins be referred to as vitamin A, B, C, and so on, combining McCollum's nomenclature with Funk's proposal. These naming conventions were quickly adopted.

During the 1920s and early 1930s, extensive research revealed that water-soluble "vitamin B" was actually a mixture of several unrelated vitamins. This led to the term "vitamin B complex," which is still used today to collectively describe the water-soluble vitamins other than vitamin C. The eight B complex vitamins share common features, including water solubility, the presence of nitrogen in their chemical structure, and significant amounts in the liver, the body's primary metabolic organ.

Due to limited knowledge about their chemistry, naming the individual vitamins initially posed challenges. As the vitamins were differentiated, they were designated using letters of the alphabet, typically in the order of their discovery. The fraction initially known as vitamin B was further subdivided into various chemical substances referred to as vitamin B1, B2, and so on, or by their chemical names. As the chemical identities of the different vitamins were established, the chemical names gradually replaced the earlier designations for specific compounds with vitamin activity. 

However, the letter system continues to be used when referring to groups of closely related substances that exhibit common vitamin activity. For instance, one refers to the "vitamin A activity" of several chemically related compounds. Most individual vitamins exist in nature in multiple chemical forms known as vitamers.