It has long been known that certain foods provide protection against a range of serious illnesses. For example, the ancient Egyptians discovered that night blindness could be prevented by eating liver. Similarly, in the 18th century, Scottish doctor, James Lind, discovered that citrus fruits could counteract the effects of scurvy. At the time, of course, it wasn’t known what particular components of those foods (vitamins A and C respectively) were responsible for the observable health benefits.
In 1881, Russian surgeon Nikolai Lunin started putting the pieces together by proposing the theory that foods must contain small traces of nutrients that are essential for good health. He came to this realization after conducting an experiment in which he fed one lot of mice on whole milk and another lot on the main ingredients of milk (proteins, fats, carbohydrates, and salts). The first lot thrived and the second lot died. Unfortunately his theory was rejected because others were unable to obtain similar results. This was largely because they used sugar derived from milk (which contained vitamin B) whereas Lunin used table sugar.
Further discoveries were made in the early 1900s of links between diet and disease. For example, William Fletcher found that eating whole rice, as opposed to white rice, helped avoid the disease beriberi. These discoveries led English biologist F. Gowland Hopkins to reiterate Lunin’s theory, saying that unknown “accessory substances” existed in food that were essential for both growth and good health.
In 1912, Polish biochemist Casimir Funk discovered what the active ingredient was that gave brown rice its bioactivity. It turned out to be a complex of compounds known chemically as amines, which he named vital amines or vitamins. Over the next few years, researchers found other vital accessory factors in different foods. For example vitamin A was discovered in butter and fish oil, and vitamin C was discovered in citrus fruit. They were assigned various letters of the alphabet because their actual chemical makeup was unknown at the time. The B group of nutrients was originally thought to be a single substance, hence the later need for subdivision. In 1920, it was discovered that vitamin C was not an amine, so it was suggested that the trailing “e” be dropped from future usage for all these essential nutrients.
Throughout the 20th century, this new knowledge of vitamins was put to good use. Deficiency diseases like rickets (vitamin D), scurvy (vitamin C), and beriberi (vitamin B1) were now understood and could be easily treated by supplementing the diet with the appropriate vitamin. The previously incurable pernicious anemia could now be treated with raw beef liver, which was found to be abundant in vitamin B12. As advances were made in chemistry, it became possible to cheaply manufacture synthetic versions of vitamins, thus ensuring that the benefits of this medical breakthrough were widely available.