Original of this article was published on ZRT Laboratory Blog. Last reviewed: May 2026.
The Search for Missing Nutrients
Scientists in the early 20th century were swiftly realising that the nutritional requirements to “support life, growth and reproduction” in both animals and humans were more than simply proteins, carbohydrates, fats and minerals. In 1912, Casimir Funk isolated a substance found in the hulls of rice that cured beriberi, a nutritional disease linked to thiamine (B1) deficiency. From this revelation, he theorised that other diet-related ailments such as pellagra, scurvy and rickets could also be a consequence of deficiencies of yet unidentified substances. He called these substances “vital amines” or “vitamines” — a term that became a major focus of nutritional research for the next 30 years, yielding discovery after discovery of essential nutrients.
How Vitamin D Was Discovered
In 1917, building on previous research, Elmer V. McCollum began experiments with rats fed modified diets resulting in rickets — a malady prevalent in Europe, particularly in Scotland, and the northern US. McCollum fed rats a diet with an imbalanced ratio of calcium to phosphorus, which created rickets. He knew that cod liver oil had been shown to prevent rickets, and having already isolated vitamin A in cod liver oil, he speculated this nutrient was the factor responsible. However, after using oxygen to destroy the vitamin A in the cod liver oil, it still retained the ability to cure rickets — meaning another factor was responsible.
Exposing an infant to sunlight was a traditional folk remedy in Europe for the treatment of rickets, and experiments using ultraviolet (UV) lamp exposure were also known to be effective. A breakthrough occurred when it was found that not only was the irradiation of rachitic rats curative, but irradiation of the imbalanced mineral rations that caused rickets was also curative. This contradiction led to many researchers trying to isolate the factor triggered by UV waves — a process that was generating vitamin D2 (ergocalciferol). Rapid progress led to separation of a lipid, then to a sterol fraction, and finally in 1931 vitamin D was crystallised.
What We Know About Vitamin D Today
Today we know that vitamin D3 (cholecalciferol) is synthesised in our skin through exposure to sunlight. We also know that vitamin D has a complex regulatory effect upon calcium in our bodies and in the mineralisation of our bones. But that’s only skimming the surface of this vitamin’s function. Further exploration has generated knowledge of the effects of vitamin D on many disease processes including breast, colon and prostate cancer, heart disease, both type 1 and type 2 diabetes, and depression, to name a few.
Our Vitamin D Test (Vitamin D2, D3 and D Total) uses a simple at-home dried blood spot collection to accurately measure your total vitamin D status — distinguishing between D2 and D3 to give you and your practitioner the most complete picture of your vitamin D sufficiency.
For women who want to assess vitamin D alongside a full hormone and wellness panel, our Advanced Female Wellness Test includes vitamin D alongside thyroid, sex hormones and other key markers — with a specialist doctor report included. For men, our Advanced Male Wellness Test provides the same comprehensive approach, covering vitamin D, testosterone, thyroid and cardiovascular markers in a single at-home test.
A Century of Discovery — Still Evolving
The winding road in the identification of vitamin D, as well as each individual vitamin, is a comparatively recent phenomenon in nutritional history. Yet one hundred years later, our understanding of vitamin D’s wider role is still embryonic. New associations to health are in the news almost daily. But thanks to pioneers like Casimir Funk, E.V. McCollum and many others, nutritional research and its importance to overall health continues to evolve.
Original of this article was published on ZRT Laboratory Blog.