The Greek historian Herodotus (485-426 BC) observed that Persian warriors had softer skulls than their Egyptian counterparts, attributing this to the turbans worn by the Persians, which limited their exposure to sunlight. Hippocrates also described a disease resembling rickets as early as 130 AD, indicating an ancient awareness of conditions later understood to be linked to vitamin D deficiency.
In the 17th century, the first scientific descriptions of rickets were provided by Dr. Daniel Whistler in 1645 and Professor Francis Glisson in 1650. These pioneering observations laid the groundwork for understanding this bone-deforming disease. By the late 18th century, cod liver oil was identified as a treatment for chronic rheumatism, and its efficacy in treating rickets was soon discovered.
Rickets became a prominent topic of medical inquiry in the 18th and 19th centuries. Chroniclers of the era noted its widespread occurrence, particularly among children in industrialized cities with limited sunlight exposure. It was recognized that a lack of a vital nutrient, later identified as vitamin D, was the cause.
From the 1820s, studies demonstrated that cod liver oil could cure rickets in afflicted children, establishing a direct link between the nutrient found in the oil and the prevention of the disease. This period marked significant progress in nutritional science, with the early 20th century witnessing major breakthroughs. Between 1910 and 1930, nutrition evolved into an experimental science, leading to the identification and appreciation of vitamins as essential dietary components.
A pivotal moment came in 1919/20 when Sir Edward Mellanby, conducting experiments with dogs raised indoors, established that rickets was caused by a deficiency of a dietary component. His work confirmed the crucial role of what he called a "fat-soluble vitamin," later known as vitamin D, in preventing the disease.
Shortly after, researchers E.V. McCollum and McCallum induced rickets in chickens through an incomplete diet and found that the disease could be cured with cod liver oil. This reinforced the idea that a specific vitamin in the oil was responsible for the therapeutic effect.
In 1923, Goldblatt and Soames identified that when a precursor of vitamin D in the skin (7-dehydrocholesterol) was irradiated with sunlight or ultraviolet light, it produced a substance equivalent to the fat-soluble vitamin. This discovery underscored the link between sunlight exposure and vitamin D synthesis in the skin.
Further advancements in 1924 by Huldschinsky, Hess, and Steenbock revealed that irradiating certain foods with sunlight or ultraviolet light endowed them with antirachitic properties, leading to the identification of provitamin D. These findings consolidated the understanding that sunlight plays a critical role in vitamin D activation.
The 1930s saw significant progress in the chemical characterization of vitamins D2 and D3. Professor A. Windaus and his team at the University of Gottingen determined the first analogues of these vitamins, establishing a foundation for their synthesis. In 1932, vitamin D2 was chemically characterized as a product of ultraviolet irradiation of ergosterol, and by 1936, vitamin D3 was identified as resulting from the ultraviolet irradiation of 7-dehydrocholesterol.
By the 1970s, it was learned that vitamin D itself was not the biologically active principle responsible for healing bone disease but rather its metabolites. This discovery led to a deeper understanding of the vitamin D endocrine system and its extensive role in bone health and calcium homeostasis.
Today, the significance of vitamin D extends beyond bone health, with research indicating its involvement in immune function, cardiovascular health, and even cancer prevention. The journey from Hippocrates' heliotherapy to the modern understanding of vitamin D underscores the profound impact of scientific discovery on public health and disease prevention.
The History and Importance of Vitamin D in Health
