Vitamin D – the sunshine vitamin known since ancient times is essential to good health from rickets avoidance to cancer prevention
Why did Persian warriors have softer skulls?
Since ancient times, man has been aware of the substance we now know as Vitamin D (aka Vitamin D3). The father of modern medicine, Hippocrates, used heliotherapy, or exposure to sunlight, to treat a condition called “phthisis,” which was most likely pulmonary tuberculosis or a similar progressive systemic disease.
The Greek historian Herodotus even observed that Persian warriors had much softer skulls than Egyptian warriors. He believed this was caused by the turbans worn by Persians, which could have attributed to a disease similar to rickets.
Rickets became rampant in the 17th century
The first scientific description of rickets was provided in the 17th century by both Dr. Daniel Whistler (1645) and Professor Francis Glisson (1650). By the late 1700s, it became rampant in Europe as people began to stay indoors and live in large, polluted cities, with reduced exposure to sunlight.
Beginning in the 1820s, it was noticed that city child were more likely to have rickets than rural children. In the 1890s, scientists began to search for specific foods that could prevent rickets. Such reasoning was rooted in the knowledge that two other diseases, scurvy, and beriberi, could be prevented by the addition of certain foods (such as citrus fruits, which contain Vitamin C, and whole grain rice, which contains Vitamin B1) to the diet.
Isolation of Vitamin D, Nobel Prize, the incidence of rickets and cancers
Half a century later, it was noted that children raised in sunny climates virtually never developed rickets. American researcher Dr. Elmer McCollum isolated Vitamin D, receiving the Nobel Prize. Other scientists later observed that people with skin cancer had lower prevalence of nonskin cancers and that lower overall mortality rates from all internal cancers combined existed in sunnier areas.
In 1913, McCollum and fellow researcher Ms. Marguerite Davis discovered a substance in cod liver oil which later was called “Vitamin A”. British doctor Edward Mellanby noticed dogs that were fed cod liver oil did not develop rickets and concluded Vitamin A, or a closely associated factor, could prevent the disease. In 1921, Dr. McCollum tested modified cod liver oil in which Vitamin A had been destroyed. The modified oil cured the sick dogs, so Dr. McCollum concluded the factor in cod liver oil which cured rickets was distinct from Vitamin A. He called it Vitamin D because it was the fourth vitamin to be named.
We, humans, do synthesize Vitamin D by exposure to sunlight (UV light)
It was not initially realized that, unlike other vitamins, Vitamin D can be synthesized by humans through exposure to UV light. By the 1920s, however, other researchers had stumbled onto the fact that exposure to sunlight was also completely effective in curing and preventing rickets.
Eventually, these two cures for rickets were merged in the demonstration that simply eating food that had been irradiated was sufficient. Therefore, irradiating certain foods became standard practice in the 1920s for preventing rickets in the general population. The chemical compound responsible for this success, Vitamin D, was identified in the 1930s, thanks to researchers studying the chemical structures of members of the cholesterol family.
Correlation between colorectal cancer, Vitamin D and lines of latitude
The study of Vitamin D progressed very little until 1970 when maps were created of cancer mortality rates. Through the study of these maps, Drs. Cedric and Frank Garland of Johns Hopkins University reported a strong latitudinal gradient for colon cancer mortality rates in 1980 and hypothesized that higher levels of Vitamin D compounds in the serum of people in the south were responsible and that calcium intake also would reduce incidence.
Dr. Edward Gorham and colleagues carried out several studies, including the first study that found an association of a serum Vitamin D compound with reduced cancer risk. Dr. William B. Grant then carried out numerous ecologic studies that extended the Vitamin D-cancer theory to other cancers.
Discovery of the metabolism of Vitamin D to the active hormone
In 1971-72 the further metabolism of Vitamin D to active forms was discovered. In the liver Vitamin D was found to be converted to calcidiol. Part of the calcidiol is then converted by the kidneys to calcitriol, the biologically active form of Vitamin D. Calcitriol circulates as a hormone in the blood, regulating the concentration of calcium and phosphate in the bloodstream and promoting the healthy growth and remodeling of bone. Both calcidiol and calcitriol were identified by a team led by Dr. Michael F. Holick of Boston University Medical Center.
Vitamin D3 is now available as a dietary supplement
Today, several companies produce large quantities of the primary form of Vitamin D, also known as Vitamin D3 or cholecalciferol. The process of the commercial manufacture of vitamin D3 mimics the manufacture of the cholecalciferol in animals. In general, cholesterol is purified from animal products (like lanolin from sheep wool) and used as starter material for purification and conversion into Vitamin D3 by irradiation.
Commercially manufactured Vitamin D3 is added to many foods, particularly milk products; it is also a key ingredient in dietary supplements and multivitamin supplements.