When humans are exposed to sunlight, their skin produces vitamin D, a fat-soluble vitamin that offers many health benefits. These benefits include helping maintain a healthy immune system, and the growth and development of bones and teeth.
The following excerpt from the book, Solar Power for Optimal Health, describes the importance of vitamin D, as well as how it was first discovered.
Sunshine is a marvelous health-giving and healing power in the world. While sunshine is death to disease-producing agencies, it is life and health to all natural forms of life.
Sit in the sun, recline in the sun, walk on the sunny side of the street, avoid parasols, and ever recognize the sun as a friend and not an enemy, a promoter of health, and a destroyer of disease.
To understand the history and function of vitamin D (whose production is stimulated by sunlight), you should know the differences among the different types of ultraviolet light:
1. Ultraviolet light (UV) is a light that is invisible because its wavelength is shorter than the violet part of the sunlight spectrum. UV is available year round in the tropics and during part of the year farther north and south.
UV is also produced by sunlamps. There are three main varieties of UV: UVA, UVB and UVC. UV wavelengths are measured in nanometers (one billionth of a meter).
a. UVA has a wavelength of 320-400 nanometers and when contacting the skin can penetrate beyond the outer layer (epidermis) into a layer called the dermis. UVA does not stimulate vitamin D production.
b. UVB light has a wavelength of 280-320 nanometers and penetrates only the epidermis when it contacts the skin. UVB stimulates the skin, which produces vitamin D.
c. UVC light has a wavelength of 200-280 nanometers and is filtered out by the Earth’s outer atmosphere.
A brief history of life-sustaining vitamin D, the sunshine vitamin
As early as the mid-seventeenth century, two scientists working independently of each other identified the disease called rickets and observed that it occurred among children who were seldom exposed to sunlight.
This illness was characterized by defective bone growth and horribly deformed bodies. By the twentieth century it was well established that rickets had something to do with lack of sunlight.
It was not until 1919-1921, however, that Sir Edward Mellanby’s studies on dogs helped define the substance whose absence caused rickets. His dogs were fed only oatmeal, and they were raised without any exposure to sunlight, which caused them to develop the disease.
By observing the effects of different diets, Mellanby determined that if they lacked a particular substance, rickets developed.
The link between sunlight deficiency and rickets
He found that the substance was contained in cod liver oil, which he stated was an effective anti-rickets agent; the dogs were cured by adding cod liver oil to their diets.
Shortly afterward, Dr. E.V. McCollum and his team performed experiments on the substance they thought was a “fat- soluble vitamin” and differentiated it from vitamin A.
They had found the substance that “promotes calcium deposition” and named it “vitamin D,” which was a mistake since it is not a vitamin, but the name stuck.
A year later, a Dr H. Goldblatt and his team exposed cholesterol in skin to ultraviolet light and produced the exact substance that had been labeled a fat soluble vitamin.
Nearly simultaneously, Dr. A. Hess performed an experiment in which he exposed animal skin to ultraviolet (UV) light and then fed it to sunlight-deprived rats. The rats were completely protected from rickets.
Another researcher, Dr H. Steenbock, discovered that irradiating various foods with UV from sunlamps caused those foods to have anti-rickets properties.
In the 1930’s, the chemical structure of vitamin D was established by German scientists, and they proved that the substance in cod liver oil was vitamin D.”
Vitamin D was then established as a prohormone, a substance that is later converted into an active hormone.
Though the interest in vitamin D’s power was originally limited to the prevention and treatment of rickets, it would later be found that this substance had myriad other benefits.