A New York pediatrician, Alfred Fabian Hess, observed that rickets was prevalent in immigrant (Italian) and African-American children and employed both sunlight and quartz crystal mercury-vapor lamps to prevent and heal rickets. Rickets could be prevented by UVB wavelength rays (289 and 302 nm), but not by UVA wavelengths, above 320 nm.
He was aware that rickets was most prevalent among his patients at the end of March 1922, when it was present in nearly 50% of the breastfed infants despite adequate maternal nutrition. Hess noted that “breastmilk, although valuable, is provided with but a scant factor of safety against rickets, and . . . additional protective influence is needed—namely, light.” As Sniadecki had done 100 years earlier, Hess identified lack of sunlight as the dominant etiologic agent in the rickets epidemic observed in temperate climates since the time of Glisson.
Hess and several other investigators were able to establish that mere exposure to sunlight could cure rickets. Hess and Mildred Weinstock confirmed the dictum that "light equals vitamin D". They excised a small portion of skin, irradiated it with ultraviolet light, and then fed it to groups of rachitic rats.
The skin that had been irradiated provided an absolute protection against rickets, whereas the unirradiated skin provided no protection whatsoever; clearly, these animals were able to produce adequate quantities of "the fat-soluble vitamin", suggesting that it was not an essential dietary trace constituent.
In 1922 Hess and L. F. Unger of Columbia University showed that by simply exposing rachitic children to sunlight, they were able to cure them of the disease.
Alfred Fabian Hess and rickets
