John Harvey Kellogg Believed Light Could Cure Diabetes

And a whole lot of other diseases

John Harvey Kellogg may be most famous for creating breakfast cereal—for which his more commercially minded brother actually deserves a lot of the credit—but his sanitarium was full of inventions that promised health and wellness. For instance, he was, the New York Times wrote in 1943, "inventor of the electric light bath."
Kellogg started running the Seventh Day Adventists' health-reform institute—what would become the Battle Creek Sanitarium—in 1876, at a time when scientists in the U.S. and Europe were investigating the effects of light on plants and animals. One of Kellogg's contemporaries, Niels Finsen, would win a Nobel Prize for his work on phototherapy, which, he showed, could be used to treat certain diseases (most notably, lupus).
Modern medicine, too, has found that light therapy can be useful in treating certain conditions, including seasonal affective disorder. But Kellogg believed that light could cure a whole range of ailments. Bathing in light, he wrote in 1910, had cured England's King Edward of gout. It could help typhoid patients, people who had survived scarlet fever, and diabetics. Light was a treatment for obesity, scurvy, chronic gastritis, hyperpepsia, and constipation, according to Kellogg. He build the first incandescent light bath in 1891 and used light therapy to treat patients for years.
Even when the light therapy didn't cure disease, there was some reason to use it. Kellogg wrote:

"The electric-light bath prolonged to the extent of producing vigorous perspiration should be employed two or three times a week … Tanning the whole surface of the body means of the arc light will be an excellent means of improving the patient's general vital condition."

Perhaps Kellogg should get credit not just for creating breakfast cereal but another now-discredited modern marvel: the tanning bed.