Researchers suspect vitamin D plays such a crucial role in diseases as unrelated as cancer and osteoporosis because the chemical originated in the early days of animal evolution as a way for cells to signal that they were being exposed to daylight.
Even though living things have evolved since then, almost all cells, even those deep in our bodies, have kept this primitive light-signalling system.
In the body, vitamin D is converted into a steroid hormone, and genes responding to it play a crucial role in fixing damaged cells and maintaining good cell health. "There is no better anti-cancer agent than activated vitamin D. I mean, it does everything you'd want," said Dr. Cannell of the Vitamin D Council.
Some may view the sunshine-vitamin story as too good to be true, particularly given that the number of previous claims of vitamin cure-alls that subsequently flopped. "The floor of modern medicine is littered with the claims of vitamins that didn't turn out," Dr. Cannell allowed.
But the big difference is that vitamin D, unlike other vitamins, is turned into a hormone, making it far more biologically active. As well, it is "operating independently in hundreds of tissues in your body," Dr. Cannell said.
Referring to Linus Pauling, the famous U.S. advocate of vitamin C use as a cure for many illnesses, he said: "Basically, Linus Pauling was right, but he was off by one letter."