In the summer of 1974, brothers Frank and Cedric Garland had a heretical brainwave.
The young epidemiologists were watching a presentation on death rates from cancer county by county across the United States. As they sat in a lecture hall at Johns Hopkins University in Baltimore looking at the colour-coded cancer maps, they noticed a striking pattern, with the map for colon cancer the most pronounced.
Counties with high death rates were red; those with low rates were blue. Oddly, the nation was almost neatly divided in half, red in the north and blue in the south. Why, they wondered, was the risk of dying from cancer greater in bucolic Maine than in highly polluted Southern California?
The two had arrived at Johns Hopkins a few days earlier, having driven their Mustang from their hometown of San Diego. Frank was about to begin graduate studies and Cedric his first job as a professor. It was July, and the trip through the sunny South gave them an idea as they studied the cancer maps: Exposure to sunshine varies dramatically depending on the latitude. What if that's what was behind the varying cancer rates?
Their hypothesis, painstakingly developed and published six years later in the International Journal of Epidemiology, was that sunlight has a powerful anti-cancer effect through its role in producing vitamin D in bare skin. Those living at northern latitudes, they theorized, receive less sunlight and make less of the vitamin, which in turn increases their risk of dying from cancer.
Today, with vitamin D so much in the news, it's hard to believe that it took decades for the Garlands' hypothesis to gain traction in the mainstream medical community.
But the benefits of vitamin D are no longer restricted to cancer prevention: Studies have linked a shortage of the compound to such serious, chronic ailments as multiple sclerosis, diabetes, heart disease, influenza and schizophrenia.
Cedric Garland, now a professor of preventive medicine at the University of California, San Diego, is so convinced of this broad link that he says, "I think vitamin D is introducing a golden age in medicine."
And he's not alone. So compelling is the latest research that a number of credible medical researchers and public-health advocates, many of them in Canada, have started taking doses far above 200 to 600 international units - the daily intake recommended by Health Canada, depending on age with an upper limit of 2,000 IU.
Canada's leading vitamin D researcher, the University of Toronto's Reinhold Vieth, says he has been knocking back 8,000 units a day - four times the maximum - for years.
Should everyone be doing the same?
Dr. Vieth says he believes that what he's doing is completely safe - after all, his intake is similar to the amount of vitamin D a sunbathing Canadian might make naturally on a summer day.
And Robert Heaney, a medical researcher at Creighton University in Omaha, says his Canadian colleague is hardly alone in his super-sized approach. "All the vitamin D researchers, to a person, I've not found an exception, are convinced enough by the data to walk the walk," says Dr. Heaney, who last year helped to conduct a study, reported in the American Journal of Clinical Nutrition, that linked vitamin D supplements to an astonishing 60-per-cent decrease in cancer incidence among middle-aged and older women.
Cedric Garland argues that, rather than pollutants or some other cause, insufficient levels of vitamin D are at the root of the Western world's cancer epidemic. What's more, if more people took supplements, the population of northern regions would be a lot healthier all round.
"We will be preventing an extremely broad range of diseases in a single, inexpensive way with virtually no complications," he explains. "It will affect every branch of medicine and public health favourably."
TOO GOOD TO BE TRUE?
It seems almost inconceivable that geography could damn someone to a life-threatening illness - that the mere fact of living in a northern country such as Canada could be a health hazard.
The Garland brothers' hypothesis also defies the long-held conventional view that cancer is caused mainly by bad lifestyle habits, bad genes or carcinogens. Indeed, it suggests that some types of cancer could be better described as nutritional-deficiency diseases, much like scurvy or rickets.
Consequently, many experts have been skeptical, aware that much-touted nutrients in the past have often failed to live up to their initial hype.
"The problem with vitamins has been that generally the evidence, for whatever reason, doesn't pan out," cautions Len Lichtenfeld, deputy chief medical officer of the American Cancer Society.
Dr. Lichtenfeld says medical authorities have been burned so often over supplements that he would like to see a "substantial amount" of additional research before he is convinced that vitamin D is the real thing.
The idea that sunlight has beneficial health effects also flies in the face of advice to avoid sun exposure to reduce the risk of skin cancer.