In 1980, two epidemiologists brothers noticed a stunning pattern.

The farther north Americans lived, the more likely they were to be diagnosed with colon cancer.

Scientists later found that people with low levels of vitamin D, which our skin can make when

it's exposed to sunlight, were at greater risk of autoimmune problems, cardiovascular disease,

breast cancer, depression, and dementia. That research made vitamin D a superstar nutrient, given how simple and cheap it is to

use supplements to boost our levels, except using vitamin D to prevent or treat those same diseases

has turned out to be pretty much useless. And yet, those latitude gradients of geographic

disease distribution persist. From KERA in Dallas, this is

think. I'm Chris Boyd. So if it wasn't vitamin D keeping people from getting sick, what was it

that protected populations of people exposed to larger amounts of sunlight? Here's a radical thought.

Some scientists now believe sunlight itself might

confer health benefits. Rowan Jacobson is a science journalist who wrote about the latest research

in a scientific American article titled, Can Sunlight Cure Disease? Rowan, welcome to think.

Thanks, Chris. Great to be here. So let's start with this strange pattern of certain

diseases being more common, the farther people live from the equator. How long have doctors

observed something like that? Yeah, you know, it actually goes back more than 100 years.

The first like hints that doctors would see that people living at high latitudes

had higher rates of these diseases.

And they didn't know what was responsible for a while.

And they speculated everything.

But then, you know, it became pretty clear that it had something to do with sunlight.

But as you just said in that intro, once we'd figured out that vitamin D was an important factor

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