You're listening to Outside In. I'm Nate Hedgy.

Let's go back to the year 1901.

The man, a young dentist named Frederick McKay.

He had just arrived in a small frontier town called Colorado Springs.

And as soon as he got there, he noticed something strange.

The townspeople, who became his dental patients, had dark brown spots all over their teeth.

We were talking the color of chocolate.

But interestingly, when he looked at them, he noticed that they didn't have cavities.

Brown teeth, few cavities.

That, by the way, is Renee Nahara.

He's an epidemiologist and director of public health at the College of Physicians of Philadelphia.

He says Frederick McKay noticed this was a regional thing.

In other towns, kids had teeth that were normal for the time with plenty of cavities,

but they were nice and white teeth.

The condition was nicknamed Colorado Brownstain.

Locals blamed the phenomenon on a number of things.

Eating too much pork, drinking funky milk.

Or maybe there was something in the water.

That last theory had legs. There was this other town in Idaho that also had Colorado Brownstein. But when they switched to a different water source, it went away. Then there was

this mining town in Arkansas.

They also had cases of Colorado Brownstein,

yet a town five miles away didn't.

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