I'll admit to being a full-fledged running geek. I would have loved to do a study like the one the Danes did in this documentary. I've heard many theories over the years about why the Kenyans are superior distance runners, but I had never heard about this particular theory.
I won't spoil it, in case you're interested in watching this (and if you do, you're a fellow running geek, for sure!), but I will say that I was surprised by their conclusion. This was filmed in 2001.