Aaron Spitz, MD, is the director of male reproductive and sexual medicine at Orange County Urology Associates. He's served as president of the California Urological Association, was the lead urology delegate to the American Medical Association, and has been an assistant clinical professor at UC Irvine's Department of Urology for the past decade and a half.

Impressive, no doubt. But cinematically compelling? You might not think...

In one of the final parts of the documentary filmed before submitting it to Sundance, Dr Spitz performs an experiment with three male college athletes. They eat a meat-filled burrito for dinner one day, and a plant-based version of the same burrito the next. Both nights, the guys are hooked up to devices that measure the size and duration of their erections.