A recent study from the Inova Schar Cancer Institute has raised concerns by suggesting that extreme endurance running—such as marathons and ultramarathons—may increase the risk of precancerous colon growths in younger adults. While this study doesn’t prove that marathon running causes colon cancer, it does highlight a possible link that even very fit people should be mindful of regarding their colon health. Why might marathon running increase the risk? ““This is the first prospective study exploring whether exercise-induced intestinal stress from long-distance running might raise cancer risk. While not proving cause, results suggest intense endurance exercise could increase colorectal cancer risk and warrant further research.