In addition to figuring out how to avoid injury, another thing that has helped me run so much has been changing my diet. About a year and a half ago, my wife convinced me to go gluten-free. I know, I know, the whole gluten-free thing is annoying, but just hear me out. Before I stopped eating wheat, one of the reasons I never even entered a 5k was that I was worried about my stomach. Before going gluten-free, my GI tract bothered me just running around the neighborhood sometimes, so I thought I’d never be able to run anything like a marathon.
Here’s a very good article supporting making this change in your diet. It’s a little long, but I’m sure people can manage to read it all: