I came across an interesting article this morning about ultramarathoner Scott Jurek, who also happens to be vegan. The article details the extreme amount of (healthy) food he consumes daily to support his 140-mile a week schedule.
I'm especially impressed because I actually stopped being a vegetarian when I started running more regularly. I was up to maybe 15 miles a week (not much, I know), and I just couldn't eat enough. I must admit that I didn't do a very good job of varying my protein sources, and I could have done much better research on how to support my athletic efforts. But the bottom line for me was that, at 110 pounds, I was nearly anorexic from not consuming enough calories to support my running. So I started eating meat.
Four years later, I don't regret this decision. I do enjoy meat. But I know it isn't good for me, and I eat vegetarian or vegan for lunch (and breakfast) most days. I do feel a twinge of regret for giving up so easily on my vegetarian lifestyle, and admire people who can be great athletes and great eaters, making a healthy vegan (or vegetarian) diet for themselves that supports their running.