When I ran cross-country in high school and college (7 and 6 years ago, respectively), I experienced 2 metatarsal stress fractures
(one in each foot, subsequent years) and
had low bone
density (osteopenia) as a result of an eating disorder. I had been on fosamax for awhile, take calcium, and my weight is back to normal, so supposedly my bone density is fine now. I was also not running like I had in the past, but took regular walks and we blamed the pain on worn out tennis shoes.