An interesting New York Times article on bone density, or the loss of it, in competitive cyclists.  But it isn’t clear how much it applies to us long distance recreational riders.  It probably does say that drinking milk or other calcium rich beverages while on our brevets is probably a very good idea and suggests that we might be better off if we get some other form of exercise on a regular basis, be it weight lifting, running, hiking, etc, but probably not swimming.

Bruce

http://well.blogs.nytimes.com/2009/07/01/is-bicycling-bad-for-your-bones/?hp