Yes, you are doing harm if you discourage older people from getting the nutrients they need to preserve bone density. Adequate vitamin D levels are necessary for the bones to absorb calcium and thus stay strong and free of fractures. Fractures are a major risk for older cyclists because many have low bone density. In the past 2 years in my group of maybe 30 older cyclists we have had 8 crashes which resulted in serious fractures. This is serious business. See: http://www.bikeforums.net/training-n...n-improve.html