I have a friend who is generally averse to taking medication, for fear of side effects. Recently, however, he began taking a glucosamine supplement. He's had knee problems for quite awhile, which I think is his motivation behind doing so.
What is glucosamine and what does it do? Do any of you take it? Are there any possible harms, or more natural ways to help the knees/joints? (He runs several miles a week in spite of the pain, because he thinks it's good for his overall health). Thanks!