i found this yesterday... but glucosamine can hurt pancreatic cells! Causes problems for diabetics (basically messes up your pancreas) and can cause asthma problems.
http://www.ncbi.nlm.nih.gov/pubmed/20110682
http://www.sciencedaily.com/releases/2010/10/101027111349.htm
http://www.ncbi.nlm.nih.gov/pubmed/11893929
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3042150/
http://www.ncbi.nlm.nih.gov/pubmed/1231993