If you are allergic to shell fish DO NOT take anything (even calcium supplements) that are made from oyster shells, mussel shells, etc. The iodine is still present.
Everybody knows it is tougher to get into veterinary school than people medical school--especially physicians. Then again, there is something about the FDA and trial attorneys breathing down physicians' necks.
I like hearing stories of good medicine that began with animals and have great respect for vets. My Keeshond is still tap-dancing at 13 with nary a creak. She gets some, but not much, glucosamine in her Nutro crunchies. If she ever needs more, I'll try green-lipped mussels as a source. I have a cheap online source for such things, http://www.beyond-a-century.com
I learned to trust vets 234987 years ago when I took my dog in with a terrible triangular tear in his cornea inflicted by a cat. While the vet removed the afflicted triangle, I read a vet magazine in the waiting room, which praised Vitamin E for healing wounds. Vet said "come back in a week for further treatment, but the dog will always have an opacity in that eye." So I took him home, kept flooding that eye and his food with E I squeezed from capsules, and voila! The next week there was no trace of opacity or any damage to the eye.
A couple of years later, a cat I loved got lost and into caustic substances. When found, the vet said, "Oh oh, this is death." Cat had gangrenous tongue, paws, and ears and who knows what damage inside from trying to lick the stuff off. I left him at the vet's for two weeks, then prepared meals for him including raw liver ground up with copious quantites of E and other nutrients. He would not eat the vet's food, but lapped up the stuff delivered daily from home. He recovered, minus the raspies on his tongue and literally regrew part of his ears. Went on to live 19 years!
So my first line of defense -- and offence -- against disease has always been extreme nutrition. Works for me!