First of all I love Dr. Mercola products so I was eager to try this one for our pups. We have a 13yo poodle mix with arthritis and a collapsing trachea so he is the one who will benefit most from this--at least, that's the idea. I sprinkle this on his food and after studying it for a bit, he agrees to eat it. There have been no negative side effects such as stomach upset. I haven't been administering this to him long easy to honestly say "I see a difference" but I do believe in the long term effectiveness of products like these, and I DO trust this particular brand. I am hopeful that with time, this product will make a difference for our grumpy pup.