Glucosamine. Image credit Hopkins Arthritis Foundation.
Here's the study (here's the original journal article). Bottom line, there was a double-blind placebo-controlled study done of glucosamine in lower back pain in osteoarthritis. Glucosamine didn't do any better than placebo. That is, it was the same as not taking anything.
I was eager to post this because so many runners swear by glucosamine and related supplements - often uncritically. (For instance, are you taking it to alleviate pain, or to make your joints stronger? Never made that distinction before, huh? Most people don't.) And of course you can't generalize a single study to all effects of glucosamine in all settings. So maybe (for example) glucosamine might be better for knees than backs, maybe it's better in healthy athletes than in osteoarthritis patients. The way to find this out is from studies; that's how you cut through marketing hype and our own biases.
Before we get to the evidence, there's an important point there - it's often hard to filter out real evidence from promotion. Always remember that there is a lot of money in supplements, with lots of vested interest in not asking tough research questions. It's a multi-multi-billion dollar a year industry. And since these aren't legally defined as drugs, the standard of evidence for these companies' claims is basically nonexistent. This is why you should be very cautious of any statistics reported in running magazines or especially "alternative" or herbal pharmacies!
As a side note: it's very frustrating to hear people talk about evil pharmaceutical companies, when those companies provide evidence, and then these same people will slap fifty bucks down at a fancy pharmacy for evidence-free grass clippings in a bottle because they're "herbal". The supplement manufacturers are happy to let you keep believing, and they're also happy to sue anybody who they perceive as threatening their business with pesky evidence and studies. I would love to get publicity from them trying that after this blog post but I doubt this will come to their attention. I'm all for people making profits, but when someone else's profit motive interferes with my own desire to make health decisions based on evidence - well, guess which one wins.
So (drum roll) what does the no-nonsense, peer-reviewed, publicly accountable, non-conflict-of-interest evidence say? When you gather together the studies so far, there isn't much reason to believe that they do anything to help fix cartilage. On the other hand, several other reviews say there is maybe some spotty effect on pain (again, these are studies in osteoarthritis patients). If all it's doing is helping with pain relief, then I'll stick with my well-studied, cheap ibuprofen.
You might be reading this and thinking "Well, I take glucosamine and I know it works for me." And some of the people in the placebo group of that back pain study certainly improved on their own, and were dutifully convinced that they were in the group getting glucosamine. "But I'm really sure." So were they. This is why you do placebo-controlled studies. In my previous career as a clinical research professional, I worked on multiple double-blind studies where even the doctor didn't know what s/he was dispensing, and after the study the doctors always wanted to know which patients got what. And usually, even the doctors guessed worse than random chance.
So if you want to keep taking it, what's the harm? Besides to your pocketbook, none. Glucosamine and related supplements seem to have no side effects, although most of the glucosamine you take goes into your blood as sugar, not as glucosamine. So if you're on a low carb diet, think hard about that the next time you're taking your dose.