I take an occasional glucosamine/chondroitin supplement. I am pretty sure I get positive results.
I can't remember the last time I chewed on hard cartilage or small bones (like EVER). So I figure taking one occasionally (maybe once or twice a month) to bolster my otherwise purified diet isn't a bad idea. My doctor said studies show they can assist in the healing of tiny cartilage fractures.
I take a multiple vitamin just about as often. I also take a low-dose aspirin after a hard work-out... to prevent soreness (inflammation)... but only like one or two a week at the very most.
Somehow... somewhere... people got the idea that food or food-like products/supplements that may be useful for our bodies must be ingested daily... or at every eating event (meal). I can't imagine that is the case. Of course... humans require doses of high protein that will likely ONLY be found in eggs and meat. But do we need meat every meal?!?! Or even everyday? I wouldn't guess we would. The same could be said about dairy, leafy greens, or fruits. Maybe getting all the food groups crammed into a day... would be just as good as every group at every meal.
I take the same attitude with food supplements. Maybe after a extra long hard day of exercise or work... a little extra hydration, a vitamin/aspirin/supplement/beer, and/or a nap... might be a good healthy bit of preventive care,