depends on what you lack. Calcium for bone strength, however, if you already get enough, more probably won't help you much. It's all about whether you get enough of it in your diet or not.
Get a Calcium/Magnesium combination supplement. The Mg helps your digestive system absorb the calcium better. Take a VitD supplement at the same time as the Ca/Mg because the VitD helps the calcium be absorbed into your bones, and top it off with a Glucosamine/Chondroitin combination supplement for the joints.
I take this stack usually twice a week just to make sure everything stays a-o-k
Supplements come into play if you're lacking something in your diet. If you lack calcium for example, it could become a problem since the body can draw calcium from the bones, but if you've got enough in your diet to get optimal results as far as improving bone density with exercise, then getting more isn't gonna force the body's bones to get more dense quicker. Though, you can probably discuss exactly how much calcium is "enough" (as well as for other minerals and vitamins)
True, to an extent. Any impact of to your bones, especially during exercise, increases your bone density. However, in your joints, you sometimes need something extra in your diet after really intense activity in order to help them recover and reduce any possible inflammation. I take a small supplement of essential fatty acids after very high-impact workouts to help this.
Calcium to supplement the diet in regards to bone health....and as far as joints go, I've found Supercissus to be far superior to glucosamine/msm stuff; may also help bones as well, it's said to have anabolic properties