Throughout life, cells known as osteoblasts construct bone matrix and fill it with calcium. At the same time, osteoclasts work just as busily to tear down and resorb bone. This fine balance is regulated by many factors, including systemic hormones and cytokines. Bone mass reaches its peak by the middle of the third decade of life and plateaus for about ten years, during which time bone turnover is constant, with bone formation approximately equaling bone resorption.
As our bodies age, this fine balance is lost. As the relative hormone levels shift in midlife — more drastically in women than in men — the osteoclasts gain the upper hand and bone mass begins to dwindle. Some bone is already being lost by the time women reach menopause, but the rate of loss can increase up to tenfold during the first five years after menopause.
From midlife on, bone health is threatened by an increasing imbalance between osteoblast and osteoclast coupling function.  Additionally, osteoblasts may become less active from age 60 on. Whereas trabecular (spongy-looking) bone in the vertebrae and elsewhere was formerly at risk from excess osteoclast activity, now the cortical (dense) bone of the hip, shin, pelvis, and other sites becomes more prone to damage because osteoblasts don’t make enough of it.
Weight-bearing exercise, eating a variety of healthy foods and avoiding tobacco and alcohol can help maintain healthy bones. Foods that promote bone health include mineral and vitamin sources — dark green leafy vegetables, broccoli, legumes, canned salmon, sardines — and dairy products like milk and cheese.
Scientific literature documents the need for a wide range of minerals and vitamins vital to maintaining strong, healthy bones ... including magnesium, calcium, and vitamin D. Magnesium is one of the body’s most important minerals. In bone mineral health, magnesium (or lack of it) influences the bone mineral matrix and its ability to metabolize needed minerals for repair and rebuilding.  Calcium is the most abundant mineral in the body, primarily found in bones and teeth. In bone formation, together with vitamin D, calcium forms crystals that provide strength to maturing bone. Calcium and vitamin D are also needed to maintain healthy cartilage.