Bone densityBone mineral density · BMD

The mineral content packed into bone: the standard marker of fracture risk.

Bone mineral density is how much mineral is packed into a given area of bone, usually measured by a DEXA scan of the hip and spine. It is reported as a T-score comparing you with a healthy young adult, with osteopenia and osteoporosis defined by thresholds on that scale.

It matters because low density raises fracture risk, and fractures in later life are not a broken bone but a turning point: hip fracture in particular carries substantial mortality and a high chance of never returning to previous independence.

Bone is living tissue in constant turnover, with osteoclasts removing old bone and osteoblasts laying down new. Peak bone mass is reached in the twenties, holds for a while, and then declines, sharply in women around the menopause as oestrogen falls.

It responds to load, and specifically to the size and rate of strain rather than to time spent moving. That is why walking and swimming, excellent for many things, do not reliably change density, and why heavy resistance and impact work do.

The LIFTMOR trial is the clearest demonstration. Postmenopausal women with osteopenia and osteoporosis did eight months of supervised twice weekly high intensity resistance and impact training, improved bone density and physical function, and had no adverse events, in exactly the population usually told that heavy loading is unsafe.

Nutrition is permissive rather than stimulating: adequate calcium, vitamin D and protein are necessary inputs, and exceeding sufficiency adds nothing. Falls prevention matters as much as density, because balance and strength are what stop a fall from becoming a fracture.

In practice, load bone heavily and progressively while you can, keep doing it as you age, and treat a low DEXA result as a reason to start supervised strength training rather than to avoid it.

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