How bone works and changes over time

Bone is not inert scaffolding. It is continually remodelled by cells that dissolve old bone and cells that build new bone. Through childhood and adolescence, building outpaces removal, and roughly 90% of peak bone mass is reached by the late teens, with the peak around the late twenties.

From then on, the balance gradually tips toward loss. In women, loss accelerates markedly in the years around and after menopause because oestrogen, which restrains bone breakdown, falls. Men lose bone more gradually but are still at risk, and men who fracture a hip have worse outcomes on average than women.

  • Osteopenia — lower than normal bone density, not yet osteoporosis.
  • Osteoporosis — density low enough that fracture risk is substantially increased.
  • Fragility fracture — a break from a fall at standing height or less, which itself indicates fragile bone.

Loading: the strongest signal for bone

Bone adapts to the forces placed on it. That makes mechanical loading the most direct lever available. Two types matter most: weight-bearing impact and resistance training.

Swimming and cycling are excellent for cardiovascular health but do relatively little for bone because they do not load the skeleton. That is not a reason to stop them, only a reason to add something else.

  • Walking helps, though brisker walking with some hills or stairs helps more.
  • Jumping, hopping, and skipping provide strong stimuli — appropriate only if joints and existing bone health allow, so check first.
  • Resistance training loads bone through muscle pull; progressive load matters.
  • Balance training reduces falls, which matters as much as density for preventing fractures.

People with established osteoporosis need modified programmes — high-impact work and loaded spinal flexion may be unsuitable, so seek individualised guidance.

Calcium, vitamin D, and protein

Calcium is the mineral in bone, and adequate intake supports maintenance. Typical adult guidance is around 1,000 mg a day, rising to roughly 1,200 mg for older women and older men. Food sources are preferred: dairy, fortified plant milks, tinned fish with bones, tofu set with calcium, leafy greens, and beans. Very high supplemental doses have not shown clear fracture benefit and have raised questions about other risks, so supplementing is best guided by a clinician.

Vitamin D is needed to absorb calcium. Deficiency impairs bone mineralisation. Whether routine supplementation reduces fractures in people who are not deficient is less clear, with large trials showing limited benefit. Testing and supplementation are individualised.

Protein supports both bone matrix and the muscle that loads it. Adequate protein is associated with better bone outcomes, contrary to older concerns that protein leached calcium from bone.

Risk factors and screening

Several factors raise risk beyond age and sex. Knowing yours determines whether screening is appropriate sooner.

  • Family history of osteoporosis or hip fracture, particularly in a parent.
  • Early menopause or long gaps without periods.
  • Long-term oral corticosteroid use.
  • Smoking and heavy alcohol intake.
  • Low body weight, or a history of eating disorder.
  • Conditions affecting absorption, such as coeliac disease or inflammatory bowel disease.
  • Rheumatoid arthritis and some other inflammatory conditions.

Bone density is measured by a DXA scan, reported as a T-score. USPSTF recommends screening for women aged 65 and older, and for younger postmenopausal women at increased risk identified by a risk assessment tool. Screening for men is less clearly defined and is individualised.

Treatment and preventing fractures

When bone density is low enough or a fragility fracture has occurred, medication is often considered. Several classes exist, including bisphosphonates and other agents, and each has its own benefits, side effects, and monitoring requirements. Any decision, including dosing and duration, is made with a prescriber based on individual risk.

Preventing the fall is as important as strengthening the bone. Most fractures in older adults follow a fall, so balance training, home safety, vision correction, appropriate footwear, and a medication review all reduce fracture risk directly.

  • Remove trip hazards and improve lighting, particularly on stairs and at night.
  • Ask about a medication review — several common medicines increase fall risk.
  • Have vision checked regularly.
  • Report any fall, even without injury; it is a strong predictor of the next one.