Key points  

  • Bone is a living tissue and plays a structural role in the body.
  • Because it is a living tissue it continues to be renewed throughout life, with older cells being replaced by new ones.
  • Bone is made up of a protein matrix strengthened with minerals, particularly calcium and phosphorus. There is a net accretion of calcium in bones during growth.
  • Bone mass increases throughout growth until our early twenties, when peak bone mass is achieved. There is then a period of consolidation but, from the age of about 40 years, bone loss exceeds bone formation and bone mass gradually decreases.
  • Excessive loss of bone tissue leads to osteoporosis, a condition that is characterised by bone fragility and increased risk of bone fracture. Osteoporosis may lead to mobility problems and even death.
  • It is important to optimise bone mass during growth and to maintain the skeleton during adult life in order to reduce the risk of osteoporosis developing in later life.
  • A number of nutrients play a role in establishing and maintaining healthy bones, in particular, calcium, vitamin D and vitamin K. An active lifestyle is also very important.
  • Another bone abnormality, rickets, had largely been eradicated but is now evident in sub-populations of British children. It is characterised by poor mineralization of bone. The adult form of this is osteomalacia.