|Figure 16. Keeping active can maintain bone mass.|| |
| ||There is much epidemiological evidence linking inactivity to the risk of hip fracture. The link is due both to an increase in the risk of falling with lack of exercise and to an increase in the rate of bone loss. There is a dynamic balance between the resorption and rebuilding of bone (see 'The turnover of bone mineral' on page 2) and the effect of load-bearing exercise is to encourage bone formation. Lack of exercise tilts the balance towards resorption causing the net rate of bone loss to increase. |
Adopting a more active lifestyle is generally helpful. Everyday bone loaders, such as stair climbing, are good for improving bone density in the spine and hip in older women. A variety of brief, energetic weight-bearing activities stimulate bone to improve, although not all forms of exercise (e.g. swimming) are useful for increasing bone density.
| ||If the calcium balance in the plasma is to be maintained without calcium being resorbed from the bones there must be an adequate amount of calcium in the diet. A calcium-rich diet, such as that recommended by the National Osteoporosis Society helps to prevent bone loss. Calcium supplements are also available.|
| ||Vitamin D deficiency is an important cause of bone loss in the elderly. The role of vitamin D in calcium homeostasis has been explained in Box 2 on page 4. It is necessary for the absorption of calcium from the intestines and inhibits PTH release from the parathyroid glands. A fall in the level of calcium in the plasma stimulates the secretion of parathyroid hormone. |
Lack of vitamin D has a further effects e.g. a deficiency of vitamin D causes muscle weakness, so increasing the risk of falling.
| ||There is a well-established relationship between cigarette smoking and low peak bone mass. It has been shown that smoking increases the rate of bone loss in women after the menopause. However, the impact of cigarette smoking on the risk of osteoporotic fracture is not nearly as great as its impact on lung or heart disease.|