Pointing the bone at osteoporosis
Box 1 | Ensuring a healthy balance at the bone bank
We can all take steps to ensure that we achieve our maximum possible peak bone mass.
Diet
A balanced diet is essential: this includes ensuring that we consume the recommended daily dietary intake of calcium. (See the tables at the end for recommended intakes and foods high in calcium.) Dairy foods like milk, cheese and yoghurt are particularly important, because they contain both a high level of calcium and a high level of lactose (milk sugar), which increases the efficiency of calcium uptake. Try low-fat dairy foods if weight or heart disease is a concern – these often contain more absorbable calcium than do whole milk products. Tinned salmon and sardines (with edible bones) also contain high levels of absorbable calcium.
Excessively thin girls and women appear to have a higher risk of developing osteoporosis, possibly due to a suppressive effect on the production of oestrogen. In addition, recent research suggests that people with more fat tend to produce more of a hormone called amylin, which has been shown to make osteoblasts grow more quickly and to 'switch off' osteoclasts.
Exercise
Scientists believe that exercise stimulates osteoblasts to be more active, increasing bone production and reshaping bones so that they have greatest strength where it is needed most. Almost any kind of exercise will help, but the most effective are those that are performed against the force of gravity (called weight-bearing exercises). These include jogging, walking, skipping, dancing, tennis, football, netball and other ball sports. An active lifestyle should begin as early as possible in life: studies have shown that active children have a 24 per cent higher peak bone mass than non-active children.
Excessive exercise may also be risky, since it may lead to a reduced production of oestrogen with subsequent negative effects on bone formation. Women whose oestrogen levels have fallen as a result of excessive exercise are sometimes given hormone replacement therapy (Box 2).
Other lifestyle issues
Smoking and excessive amounts of alcohol are both thought to contribute to the risk of osteoporosis, possibly by inhibiting the actions of hormones that aid calcium absorption. Smokers also tend to have a thinner build and reach menopause earlier.
A family matter?
Scientists remain uncertain as to why some people are more susceptible to osteoporosis than others. For example, there may be hereditary factors involved: susceptibility increases in people with a family history of osteoporosis. Australian scientists are involved in research to track down genes that may contribute to the treatment or prevention of the disease.
Recommended daily allowances of calcium
| Girls | up to 7 years 8-11 years 12-15 years 16-18 years |
800 mg 900 mg 1000 mg 800 mg |
| Women aged 19-54 years Menopausal women and women over 54 years Pregnant women Breastfeeding women |
800-1000 mg 1000 mg 1100 mg 1200 mg |
|
| Boys | Up to 11 years 12-15 years 16-18 years |
800 mg 1200 mg 1000 mg |
| Men 19 years and over | 800 mg | |
Source: National Health and Medical Research Council
Some foods with a high calcium content
| Product | Serve | Calcium (milligrams) |
| Milk and milk products Whole milk Skim milk Modified, low fat milk (eg, Shape, Fitness) Modified, reduced fat milk (eg, Hi Lo, Rev) Yoghurt – natural Cheese – Swiss – Cheddar – Mozzarella, Edam |
250 ml (1 cup) 250 ml (1 cup) 250 ml (1 cup) 250 ml (1 cup) 200 g (1 carton) 25 g (1 slice) 25 g (1 slice) 25 g (1 slice) |
290 310 410 350 285 240 215 180 |
| Soy products Fortified soy milk (eg, So-Good) Tofu |
250 ml (1 cup) 200 g |
290 240 |
| Tinned fish Sardines – tinned Salmon – tinned with bones |
100 g 100 g |
350 190 |
| Dishes Quiche Lorraine Cheese souffle Lasagna/cannelloni Moussaka Tahini paste Pizza Cheeseburger Fish in batter |
1 slice 100 g 200 g 200 g 25 g (1 tablespoon) ½ medium 1 100 g |
390 240 130 180 230 350 100 75 |
Source: Health Promotions Centre, Department of Community Medicine, Westmead Hospital, NSW
Box
Box 2. Hormone replacement therapy
Related site
What interventions are effective in preventing osteoporosis and osteoporotic fractures? (Medical Journal of Australia)
Page updated July 2002.