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Boning up

What are the recommended ways of improving bone strength?

Anyone can potentially develop osteoporosis, but some are at more risk of the bone-weakening disease than others. And your chances could be greater if you are older, are post-menopausal, have pale skin, are slight of stature, don’t get much calcium through your diet or avoid exercise.

Once again, the health message for those who don’t have a specific disorder that reduces bone strength is pretty simple. Eat a good diet, exercise regularly, keep to a good weight, don’t smoke. Then, when you get to 65 if you’re a woman or 70 if a man, check with your doctor.

Getty Images.
Getty Images.

Yet many people take calcium and vitamin D supplements in the belief they help their bones. Do they?

Calcium supplements were recommended for a long time, says Dr Mark Bolland, an endocrinologist for Counties Manukau DHB and a researcher into bone diseases at the University of Auckland. However, the results of clinical trials now suggest they may reduce your relative risk of suffering a fracture by about 10% but also increase your relative risk of heart attacks by 20% and stroke by 15-20%, he says. They also increase the risk of kidney stones, constipation and gastric problems generally. “Overall, the risks of them are probably greater than the benefits that you get.”

Vitamin D was also typically recommended. Dietary sources – oily fish, cheese, egg yolks, mushrooms – are generally poor, he says. Foods are sometimes fortified with it overseas but rarely here. Sunlight is the main source of vitamin D by far, Bolland says. The skin synthesises cholesterol via ultraviolet B light into vitamin D. The vitamin helps the body absorb calcium – although too much can be harmful. To get it from the sun you need only spend about 10-15 minutes a few times a week in our ozone-unfiltered sunlight, ideally exposing your arms and legs. For frail people, those who actively avoid the sun or who have deeply pigmented skin – melanin reduces the skin’s ability to make it – vitamin D supplements may help. But the bottom line is that the supplements are “fairly ineffective for older people who are otherwise in good health”.

Some drugs help with osteoporosis, bisphosphonates being the most common. They inhibit cells that contribute to bone loss. In a tablet form, there’s alendronate, brand name Fosamax, or risedronate, and more recently an injection, zoledronate, also known as Aclasta.

They are quite effective, Bolland says. “They will reduce fractures by a third or a quarter, overall, and hip fractures by about a half.” But it would be good to have other options, he says. Bisphosphonates have side effects, including gastric problems.

Smoking is bad for bones. Alcohol also affects the body’s absorption of calcium, although it’s physiological effect is probably minor, Bolland thinks: if you drink a lot you tend to fall more.

Exercise, particularly putting your muscles and bones under some strain, is generally recommended, although the evidence is not direct. Improved bone density has been demonstrated, but whether this translates into preventing fractures is not certain.

As women’s oestrogen levels drop after menopause, bone density levels tend to drop also. But many are wary of hormone-replacement therapy (HRT), after research a decade ago found that treatment with oestrogen and progesterone increased the risk of heart attacks, breast cancer and blood clots. There has always been good evidence, however, that HRT prevents fractures as effectively as bisphosphonates, says Bolland.

Oestrogen-only trials found some increase in blood-clot risk but none of the other harms. The general view is oestrogen probably shouldn’t be taken long term as a preventative agent, he says, but for a small number of women the benefits to their bones probably outweigh the risks. And around menopause, oestrogen is still recommended.

Testosterone levels in men also decrease with age and this affects bone density, but it tends to be at very low levels, says Bolland. Some prescription drugs also have an impact on bones, particularly certain types of steroids.

There is such a thing as peak bone mass, which we tend to reach in our late twenties to early thirties. But healthy young people shouldn’t be greatly concerned about their bones, he says. “People have got lots of other things to worry about.”

Health Briefs


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