Obesity may be factor in bone fractures

Does body fat protect you against osteoporosis or make you more vulnerable to bone fractures? A new study by the University of South Australia hopes to shed light on this question.

The issue is becoming more pressing as more than one million Australians already suffer from bone density loss – a number expected to increase as our population ages.

Researchers at the university are recruiting 120 post-menopausal women – both lean and overweight – to test how a person’s body composition influences how they process calcium to protect against bone loss and fractures.

“We know how much daily calcium someone needs to consume to help protect against bone fractures later in life. However, it is not known whether the recommended level or type of dietary calcium should be adjusted depending on someone’s body weight or their body composition,” says PhD candidate Deepti Sharma.

“People who are obese may have poor quality bones and may need to adjust their calcium intake to account for this.”

The trials form the second stage of Sharma’s thesis which also looks at the role of vitamin D in bone health. She has undertaken clinical trials of 111 hospital patients with hip fractures who are undergoing surgery and analysed their bones for structure, gene expression and their biochemical profile.

“What we have found is that high levels of vitamin D in the blood are associated with improved bone structure.

“We have known for some time that people who have higher vitamin D levels have reduced fractures. Now we are showing that vitamin D is linked with improved activity in the bone and better quality of bone. This is something which we have not previously been able to see using standard bone mineral density tests,” she says.

Associate Professor Paul Anderson, says the findings could change clinical practice.

“Our findings not only suggest that vitamin D and calcium are essential to prevent fractures but also that both may help improve fracture healing. We now know that even if you are in your eighties, if you have high levels of vitamin D you can improve the quality of your bones.”

Published data shows that up to 58% of southern Australian women are vitamin D deficient during winter due to a lack of sun exposure. Even during summer, 42% of women are vitamin D deficient due to lifestyle factors such as avoidance of the sun and the use of sunscreen protection.

Prof Anderson says most people need to expose their face and arms to some direct sunlight when the sun is high in the sky so that the body can make vitamin D naturally.

“If that can’t be achieved, it may pay to visit your GP to get a blood test. If you are deficient in vitamin D, then taking a supplement is a safe and effective way to restore vitamin D levels.

He advised that low intensity, frequent, weight-bearing exercise was also crucial for optimal bone health.