The health benefits of Vitamin D supplements for older people will be put to the test in one of the largest such studies ever.  
By
Peggy Giakoumelos

Source:
17 Jan 2014 - 6:40 PM  UPDATED 19 Jan 2014 - 2:50 PM

(Transcript from World News Australia Radio)

The health benefits of Vitamin D supplements for older people will be put to the test in one of the largest studies ever on Vitamin D supplementation.

The Australian study of 25,000 people aged between 60 to 79 will look at how much Vitamin D is needed to maintain good bone health in this age group.

Peggy Giakoumelos has the details.

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There have been many studies on the use of Vitamin D supplements and its importance for bone health.

While this is an accepted fact, Associate Professor Rachel Neale of the QIMR Berghofer Medical Research Institute in Queensland says what's not known is what level is needed to maintain good bone health.

She's one of the researchers behind one of the largest studies ever to take place looking at this issue.

"What we do is randomly like tossing a coin assign half of them to take a Vitamin D tablet once a month, and the other half to take a neutral or placebo tablet once a month and they don't know which is which and we don't know which is which. And once a year we send them a short survey ask them to complete them and send it back to us. So it's pretty low impact on the people in the study but they're able to make collectively a huge impact on our knowledge."

Dr Paul Glendenning, from the Royal College of Pathologists, says along with helping to answer important questions like how much supplementation is needed, it's also likely to uncover other information.

"The importance of Vitamin D nutrition is predominantly related to its effects on maximising calcium absorption and we know that calcium absorption is important for the mineralisation of bone. So indirectly Vitamin D placement is important in maintaining skeletal integrity and reducing the risk of fractures. The effects of Vitamin D on muscle metabolism are a little more complex but there's certainly evidence, that those who are Vitamin D deficient have increased muscle weakness and there's increased rate of fall rates in individuals who are Vitamin D deficient. And there's also some randomised clinical trial data showing that if you target the appropriate population and treat them with Vitamin D you reduce fall event rates."

The present recommendation is that people will achieve enough Vitamin D with moderate sun exposure, but people who receive no sun exposure should supplement their Vitamin D intake with about 400 international units a day.

This could include people in nursing homes or in long-term hospital care, some people with darker skin, and those who are fully covered for religious reasons.

And while Vitamin D is known to help maintain bone health, it's still not certain if Vitamin D helps prevent cancer, heart disease and other illnesses.

Dr Paul Glendenning explains.

"Vitamin D receptors are present in many tissues other than the skeleton and we've assume that the metabolism of Vitamin D in those areas is important the question is, if you supplement individuals who have low circulating levels of Vitamin D do you alter other types of diseases? We don't know the answer to that. All we can say is that there have been a number of observational studies demonstrating that those individuals with the lowest levels of Vitamin D, appear to have the highest incidence of other diseases. The corollary of that is that we don't have clinical trial data available that demonstrates that by supplementing those individuals you alter disease outcome and that's what the D Healthy Study amongst other large randomised clinical trials are attempting to address in the next five to ten years."

Professor Caryl Nowson is the Chair of Nutrition and Ageing at Deakin University.

She says there is no doubt that Vitamin D helps prevents falls and fractures in older people and this benefit can be seen within a year of supplementation.

But Professor Nowson says outside of at risk groups, there's a lot of hype surrounding its use.

"I think previously it was unrecognised and people didn't worry about it and now I think things have swung a bit too much the other way. You don't need to take a supplement unless you are deficient The people that are likely to be deficient are the people that don't go outside much, older people dark skinned people. So there is no requirement at all to take a supplement, unless you are in one of those high risk groups."

Professor Neale says Australia spends $150 million a year on Vitamin D testing, despite the fact that testing is unreliable and experts don't even know what blood level to aim for.

The study will link in with Medicare records and cancer registries, to provide some answers about how exactly Vitamin D works and to determine if supplementation and monitoring of Vitamin D should become routine.

The D-Health study has sent letters to more than 200,000 thousand households hoping to recruit 25,000 people for the study.