An exhaustive scientific review, released today, has concluded that upping calcium intake through food or supplements is unlikely to improve bone health or prevent fractures in older people.
Two papers, published in the British Medical Journal, should be the "final word" on what has been a debated subject over previous years, one of the New Zealand co-authors told the Herald.
The studies find that increasing calcium intake through food or supplements should not be recommended for fracture or osteoporosis prevention.
Presently, guidelines advise older men and women to take at least 1000 to 1200mg per day of calcium to improve bone density and prevent fractures, and many people take calcium supplements to meet these recommendations.
In New Zealand pharmacies, bottles of calcium supplements marketed specifically for bone health retailed for prices up to $46.
But recent work led by researchers including Distinguished Professor Ian Reid of Auckland University has questioned their effectiveness.
A paper published last year reported the global calcium supplements market was worth an annual $4 billion, but the size of the market had reduced significantly over the past few years in light of recent findings, he said.
Distinguished Professor Reid, believed that with this new review, which canvassed a large volume of scientific literature, there was little need to take the issue further.
Fellow Auckland University researcher, Associate Professor of Medicine Dr Mark Bolland, led a team to examine the evidence underpinning intake recommendations to improve bone health and prevent fracture.
They analysed the available evidence from randomised controlled trials and observational studies of extra dietary or supplemental calcium in women and men aged over 50, and the study design and quality were taken into account to minimise bias.
In the first study, the team found that increasing calcium intake from dietary sources or by taking supplements produces small - one to two percent - increases in bone mineral density, which were unlikely to lead to a clinically meaningful reduction in risk of fracture, Dr Bolland said.
"The second study found that dietary calcium intake is not associated with risk of fracture, and there is no clinical trial evidence that increasing calcium intake from dietary sources prevents fractures."
Collectively, the results suggested that clinicians, advocacy organisations and health policymakers should not recommend increasing calcium intake for fracture prevention, either by use of calcium supplements or dietary sources, he said.
"For most patients who are concerned about their bone health, they do not need to worry about their calcium intake."
In an editorial that accompanied the research, co-author Professor Karl Michaelsson of Sweden's Uppsala University said it was time to revisit recommendations to increase calcium intake beyond a normal balanced diet.
Ever increasing intakes of calcium and vitamin D recommended by some guidelines defined virtually the whole population aged over 50 at risk, he said.
"Yet most will not benefit from increasing their intake.... and will be exposed instead to a higher risk of adverse events [such as gastrointestinal side effects]".
"The weight of evidence against such mass medication of older people is now compelling, and it is surely time to reconsider these controversial recommendations."
Distinguished Professor Reid said good bone density could be maintained through simple lifestyle choices, such as keeping a balanced diet to maintain healthy body weight, not smoking and ensuring only a moderate alcohol intake.
One-size-fits-all approach shouldn't apply to older people: researcher
Dr Carol Wham of Massey University's Institute of Food and Nutrition said the findings highlighted that not enough was known about calcium needs for older people, who she described as a "heterogeneous", or diverse, population.
One-size-fits-all recommendations were not cognisant of requirements, she said, and were problematic as extrapolated from balance studies in younger adults.
"Evidence supports a food based approach but more information is needed about which dietary patterns support the best health outcomes for older people.
"For example, milk and milk products are not only important for bone health; they are key contributors to dietary protein intake which is especially important for older adults to maintain healthy function."
Dietitian Sue MacDonell, also a PhD candidate at Otago University's Department of Human Nutrition, said the Nutrient Reference Values for calcium in Australia and New Zealand was set to ensure that the amount of calcium consumed was similar to the amount lost through excretion.
"There is some evidence that aging results in both a reduction in calcium absorption and an increase in calcium loss, hence the higher calcium requirements recommended for older men and women," she said.
"These higher intakes are intended to minimise loss of calcium from bone stores."
But the most recent papers were clear in their recommendation that calcium supplements should not be prescribed to older adults on the basis of improving bone mineral density or preventing fractures.
"It is important to remember, however, that besides contributing to bone health, calcium also has other roles in the body," she said.
"For this reason it is important that the decision to prescribe calcium supplements is made based on the health needs of each person as any dietary supplement, including calcium, should only be prescribed if the person has a demonstrated need."
Dietitians agreed it could be certainly be difficult for older people to meet the higher recommendations for calcium solely from food - particularly if dairy products were not regularly consumed and consequently there are instances where calcium supplementation is indicated.
"In light of these most recent findings, physicians and dietitians should consider the appropriateness of calcium supplementation for each patient."
Considerations included the amount of calcium being consumed from dietary sources, tolerance of the supplement and other health conditions such as cardiovascular risk.
"Furthermore it is worthwhile to check that very high amounts of calcium are not being consumed from all sources combined."
"In the residential care setting, I would continue to advocate for calcium supplementation where a resident has been assessed as not meeting their calcium requirements.
"Furthermore there is strong evidence supporting supplementation of vitamin D for older adults in residential care where vitamin D levels are likely to be low. The findings of these most recent studies do not change these recommendations."
Sue Pollard, chief executive of the New Zealand Nutrition Foundation, backed the new studies, adding that views around calcium as a supplement had changed over recent years.
"Certainly, it is interesting - mostly, the recommendations for calcium intake is that it's good for you to have some sort of calcium for your diet, but as part of your diet and not as a supplement."
Consumer New Zealand chief executive Sue Chetwin said supplement claims had generally been outstripping the science, with some manufacturers "cherry-picking" the research they relied on.
"The article flags the need for manufacturers to be required to substantiate their claims to a high level so that consumers are not being misled as to any health claims and by dubious research."
Auckland dietitian Angela Berrill said the findings added more fuel to the debate around how much calcium adults over the age of 50 needed to reduce their risk of fracture.
"However, while the results are interesting, I would caution people against making any changes to their medication or dietary regime without consulting with their GP or a registered dietitian first," she said.
"It is also important to acknowledge that this research investigated the implications of dietary calcium intakes and calcium supplementation in adults aged 50 years plus - therefore, any findings are potentially relevant for this segment of the population only."
Alison Quesnel, executive director of industry group Natural Products New Zealand, echoed Ms Berrill's advice encouraging people to talk to a health practitioner before taking any dietary supplements - "and in some cases that advice may be there is no need to take anything at all".
"We would like to add that we advise that it is always best to meet nutritional needs through a healthy, balanced diet and lifestyle," she said.
"But that's not always possible."
Tim Roper, executive director of the New Zealand Self-Medication Industry Association, said he would consider the papers in depth and be responding in detail.
"My initial reaction is that it provides new research which adds to the body of knowledge about the prevention of osteoporosis," he said.
"But the results and the study need to be considered in the light of the 'body of evidence' that is already available and provides an alternative view."