Calcium supplements safe for brittle bones

20 February 2013

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Existing advice on the use of calcium supplements for the treatment or prevention of osteoporosis remains sound, however, consumers are reminded to ensure their calcium intake does not exceed the recommended daily amount of 1000-1300 milligrams (mg) depending on age and sex, the Australian Self Medication Industry (ASMI) said today. [1]

The advice from ASMI follows two newly published clinical studies which link very high calcium intake to an increased risk of heart disease and stroke. [2,3]

According to ASMI Regulatory and Scientific Affairs Director, Steven Scarff, Australians taking calcium supplements for bone health can be reassured that these products are a safe and effective option when used according to label directions.

"Calcium is an essential nutrient for bone health, especially in women at risk for osteoporosis.  Concerns about the impact of calcium supplements on heart health must be balanced against the large body of evidence which does not support the connection between calcium intake and heart disease or stroke." [4,5,6]

A study published in British Medical Journal (BMJ) suggested that women taking above 1,400 mg per day in calcium supplements on top of their dietary intake were 1.5 times more likely to die from cardiovascular disease than women taking 600 to 999 mg per day in calcium supplements in addition to their normal dietary intake. [2]

Another recent study, published in the JAMA Internal Medicine, suggested an increased cardiovascular risk for men - but not for women - taking high intakes of calcium in supplements (more than 1000 mg per day). [3]

Mr Scarff said while these recent studies provide valuable insights, the increased cardiovascular risk was limited to study participants taking much higher doses of calcium than recommended by expert medical bodies.

Furthermore, the BMJ study did not control for important variables around heart health in women, such as the use of hormone replacement therapies and cortisone tablets. Limitations of the JAMA Internal Medicine study include a lack of information on the duration of supplement use, which might be an important factor mediating the effect of calcium supplement on cardiovascular mortality. Also, calcium intake was only measured at baseline; therefore, a change in dietary or supplement intake during the 12 year follow-up could not be assessed.

In Australia, the recommended daily intake of calcium is 1300 mg per day for women over 50 years and for men over 70 years.1 This should be achieved through a healthy diet or from supplements where dietary intake of calcium is inadequate. [1]

"Over-supplementation of any vitamin or mineral may pose a health risk to consumers. These recent studies in BMJ and JAMA Internal Medicine show that use of high amounts of calcium can increase the risk of cardiovascular disease but they do not prove that supplements (within the recommended limits) are specifically responsible for the increased risk," Mr Scarff continued.

"What we don't want to see is people with osteoporosis, or those at increased risk of brittle bones, cutting calcium out of their supplement routine and potentially making themselves vulnerable to future fractures."

Mr Scarff encouraged Australians who are unsure about their calcium intake to talk to a qualified healthcare professional who can provide advice on nutritional needs and whether the proven health benefits are outweighed by any potential risks.

References:
1.    Department of Health and Ageing. National Health and Medical Research Council. Nutrient Reference Values for Australia and New Zealand - Executive Summary. 2005.
2.    Michaëlsson K, Håkan M, Warensjö E et. al. Long term calcium intake and rates of all cause and cardiovascular mortality: community based prospective longitudinal cohort study. BMJ 2013; 346:f228.
3.    Xiao Q, Murphy R, Houston D. et. al. Dietary and Supplemental Calcium Intake and Cardiovascular Disease Mortality. JAMA Intern Med. 2013.
4.    Heaney RP, Kopecky S, Maki KC, Hathcock J, Mackay D, Wallace TC. A review of calcium supplements and cardiovascular disease risk. Adv Nutr. 2012. Vol. 3:763-771.
5.    Prentice, R. Pettinger M, Jackson R et. al. Health risks and benefits from calcium and vitamin D supplementation: Women's Health Initiative Clinical Trial and Cohort Study. Osteoporos Int. 2013.24:567-580.
6.    Osteoporosis Australia. Building healthy bones throughout life. MJA.Vol. 2. Supplement 1. 4 February 2013.