I enjoyed reading the recent article by Akhil Gupta and Lyn March on the treatment of osteoporosis.1 I especially appreciated the inclusion of the numbers needed to treat (NNTs) with antiresorptive drugs to prevent a fracture. Such measures of absolute benefit are helpful for shared decision-making with our patients. However, I was disappointed that the same care was not taken in the discussion of calcium supplementation. Here, the authors simply stated that ‘combined calcium and vitamin D supplements seem safe and effective for most people who require them’.
I agree with the authors’ concerns that the cardiovascular safety of calcium supplementation are unresolved.2,3 In this context of possible harm, I believe we need to carefully consider the purported benefits of calcium. A systematic review found that calcium supplementation has little if any effect in reducing fracture.4 There was an overall 11% (95% CI* 4–19%) relative risk reduction in total fracture, which became smaller and statistically insignificant when the authors restricted their analysis to trials at low risk of bias (4%, 95% CI –1 to 9%). For the typical person with osteoporosis, these figures will equate to large NNTs for fracture prevention – much larger than those for antiresorptive drugs – if indeed there is any real benefit at all. I struggle to see then how calcium supplementation can be deemed ‘effective for most people’ as claimed.
Brett Montgomery
Senior lecturer, General Practice
School of Primary, Aboriginal and Rural Health Care
University of Western Australia
Crawley
* confidence interval