April 21, 2011 – Calcium supplements prescribed to women – in combination or not with vitamin D – to prevent or treat osteoporosis are said to modestly but significantly increase the risk of suffering a heart attack and stroke . This is what emerges from an analysis1 of several clinical trials – conducted by Scottish researchers – involving a total of 29,000 women.
The same group of researchers had already sounded the alarm last year by publishing the results of another meta-analysis2. They were then criticized for not having taken into account studies conducted with women who took calcium in combination with vitamin D. This time, they resumed the analysis by including other clinical trials and by separately compiling the results. results in women who took only calcium and in those who also took vitamin D. They came to the same conclusion.
According to their results, those who took a calcium supplement, with or without vitamin D, saw their relative risk of having a heart attack or stroke increase by 15%. If we only take into account the risk of having a heart attack, this proportion rises to 24%.
Study data indicates that if 1,000 women take a calcium supplement (with or without vitamin D) for osteoporosis over 5 years, 6 of them will have a heart attack or stroke. . In comparison, 3 of them will have avoided a bone fracture.
A modest risk
Jean-Yves Dionne
Pharmacist Jean-Yves Dionne specifies that calcium supplements may especially have a harmful effect in those who are already conducive to the onset of cardiovascular disorders. “In a huge cohort of people with very low cardiovascular risk, we will not see any adverse effect following calcium treatment, while the same treatment could very well tip several subjects into cardiovascular disease if we is dealing with a cohort of people at high risk. “
Vitamin K deficiency?
Jean-Yves Dionne adds that the data from the study tend to confirm that “taking a nutrient in pharmacological doses, and continuously, can have the effect of creating deficiencies or insufficiencies in other nutrients or ‘exacerbate the effects of an existing deficiency of a specific nutrient’.
In this specific case, it is perfectly possible that the calcium supplements exacerbated the perverse effects of vitamin K deficiency or insufficiency, he believes. It is known that vitamin K acts on calcium transporters and that a deficiency in this vitamin leads to a physiological accumulation of calcium, in particular in the blood vessels, which increases the cardiovascular risk. However, vitamin K deficiency is very common in our populations, probably because we eat too few foods that are rich in it, for example green vegetables and fatty fish.
According to Jean-Yves Dionne, researchers are right to conclude that there is a need to review the practice of systematically prescribing calcium to women at risk of osteoporosis. Increased vitamin K intake might be better advised than supplementing calcium, he argues, especially since vitamin K deficiency, even if asymptomatic, can accelerate the progression of osteoporosis.
Pierre Lefrançois – PasseportSanté.net
1. Bolland MJ, Gray A, Avenell A, et al. Calcium supplements with or without vitamin D and risk of cardiovascular events: reanalysis of the Women’s Health Initiative limited access dataset and meta-analysis. BMJ 2011; 342: d2040.
2. On this subject, see our new Calcium Supplements and Risk of Heart Problems: Caution.
