Adequate calcium intake may lower stroke risk

A new review from Sweden suggests that increased dietary calcium intake may be associated with a reduced risk of developing stroke in populations with low to moderate calcium consumption.

The meta-analysis included 11 prospective studies which examined calcium intake and cases of stroke in a total of 9,095 participants (1). The analysis showed that among participants who consume low to moderate average amounts of calcium (less than 700 mg/day) a 300-mg/day increase in calcium intake was associated with an 18% reduction in stroke risk. Among Asian populations, the risk of stroke decreased by 22% for each 300-mg/ day increase in calcium intake. The association between calcium intake and stroke did not differ appreciably by stroke types.

The researchers commented that dietary calcium intake differed substantially between studies: in the Asian populations, calcium intake was much lower than in the European populations and somewhat lower than in the US studies. This may explain the inconsistent findings across populations. In an analysis of calcium sources, intake of calcium from dairy foods (the major sources of calcium in European and American populations) was associated with risk reduction of stroke. But this was not the case for calcium in nondairy foods (the main contributors to calcium in Asian populations). This finding might suggest that it is not calcium alone that is beneficial, rather the association could be explained by other factors, such as other minerals (e.g., potassium), vitamins (e.g., vitamin D in fortified milk) or a combination of nutrients in dairy foods.

Evidence from experimental studies in vitro and in vivo indicates that calcium may lower the risk of cardiovas-cular disease via multiple mechanisms, for instance, through effects on blood cholesterol concentrations, blood pressure, insulin secretion and sensitivity, inflammation, thrombosis, and obesity (2). However, results from observational prospective studies and randomized controlled trials of calcium intake and calcium supplementation, respectively, and stroke risk have been conflicting. One of the differences between the observational studies and randomized trials is the dose of calcium intake, which was significantly higher in the clinical trials.

1. Larsson S. C. et al. Dietary calcium intake and risk of stroke: a dose-response meta-analysis. AJCN. Published online April 2013.
   
2. Wang L. et al. Calcium intake and risk of cardiovascular disease: a review of prospective studies and randomized clinical trials. Am J Cardiovasc Drugs. 2012; 12:105–116.