Dietary calcium intake and the risk of stroke: Meta-analysis of cohort studies

Background and aims: Prospective cohorts are inconsistent regarding the association between dietary calcium intake and the risk of stroke. The aim was to perform a meta analysis to determine whether an association exists between them in cohort studies. Methods and results: Relevant studies were identified by searching PubMed, EMBASE and Web of Science databases that published before December 2022. Prospective cohort studies that provided relative risk (RR) estimates with 95% confidence intervals (CIs) for the association were included. Study-specific risk estimates were combined by using a random effects model. Eighteen prospective studies, including 19,557 stroke cases among 882,181 participants, were pooled in the meta-analysis. We observed a nonlinear association between calcium intake and risk of stroke (Pnonlinearity < 0.003). Compared with the lowest value of zero assumed as the reference, the RRs (95% CI) of stroke across levels of calcium intake were 0.95 (0.92, 0.98) for 200 mg/day, 0.94 (0.90, 0.98) for 300 mg/day, 0.95 (0.90, 0.99) for 500 mg/day, 0.98 (0.93, 1.03) for 700 mg/ day, and 1.04 (0.97, 1.11) for 1000 mg/day. The stratified analyses by geographic region showed nonlinear associations and indicated that the protective effect was observed in Asian countries (Pnonlinearity = 0.001) but not in non-Asian regions (Pnonlinearity = 0.047). Conclusion: This meta-analysis suggests that dietary calcium intake might play an effective role in the prevention of stroke, especially in Asian countries. Future research among Asia population should attempt to establish whether this association is causal.Systematic review registration: PROSPERO CRD42022357710.& COPY; 2023 The Italian Diabetes Society, the Italian Society for the Study of Atherosclerosis, the Italian Society of Human Nutrition and the Department of Clinical Medicine and Surgery, Federico II University. Published by Elsevier B.V. All rights reserved.