Calcium intake and gastric cancer risk: A systematic review and dose-response meta-analysis of observational studies

Calcium has been proposed as a protective factor against certain types of cancer, but findings related to gastric cancer (GC) are inconsistent. This meta-analysis aimed to assess the association between calcium intake and the risk of GC. A comprehensive search was conducted in PubMed, Scopus, EMBASE, LILACS, and Web of Science for cohort and case-control studies published up to August 19, 2024. The quality of the studies was assessed using the Newcastle-Ottawa Scale. Publication bias was tested using Egger's and Begg's tests. Relative risks (RRs) and 95 % confidence intervals (CIs) were pooled through a random-effects model. Given the substantial heterogeneity and potential variation in intake levels across populations, a dose-response analysis was conducted to explore potential trends across the full range of calcium consumption. Thirteen studies involving 1,610,992 participants met the inclusion criteria. A non-significant inverse association was observed between total calcium intake and GC risk when comparing the highest vs lowest intake categories (RR: 0.85; 95 % CI: 0.70-1.05). While this categorical comparison was not statistically significant, the dose-response analysis revealed a significant linear protective effect, with a 10 % reduction in risk per 300 mg/day increase in dietary calcium intake (RR: 0.90; 95 % CI: 0.82-0.99). To account for potential variations across intake levels, a non-linear model was also applied, indicating a clearer risk reduction above 400 mg/day (p for non-linearity < 0.001). Overall, this dose-response meta-analysis suggests that higher dietary calcium intake may have a protective effect against GC, reinforcing the importance of considering calcium in dietary strategies for GC prevention, although more studies are needed to confirm these findings.