Dietary calcium intake in relation to metabolic syndrome in adults: A systematic review and dose-response meta-analysis of epidemiological studies with GRADE assessment.

Numerous studies have examined the relationship of calcium intake and metabolic syndrome (MetS) in adults in previous decades; but the results were inconsistent across different societies. This systematic review and dose-response meta-analysis assessed the relation between calcium consumption and MetS in adults. We did a systematic search of all articles published up to July 2023 in Scopus, PubMed/Medline, ISI Web of Science electronic databases, and Google Scholar. Observational studies investigated the association between dietary calcium (Ca) intake and MetS in adults were eligible to be included. For computing the estimates, a random effects model was applied. Combining 24 effect size from 17 investigations (15 cross-sectional and two cohort studies) with 74,720 participants and 18,200 cases showed that highest versus lowest level of dietary Ca intake was related to 23% significant decreased odds of MetS (OR = 0.77; 95% CI: 0.66, 0.89). Linear dose-response analysis of estimates from 12 investigations showed that each 100 mg/day increment in dietary Ca intake was associated with 3% marginally significant decreased odds in MetS (OR = 0.97; 95%CI: 0.93, 1.01). In nonlinear dose-response analysis of 12 studies with 67,896 participants, a significant association between dietary calcium intake and MetS was found (P <0.001); such that 500 mg/day dietary calcium intake was related to maximum decrease in odds of MetS. According to this meta-analysis, the likelihood of MetS was significantly lower in adults with higher level of dietary calcium intake. Further large-scale prospective cohort investigations are needed to obtain stronger and more accurate results.