Association Between Dietary Calcium or Dairy Product Intake and Metabolic Syndrome Risk: A Systematic Review and...

Background: Dietary calcium and dairy products are hypothesized protective factors against metabolic syndrome (MetS), yet epidemiological evidence remains inconsistent. This systematic review and meta-analysis evaluated the association between total dietary calcium intake or dairy consumption and MetS prevalence in adults. Methods: Following PRISMA 2020 guidelines, PubMed, Cochrane Library, ClinicalTrials.gov, and SCOPUS were searched through to October 2025 for eligible cross-sectional studies assessing dietary calcium or dairy intake and MetS (NCEP ATP III, IDF, or JIS criteria). Longitudinal studies, non-English articles, and pediatric populations were excluded. Quality was assessed via an adapted Newcastle-Ottawa Scale. Random-effects meta-analyses pooled fully adjusted odds ratios (ORs) and 95% confidence intervals (CIs) comparing the highest versus lowest intake categories. Results: Twenty-four studies were included (12 for dietary calcium intake, 12 for dairy products). Higher dietary calcium intake was significantly associated with lower MetS odds (pooled OR: 0.85; 95% CI: 0.80-0.91), despite substantial heterogeneity (I² = 70.1%). Higher dairy consumption was also inversely associated with MetS (pooled OR: 0.78; 95% CI: 0.72-0.85; I² = 64.6%). While small-study effects were observed for dairy, trim-and-fill analysis confirmed the robustness of the findings. Higher calcium intake further correlated with favorable profiles in individual MetS components, including blood pressure, HDL cholesterol, waist circumference, triglycerides, and fasting glucose. Conclusions: Higher total dietary calcium intake and dairy product consumption are associated with a lower prevalence of MetS in adults. However, the cross-sectional nature of the included studies precludes any inference of causality between calcium intake and MetS. Therefore, although these findings suggest a protective role of calcium-rich diets, well-designed prospective and interventional studies are warranted to clarify whether this relationship is causal.