BackgroundFindings of observational studies that evaluated the association of serum vitamin D status and high blood pressure were contradictory. This meta-analysis of epidemiologic studies assessed the relation of serum vitamin D levels to hypertension (HTN) and pre-hypertension in adults.MethodsWe conducted a systematic search of all published articles up to March 2021, in four electronic databases (MEDLINE (PubMed), Web of Science (ISI), Embase and Scopus), and Google scholar. Seventy epidemiologic studies (10 prospective cohort, one nested case–control, and 59 cross-sectional investigations) that reported relative risks (RRs), odds ratios (ORs), hazard ratios, or prevalence ratios with 95% CIs for HTN or pre-hypertension in relation to serum vitamin D concentrations in adults were included in the analysis.ResultsIn prospective studies, a 16% decrease in risk of hypertension was observed in participants with high levels of serum vitamin D compared to low levels (RR: 0.84; 95%CI: 0.73, 0.96; 12 effect sizes). Dose–response analysis in prospective studies revealed that each 25 nmol/L increase in serum vitamin D concentrations resulted in 5% reduced risk of HTN (RR: 0.95; 95% CI: 0.90, 1.00). Also, a significant nonlinear relationship between serum vitamin D levels and HTN was found (Pnonlinearity < 0.001). In cross-sectional investigations, highest vs. lowest level of serum vitamin D was related to reduced odds of HTN (OR: 0.84; 95%CI: 0.79, 0.90; 66 effect sizes) and pre-hypertension (OR: 0.75; 0.95%CI: 0.68, 0.83; 9 effect sizes). Dose–response analysis in these studies showed that each 25 nmol/L increase in serum vitamin D levels was related to a significant 6% reduction in odds of hypertension in all populations (RR: 0.94; 95%CI: 0.90, 0.99) and 3% in studies with representative populations (RR: 0.97; 95%CI: 0.95, 0.99).ConclusionThis meta-analysis of epidemiologic studies disclosed that serum vitamin D concentrations were inversely related to the risk of HTN in adults, in a dose–response manner in both prospective cohort and cross-sectional studies.Systematic Review Registration:http://www.crd.york.ac.uk/Prospero, identifier: CRD42021251513.

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Context Although some studies have examined the connection between circulating 25-hydroxyvitamin D (25(OH)D) concentrations and preeclampsia (PE) risk, the results were inconsistent. Objective A dose-response meta-analysis on epidemiologic investigations was conducted to evaluate the relation of 25(OH)D concentration and PE. Data Source Electronic databases, including Scopus, MEDLINE (PubMed), the Institute for Scientific Information, Embase, and Google Scholar, were comprehensively search until July 2021. Data Extraction A total of 65 observational studies evaluating the link between circulating 25(OH)D concentrations and PE were included. The body of evidence was assessed by the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) approach. Data Analysis Combining 32 effect sizes from 32 prospective studies with 76 394 participants revealed that highest vs lowest circulating 25(OH)D concentrations was significantly related to a 33% reduced risk of PE (relative risk [RR], 0.67; 95%CI, 0.54–0.83). Subgroup analysis by study design revealed that PE risk has significantly decreased in cohort and case-cohort studies (RR, 0.72; 95%CI, 0.61–0.85), and a slight decline was found in nested case-control studies (RR, 0.62; 95%CI, 0.38–1.02). Dose–response analysis in 27 prospective studies with 73 626 participants illustrated that each 10 ng/mL increment in circulating 25(OH)D concentration led to a 14% reduced incidence of PE (RR, 0.86; 95%CI, 0.83–0.90). A U-shaped significant association in nonlinear dose–response analysis was found between 25(OH)D and PE. A significant inverse association was also found between highest vs lowest circulating 25(OH)D concentration and PE in 32 nonprospective studies with 37 477 participants (odd ratio, 0.37; 95%CI, 0.27–0.52). This inverse association was significant in almost all subgroups, based on different covariates. Conclusion This meta-analysis of observational investigations showed blood 25(OH)D levels were negatively related to PE risk, in a dose-response manner. Systematic Review Registration PROSPERO registration no. CRD42021267486.

The association of plant-based diets with health status is underestimated in pediatrics. We aimed to examine the relation between plant-based diets (including overall plant-based index (PDI), healthy plant-based (hPDI) and unhealthy plant-based (uPDI)) and metabolic health status in Iranian adolescents with overweight/obesity. We conducted a cross-sectional study on 203 adolescents with overweight/obesity (12–18 years old) selected by a multistage cluster random-sampling method. Usual dietary intakes were assessed through a validated 147-item food frequency questionnaire (FFQ). Anthropometric indices and blood pressure values were measured and fasting blood samples were drawn. For classification of participants into metabolically healthy obese (MHO) or metabolically unhealthy obese (MUO) groups, two methods of International Diabetes Federation (IDF) and combination of IDF with Homeostasis Model Assessment Insulin Resistance (HOMA-IR) were applied. No significant association was observed between higher adherence to PDI and odds of MUO status defined by both IDF and IDF/HOMA-IR strategies. After adjustments for all potential confounders, adolescents in the highest tertile of hPDI, compared with those in the lowest tertile, had 85% (95% CI 0.05–0.43) and 84% (95% CI 0.05, 0.52) lower odds of being MUO based on IDF and IDF/HOMA-IR criteria, respectively. Greater adherence to uPDI was associated with odd of 3.95 (95% CI 1.41, 11.12) and 4.06 (95% CI 1.31, 12.57) of being MUO based on IDF and IDF/HOMA-IR definitions, after considering all potential confounders. Stratified analysis revealed that these associations were stronger in girls and overweight subjects. Adherence to healthy plant-based foods was inversely associated with odds of MUO status in Iranian adolescents. In contrast, unhealthy plant-based diets was directly associated with MUO in pediatrics. Further studies with prospective nature, are required to affirm these results.

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