Suplementação de vitamina D em indivíduos com síndrome metabólica

Abstract

Metabolic syndrome (MetS) is a set of metabolic disorders, including insulin resistance, atherogenic dyslipidemia, central obesity and hypertension. Vitamin D deficiency has been observed in individuals with MetS. The thesis presented was composed of two studies, the first, a systematic review (study 1) and the second, clinical study of intervention (study 2). These studies aims to evaluate the effects of vitamin D supplementation (VDS) in individuals with MetS. The systematic review (study 1) was conducted with randomized clinical trials (RCTs), following the criteria of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and the synthesis without metanalysis (SWiM) guidelines. The searches were performed in the EMBASE, MEDLINE, Web of Science, Lilacs, the Cochrane Central Register of Controlled Trials, clinicaltrial.gov, and Google Scholar databases, considering the period from 1998 to May 2022 and using MeSH terms. The risk of bias assessment was performed using the Cochrane Risk of Bias 2.0 (RoB 2) tool. The primary outcome considered was the effect of VDS on the lipid profile (triglycerides and HDL-c) and the secondary outcomes were fasting blood glucose, blood pressure and waist circumference (WC). The Grading of Recommendations, Assessment, Development and Evaluations (GRADE) approach was applied to assess the certainty of the evidence. Clinical study of intervention was carried out with 23 individuals diagnosed with MetS, and 25(OH)D ≤ 20 ng/mL. Vitamin D supplementation was performed in two phases. In the first, 50,000IU/week was administered for eight weeks and in the second, 7,000IU/week for 12 weeks. As a result of systematic review, were included seven RCTs, with the sample sizes ranged from 50 to 120 participants. All RCTs reported a significant increase in 25(OH)D in the intervention groups. However, only two RCTs reported a significant decrease in triglycerides (TG) and WC. Among the included studies, three had a low RoB score, and three were classified as having some concerns because of domain deviations from the intended intervention, and one had a high RoB. The certainty of the evidence for primary outcomes provided very low evidence to decrease TG and increase HDL-c after VDS. Regarding secondary outcomes, we observed low certainty of evidence to decrease WC and a moderate degree for decreased fasting blood glucose level and improved blood pressure. In study 2, a significant increase in 25(OH)D (26.42 ng/mL) was observed after eight weeks of intervention; and 14.27 ng/mL after 20 weeks of intervention. The intervention lasting 20 weeks resulted in an increment of 12.1 ng/mL of 25(OH)D and HbA1c showed a reduction of 0.69%, however, it was not responsive in the MetS components. The findings of the two studies emphasize the importance of vitamin D supplementation in individuals with MetS for the correction of vitamin D status with benefit in reduce HbA1c but are inconclusive regarding the benefit in the diagnostic components of MetS.