Evaluating the effect of vitamin D supplementation on serum levels of 25-hydroxy vitamin D, 1,25-dihydroxy vitamin D, parathyroid hormone and renin–angiotensin–aldosterone system: a systematic review and meta-analysis of clinical trials

Abstract

Abstract Background Vitamin D, one of the most essential micronutrients, is crucial in various health outcomes. However, previous studies showed conflicting results and uncertainty about vitamin D supplementation's optimal dosage and duration. In this study, we aimed to evaluate the vitamin D supplements efficiency on serum levels of 25-hydroxy vitamin D (25(OH)D), 1,25-dihdroxy vitamin D (1,25(OH)2D), parathyroid hormone (PTH) and renin–angiotensin–aldosterone system (RAAS) in adults. Methods A systematic analysis of eligible and relevant randomized-controlled trials (RCT) published before April 2023 assessing the effect of vitamin D supplementations applied. The studies were identified by searching several databases, including Pubmed, Scopus, Web of Science, ProQuest, and Cochrane Register of controlled trials. Results Five eligible RCTs with 346 participants in the intervention and 352 participants in the control group were assessed in our project. According to the results, there was a substantial change in 25(OH)D (SMD: 2.2, I2: 92.3, 95% Confidence Interval (CI): 1.38–3.02, P-value: 0.048) and 1,25(OH)2D (SMD:1.23, I2: 86.3, 95% CI: 0.01- 2.44, P-value < 0.010) affected by vitamin D intervention. Regarding Parathyroid hormone (PTH), however, vitamin D intervention showed a remarkable decrease (SMD: -0.75, I2: 82.4, 95% CI: (-1.3)—(-0.18), P-value < 0.010). Moreover, sensitivity analysis showed significant publication bias in terms of 25(OH)D. Conclusion Vitamin D supplements significantly increase the serum levels of 25(OH)D and 1,25(OH)2D and decrease PTH levels. While some studies reported decreasing effect of vitamin D supplements on RAAS activity, some reported no changes.