Is Vitamin D Supplementation Useful for Weight Loss Programs? A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Background and Objectives: The controversy about the impact of vitamin D supplementation on weight loss treatment was observed in several randomized controlled trials (RCTs). This meta-analysis investigates the effects of vitamin D supplementation (cholecalciferol or ergocalciferol) on weight loss through holistic measurements of Body Mass Index (BMI), weight and waist circumference. Materials and Methods: Google Scholar, WOS, PubMed and Scopus were explored to collect relevant studies. The selected articles focused on vitamin D supplementation in overweight and obese individuals with different conditions. Eleven RCTs were included into this meta-analysis with a total of 947 subjects, with a mean of the follow-up from 1 to 12 months and different vitamin D interventions (from 25,000 to 600,000 IU/monthly of cholecalciferol). Results: The meta-analyzed mean differences for random effects showed that cholecalciferol supplementation deceases the BMI by 0.32 kg/m(2) (CI95% 0.52, 0.12 kg/m(2), p = 0.002) and the waist circumference by 1.42 cm (CI95% -2.41, -0.42 cm, p = 0.005), but does not statistically affect weight loss -0.43 kg (CI95% -1.05, +0.19 kg, p = 0.17). Conclusions: This meta-analysis lays the foundation for defining the potential clinical efficacy of vitamin D supplementation as a potential therapeutic option for weight loss programs, but further studies are needed to confirm the validity of these findings and delineate potential underlying mechanisms.