Effects of Vitamin D Supplementation on General and Central Obesity: Results from 20 Randomized Controlled Trials Involving Apparently Healthy Populations

Abstract

Background: The obesity pandemic has been paralleled by a high prevalence of vitamin D deficiency (VDD). There is growing epidemiological evidence linking low vitamin D status with obesity events. In addition, observational studies also show that obesity may increase the risk of VDD. However, there is insufficient knowledge to understand whether there is a causality between the two. Moreover, the impact of vitamin D supplementation on obesity indices has shown inconsistent outcomes. Objective: This meta-analysis aimed to assess whether vitamin D supplementation modified general and central obesity indices in apparently healthy populations. Methods: A systematic retrieval of relevant randomized controlled trials (RCTs) was undertaken using Pubmed, Embase, Web of Knowledge and Chinese National Knowledge Infrastructure databases. The pooled weighted mean difference (WMD) and 95% confidence intervals (CI) were used to assess the changes in body mass index (BMI), waist circumference (WC), waist-to-hip ratio (WHR) and 25-hy-droxyvitamin D (25[OH]D) from baseline. Results: Twenty RCTs involving 3,153 participants reporting either BMI, WC, WHR or 25(OH)D met the inclusion criteria. When compared with placebo, vitamin D supplementation had no significant decreases in BMI (WMD =-0.09 kg/m 2 , 95% CI-0.19 to 0.01, p = 0.08), WC (WMD =-0.71 cm, 95% CI-1.58 to 0.16, p = 0.112) or WHR (WMD = 0.00, 95% CI-0.01 to 0.01, p = 0.749). However, in the subgroups of females, Asia region studies and intervention duration ≥6 months, a beneficial and significant reduction in BMI and WC was noted (all p < 0.026). On the other hand, pooled results showed that there was a significant increase in serum 25(OH)D levels (WMD = 13.20 ng/mL, 95% CI 9.83-16.58, p < 0.001) after vitamin D intervention. No publication bias was found in our study. Conclusions: Overall, supplementation with vitamin D produced no significant effect on the BMI, WC or WHR of healthy adults.

Efficacy of Vitamin D Supplementation in Addition to Aerobic Exercise Training in Obese Women with Perceived Myalgia: A Single-Blinded Randomized Controlled Clinical Trial

“…Additionally, here we found that group B had the lowest improvement in BMI. The improvement in this group might be to the effect of a balanced low-calorie diet only as the vitamin D supplementation alone had no significant effect on BMI; this was in line with the recent systemic review that reported that despite increased serum 25(OH) D levels, the obesity indices (BMI, Waist Circumference and Waist hip Ratio) did not improve [55].…”

Investigating the Potential for Ultraviolet Light to Modulate Morbidity and Mortality From COVID-19: A Narrative Review and Update

“…Other meta-analyses suggest that vitamin D supplementation may have beneficial effects on adiposity in certain populations, with sub-group analyses of 20 randomized clinical trials (n = 3,153 participants) suggesting reduced body mass index and waist circumference in women living in Asian countries supplemented for ≥ 6 months (243). Multi-omic analyses of published datasets have identified vitamin D (among a suite of other candidates) as a potential prophylactic agent for COVID-19 (244).…”

Vitamin D Deficiency and Depression in Obese Adults: A Case- Control Study

“…It has been proposed that an inverse relationship exists between vitamin D serum levels and BMI (21). As was pointed out in the introduction to this paper, low serum 25(OH)D in obese patients can occur for a number of reasons including insu cient vitamin D consumption, increased fat or muscle mass, genotype variation in vitamin D binding proteins or enzymes responsible for vitamin D metabolism (11,13). On the other hand, vitamin D de ciency can increase the risk of developing depression, through several biological pathways including effects on immunomodulation, cellular signaling, modulation of hypothalamic-pituitary-adrenal axis, intracellular calcium homeostasis, and production of neurotransmitters(6, 22) Moreover, both obesity and vitamin D de ciency lead to a chronic low-grade in ammation, which has been suggested to contribute to the development of depression (11,23).…”

“…It has been demonstrated that vitamin D de ciency is 35% more likely in obese people compared to the healthy-weight subjects (12).Volumetric dilution of Vitamin D is the most plausible mechanism of low 25(OH)D in individuals with obesity (11). Alternative mechanisms for lower 25(OH)D concentrations in patients with obesity include lower dietary consumption, decreased dermal synthesis, reduced intestinal absorption, altered metabolism, as well as less sunlight exposure due to lower physical activity (13).…”