The Effect of Vitamin D Supplementation on the Severity of Symptoms and the Quality of Life in Irritable Bowel Syndrome Patients: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Abstract

Irritable bowel syndrome (IBS), a gastrointestinal disorder affecting 7-12% of the population, is characterized by abdominal pain, bloating, and alternating bowel patterns. Data on risk and protective influences have yielded conflicting evidence on the effects of alternative interventions, such as vitamin D. This review focuses on the effects of vitamin D on IBS. A systematic review and meta-analysis considered all articles published until 4 April 2022. The search for randomized controlled trials assessing vitamin D efficacy in IBS with outcomes, primary (Irritable Bowel Severity Scoring System (IBS-SSS)) and secondary (IBS quality of life (IBS-QoL) and serum level of calcifediol (25(OH)D)), was performed on six databases, Google Scholar, Web of Science, SCOPUS, EMBASE, PubMed (MEDLINE), and Cochrane Central Register of Controlled Trials. We included six trials with 616 patients. The pooled analysis found no difference between vitamin D and placebo in improving IBS-SSS (MD: -45.82 with 95% CI [-93.62, 1.98], p = 0.06). However, the pooled analysis favored vitamin D over placebo in improving the IBS-Qol (MD: 6.19 with 95% CI [0.35, 12.03], p = 0.04) and serum 25(OH)D (MD: 25.2 with 95% CI [18.41, 31.98], p = 0.00001). Therefore, further clinical trials are required to reach clinically applicable and generalizable findings.

Keywords: alternative intervention; calciferol; confidence interval; flow chart; gastrointestinal disorder; heterogeneity; mean difference; placebo; protocol; random.

Figure 1

PRISMA flow chart of the screening process [33].

Figure 2

Quality assessment of risk of bias in the studies in the meta-analysis. (A) The upper panel presents a schematic representation of risks (low = red, unclear = yellow, and high = red) for specific types of biases of each of the studies in the review [27,28,29,30,31,32]. (B) The lower panel presents risks (low = red, unclear = yellow, and high = red) for the sub-types of biases of the combination of studies included in this review [43].

Figure 3

Forest plot of the included outcomes ((A)—IBS-SSS, (B)—IBS-Qol, (C)—serum 25(OH)D). I2: I-squared; CI: confidence interval [27,28,29,30,31,32,43].

Figure 4

Forest plot of the sub-group analysis ((A)—dosage sub-group analysis, (B)—diagnostic criteria sub-group analysis) I2: I-squared; CI: confidence interval [27,28,29,30,31,32,43].

Figure 5

Forest plot of IBS-Qol after exclusion El Amrousy et al. [27]. I2: I-squared; CI: confidence interval.