The effects of vitamin D intake and status on symptom severity and quality-of-life in adults with irritable bowel syndrome (IBS): a systematic review and meta-analysis.

IMPORTANCE: Many individuals with irritable bowel syndrome (IBS) have insufficient or deficient serum 25-hydroxyvitamin D [25(OH)D] status; however, it is not clear if improved vitamin D nutritional status through higher intake can improve symptom severity and quality of life. OBJECTIVE: This systematic review and meta-analysis aimed to identify if changes in vitamin D intake or status affect symptom severity and quality of life in adults with IBS.Data Sources: MEDLINE®, Cochrane Central Register of Controlled Trials, Global Health, EMBASE, and Web-of-Science databases were systematically searched for relevant articles to August 12, 2024, in the English language.Study Selection: Clinical trials, prospective observational studies, and Mendelian randomization (MR) analyses reporting the effect of vitamin D intake or status on IBS-related outcomes were included.Data Extraction and Synthesis: Article review and data extraction were conducted by 2 authors following the PRISMA guidelines. Random effects meta-analyses and the Nutrition Quality Evaluation Strengthening Tools to assess risk of bias were employed for randomized controlled trials.Main Outcome(s) and Measure(s): Primary outcomes included measures of serum 25(OH)D status, symptom severity, and quality of life. RESULTS: 12 studies from 15 articles were included (n = 7 RCTs; n = 3 single-arm interventions; n = 2 MR). Seven study populations had deficient (<20 ng/mL) and three had insufficient (21-29 ng/mL) baseline serum 25(OH)D status. RCTs measured changes in serum 25(OH)D after 6-26 wks with 3,000 IU daily to 50,000 IU bi-weekly vitamin D dosages. Meta-analyses of low risk-of-bias RCTs revealed increased 25(OH)D levels in groups treated with oral vitamin D compared to placebo (n = 5; Pooled mean difference [95% CI]: 20.33 [12.91, 27.74] ng/mL; I2 = 97.9%). Quality of life scores improved significantly in deficient populations (n = 3; 3.19 [2.14, 4.24]; I2 = 0.0%). Non-significant decreased trends in IBS symptom severity were shown across populations (n = 6: -25.89 [-55.26, 3.48]; I2 = 92.8%). CONCLUSION: Moderate level evidence indicate vitamin D supplementation may improve status in adults with IBS and quality of life in those with deficient status at baseline.