Administration of dietary antioxidants for patients with inflammatory bowel disease: A systematic review and meta-analysis of randomized controlled clinical trials.

OBJECTIVE: Accumulating evidence has been reported regarding the effect of dietary antioxidants on clinical variables in IBD patients, however, findings are controversial. This systematic review and meta-analysis aimed to investigate effect of dietary antioxidants on clinical variables in patients with IBD or its subtypes. METHODS: We searched PubMed, Scopus, and ISI Web of Science from inception to January 2021 using relevant keywords. Data were pooled by using the random-effect model. All statistical analyses were done using STATA version 14. RESULTS: Our meta-analysis was exclusively done on studies about the effect of curcumin on IBD patients, because limited studies were done on other antioxidants. Curcumin administration resulted in significant increment of clinical remission in patients with IBD (SMD: 0.86%, 95% CI: 0.16, 1.56, p = 0.016), significant remission in clinical symptoms (SMD: -0.96 score, 95% CI: -1.34, -0.57, p < 0.001), and significant increment in endoscopic remission in IBD patients (SMD: 0.51%, 95% CI: 0.16, 0.85, p = 0.004), comparing to control group. Curcumin supplementation also made better clinical response than control group (SMD: 0.74%, 95% CI: 0.22, 1.26, p = 0.005) and also resulted in significant improvement in quality of life of patients with IBD, as compared to control group (SMD: 1.23 score, 95% CI: 0.72, 1.74, p < 0.001). CONCLUSIONS: Our meta-analysis showed that curcumin significantly improved clinical and endoscopic remissions in IBD patients. This supplementation also caused significant reduction in clinical symptoms of IBD patients along with better clinical response and the increased quality of life. Further researches with larger sample size and longer period of intervention are required to evaluate efficacy of dietary antioxidants on clinical variables in patients with IBD.

Effects of melatonin supplementation on oxidative stress: a systematic review and meta-analysis of randomized controlled trials.

OBJECTIVES: Previous studies showed that melatonin supplementation may suppress oxidative stress, however, the results have not been consistent. So, we conducted this meta-analysis to assess the precise relationship between melatonin supplementation and oxidative stress. METHODS: PubMed and Scopus were searched for randomized controlled trials that investigated the effect of melatonin supplementation on oxidative stress up to March 2020. Heterogeneity was assessed by Cochran's Q test and I-square (I 2) statistic. Data were pooled using the random effect model and standardized mean difference (SMD) was considered as the summary effect size. Also, standard methods were used for assessment of sensitivity analysis and publication bias. RESULTS: We included 15 related articles and our findings indicated that melatonin supplementation significantly increased total antioxidant capacity (TAC) level (SMD: 1.03, 95% CI: 0.24, 1.81, p=0.011) and reduced protein carbonyl (PCO) (SMD: -1.78, 95% CI: -2.97, -0.58, p=0.004) and malondialdehyde (MDA) levels (SMD: -0.94, 95% CI: -1.48, -0.40, p=0.001). Additionally, there was considerable effect on TAC level by using ≥20 mg/d melatonin and in people under 35 years old. MDA level also decreased using dosage of below 20 mg/d and in people ≥35 years old. CONCLUSIONS: The present study showed a promising effect of melatonin administration for reducing MDA, PCO, and increasing TAC levels. However, further studies especially with more attention to PCO level assessment are needed to confirm the findings of the present study in larger samples on different populations.