The Effects of Supplementation with Chromium on Insulin Resistance Indices in Women with Polycystic Ovarian Syndrome: A Systematic Review and Meta-Analysis of Randomized Clinical Trials.

Recently, the effects of nutritional supplementation on improvement or prevention of polycystic ovary syndrome (PCOS) have been considered. Several studies have been carried out on the effect of chromium supplementation in improving PCOS patients. This study aimed to summarize the available findings regarding the effect of chromium on improving the polycystic ovary syndrome. The review includes randomized controlled trials (RCTs) comparing chromium treatment with placebo or other treatments in women with PCOS. Women with PCOS diagnosed according to the ESHRE/ASRM or NIH criteria in reproductive age were eligible. Electronic searches using the MeSH terms were conducted in the following databases: Medline, Embase, Scopus, Web of Science, and The Cochrane Library. Effects were measured as weighted mean difference (WMD) and 95% confidence intervals (CI) for studies of PCOS and control subjects were calculated by using random-effects model. The initial search yielded potentially 100 relevant articles of randomized clinical trials on dietary chromium supplements: 16 from Pubmed, 36 from Embase, 29 from Scopus, and 19 from Web of Science. After studying these publications, 5 were potentially eligible and retrieved in full text. The five studies included in the meta-analysis reported data on 137 women with PCOS and 131 controls. A meta-analysis of 5 studies showed a non-significant difference in fasting insulin between chromium, and placebo or other treatment (mean difference (MD): -1.14; (95% CI: -4.11 to 1.83, p=0.45). We retrieved two randomized controlled trials, in which Quantitative Insulin Sensitivity Check Index (QUICKI) was compared between chromium, and placebo or other treatment in 156 women with PCOS. Meta-analysis of two RCTs showed no significant difference in QUICKI score between chromium and placebo (MD: 0.01; 95% CI: -0.01 to 0.04, p=0.34). Two randomized controlled trials compared Homeostatic Model Assessment-Insulin Resistance (HOMA-IR) between chromium, and placebo or other treatment in 81 women with PCOS. After combining the data, there was a significantly lower HOMA-IR in the chromium group (MD: -1.68; 95% CI: -2.42 to -0.94, p<0.001). One RCT reported a significant difference in Homeostatic Model Assessment-beta-cell function (HOMA-B) between chromium and placebo groups (-15.5±32.3 vs. +13.6±23.1, p<0.001). No significant effect of chromium on fasting insulin and QUICKI score was found in women with PCOS. Chromium supplementation significantly improved HOMA-IR and HOMA-B among patients with diabetes. The magnitude of the effect is small, and the clinical relevance is uncertain. Future trials in well characterized studies that address the limitations in the current evidence are needed before definitive claims can be made about the effect of chromium supplementation.