The effect of herbal extracts and plant bioactive compounds on insulin resistance in women with polycystic ovary syndrome: a systematic review and meta-analysis of randomized controlled trials

Background Herbal extracts and plant bioactive compounds have been shown to improve several metabolic outcomes. Objective We conducted a systematic review and meta-analysis of randomized controlled trials (RCT) to examine the effect of herbal extracts and plant bioactive compounds on insulin resistance (IR) in women with polycystic ovary syndrome (PCOS). Methods We searched Pubmed, Web of Science, Scopus, and LILACS from inception until February 06, 2025, for RCT addressing the effect of herbal extracts and plant bioactive compounds in women with IR. Their findings were analyzed the data qualitatively and quantitatively, the latter using a random-effects model. Main results Among the 39 included RCT, curcumin (n = 6, 350 women), cinnamon (n = 5, 217 women), and berberine (n = 3, 236 women) were the most frequently assessed herbal extracts/compounds. In the qualitative analysis, most of them had a beneficial effect on IR in women with PCOS. However, synthesis of their findings indicated that curcumin had a neutral effect on HOMA-IR (standardized mean difference, SMD: -0.07, 95%CI: -0.34, 0.19, p = 0.59, I 2 : 0%, low certainty) and QUICKI (SMD 0.08, 95%CI -0.23, 0.38, p = 0.62, I 2 : 0%, low certainty), and cinnamon marginally improved HOMA-IR (SMD:-0.39, 95%CI -0.77, 0.00, p = 0.05, I 2 : 41%, low certainty). Flaxseed was investigated in three RCT, with two studies reporting a beneficial effect and one study reporting a neutral effect on IR in women with IR. Other herbal extracts and plant bioactive compounds, such as pomegranate, quercetin, spinach, fenugreek, crocin, fennel, green coffee, marjoram, propolis, Salvia officinalis , Sumac, and licorice were assessed in fewer studies, with mixed results. Conclusions Our findings suggest cinnamon may improve IR in PCOS, albeit with a low certainty of evidence. However, current evidence for other herbal extracts/compounds is not conclusive. Therefore, current evidence does not support the recommendation for the use of herbal extracts and bioactive plant compounds in the treatment of IR in PCOS. However, the shortcomings in our review highlight the need for further clinical trials to establish the clinical efficacy of herbal extracts and plant bioactive compounds for the treatment of IR in PCOS.