Effects of Melissa officinalis (Lemon Balm) on cardio-metabolic outcomes: A systematic review and meta-analysis

Recent evidence indicates a beneficial effect of Melissa officinalis (MO) intake on several chronic diseases. However, the effects of MO intake have not yet been systematically reviewed. Therefore, we conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) to evaluate the effect of MO intake and focused on several cardiometabolic outcomes. MEDLINE, Scopus, EMBASE, Web of Science and the Cochrane Central Register of Controlled Trials were searched for MO-RCTs evaluating cardiometabolic outcomes. Random-effects meta-analyses estimated the pooled standardized mean differences (SMD) between intervention and control groups. Risk of bias was assessed with the Cochrane Collaboration's tool for assessing the risk of bias in RCTs. Seven RCTs were finally deemed eligible. MO intake was associated with a reduced total cholesterol (TC) (SMD: -0.26; 95% CI: -0.52, -0.01; I2 = 13.7%; k = 6) and a reduced systolic blood pressure (SBP) (SMD: -0.56; 95% CI: -0.85, -0.27; I2 = 00.0%; k = 3). MO intake was not associated with statistically significant changes in triglycerides, low-density lipoprotein, diastolic blood pressure, high sensitivity c-reactive protein levels, fasting blood sugar, HbA1c, insulin or high-density lipoprotein levels. No serious adverse events were reported. The risk of bias was high in a considerable amount of studies. Our study suggests that MO is a safe supplement with beneficial effects on TC and SBP. However, the findings of our study must be seen in the light of major limitations such as a low number of included studies and a serious risk of bias. High-quality RCTs are needed for firm conclusions concerning the effects of MO on cardiometabolic outcomes.