Herbal antioxidants as tertiary prevention against cardiovascular complications in type 2 diabetes mellitus: A systematic review

The prevalence of diabetes and its cardiovascular complications is increasing globally. Some patients practice supplementation with herbal antioxidants, although limited evidence justifies their intake. Thus, the present review was aimed at investigating the effect of herbal antioxidants preventing coronary heart disease as a complication of type 2 diabetes mellitus. PubMed, Emerald Insight and Web of Science databases were comprehensively searched to retrieve published literature on the use of herbal antioxidants as preventive therapies against cardiovascular complications of diabetes. The review was limited to clinical trial studies, publications within the last 5 years and English texts. The outcomes measured were the effect of herbal antioxidants on the blood and physical parameters commonly associated with the risk of developing coronary heart disease. Twelve randomised controlled trials comparing herbal antioxidant supplementation and placebo control (overall, n = 771) met the inclusion criteria. No single antioxidant was entirely effective for improving the whole set of cardiovascular parameters. Lemon balm was associated with significant changes in high-density lipoprotein cholesterol, triglycerides, and systolic blood pressure (BP), as well as high-sensitivity C-reactive protein (hs-CRP). Significant changes in body weight, body mass index and hs-CRP were shown with curcumin. Saffron had a significant effect in lowering systolic BP. The heterogeneity of the results limits the conclusive evidence for herbal antioxidant supplementation. However, herbal antioxidant intake may contribute some benefits to certain parameters that usually increase the risk of heart disease.