Impact of short-term bilberry supplementation on glycemic control, cardiovascular disease risk factors, and antioxidant status in Chinese patients with type 2 diabetes

Bilberry (Vaccinium myrtillus L.) is one of the richest natural sources of anthocyanins which are powerful antioxidants and reported to have antiinflammatory, antidyslipidemic, antihypertensive, and hypoglycemic effects. The objective of this study was to assess the effect of bilberry supplementation on biomarkers of glycemic control, lipid profile, antioxidant, and inflammatory status in patients with type 2 diabetes in a randomized, double-blind, placebo-controlled cross-over study. Twenty patients were randomized to receive either bilberry supplementation (1.4 g/day of extract) daily for 4 weeks followed by 6 weeks of washout and then an additional 4 weeks of matching placebo or vice versa. Blood pressure, metabolic parameters, antioxidant status, and oxidative stress were measured before and after each period. Results showed no effect on body weight, blood pressure, or lipid profile. HbA1c was reduced by 0.31 +/- 0.58% during bilberry supplementation, but this change was not significantly different from that with placebo. Antioxidant status, oxidative stress, and inflammatory status showed no significant differences across treatments. This short-term study of bilberry supplementation did not show significant effects on cardiovascular risk factors or antioxidant status, but the tendency for improved glycemic control may suggest a longer treatment period may be effective in diabetic patients.