Effects of individual micronutrients on blood pressure in patients with type 2 diabetes: a systematic review and meta-analysis of randomized clinical trials

To investigate the effects of micronutrients on blood pressure (BP) in patients with type 2 diabetes through a systematic review and meta-analysis, randomized clinical trials (RCTs) of the effects of individual micronutrients on BP in patients with type 2 diabetes were searched in the Medline, Embase, Cochrane, and Clinical Trials.gov databases through April 2016. From the 28,164 studies, 11 RCTs (13 interventions, 723 patients, 54% males) with 3 to 52 weeks of follow-up were classified according to the type of micronutrient intervention: sodium (n = 1), vitamin C (n = 2), vitamin D (n = 7), and magnesium (n = 1). The available data enabled us to perform meta-analyses of vitamins C and D. Vitamin C reduced diastolic BP [WMD -2.88 mmHg (95%CI -5.31, -0.46; P = 0.020)] but not systolic BP [WMD -3.93 mmHg (95%CI -14.78, 6.92; P = 0.478)]. Vitamin D caused a reduction of 4.56 mmHg (WMD; 95%CI -7.65, -1.47; P = 0.004) for systolic BP and 2.44 mm Hg (WMD; 95%CI -3.49, -1.39; P < 0.001) for diastolic BP. In conclusion, vitamin D and possibly vitamin C have beneficial effects on BP in patients with type 2 diabetes. These interventions might represent a novel approach to the treatment of hypertension in these patients.