Impact of oral vitamin D (cholecalciferol) replacement therapy on blood pressure in type 2 diabetes patients; a randomized, double-blind, placebo controlled clinical trial.

BACKGROUND: Vitamin D is an important mediator of calcium metabolism. It has also been implicated as a potential contributor to the pathophysiology of various extra-skeletal conditions, consisting hypertension, renal disease, and insulin resistance. OBJECTIVES: The primary objective of this study was to determine whether oral vitamin D (cholecalciferol) supplementation can lead to improvement of blood pressure in type 2 diabetes patients. PATIENTS AND METHODS: This study was a double blind clinical trial conducted on 60 type 2 diabetes mellitus patients. Exclusion criteria were taking calcium, vitamin D supplements or any drugs effecting calcium and vitamin D metabolism in the past 6 months. Patients were administered weekly vitamin D supplementation (50000 units) for 12 weeks. Serum 25-Hydroxy vitamin D [25(OH)D] level was measured with ELISA method. RESULTS: Five patients (8.3%) had vitamin D deficiency, 27 (45%) had insufficient levels of vitamin D and in 28 (45%) patients vitamin D level was within normal limits. The means of systolic blood pressure (BP) and diastolic BP in patients before intervention were 121 and 80.5 mmHg; after intervention they were 110 and 76.3 mmHg, respectively. After intervention, systolic and diastolic blood pressure levels were significantly less than control group (p< 0.01). CONCLUSIONS: In this study we found that weekly vitamin D supplementation (cholecalciferol; 50,000 units for 12 weeks) had beneficial effect on the level of blood pressure in type 2 diabetic patients. Thus, oral vitamin D may help in improvement of hypertension in these patients.