Effect of high-dose vitamin D supplementation on cardiometabolic risk factors in subjects with metabolic syndrome: a randomized controlled double-blind clinical trial.

PURPOSE: The evidence in support of the effect of vitamin D deficiency on cardiovascular diseases is inconsistent. The objective of this randomized, controlled, double-blind study was to assess the effect of high-dose vitamin D supplementation on cardiometabolic risk factors in subjects with metabolic syndrome. METHODS: Eighty subjects were randomized to receive 50,000 IU vitamin D or matching placebo weekly for 16 weeks. Fasting blood sugar, homeostasis model assessment of insulin resistance, insulin sensitivity (Quicki), serum lipid profiles (low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglyceride (TG) and total cholesterol), anthropometric factors and blood pressure were assessed before and after intervention. Dietary intake and sun exposure were also determined. The trial was registered at http://www.irct.ir (code: IRCT201409033140N14). RESULTS: Participants were 40.49 ± 5.04 years and 49 % male. All of the intervention group and 97 % of placebo group were vitamin D deficient or insufficient (25-hydroxyvitamin D <75 nmol/L). After intervention, serum 25(OH)D concentration was increased by 61.93 nmol/L in intervention group, while it was decreased in placebo group (p < 0.001). There was a significant change in TG concentration after 4 months (p < 0.001). Other metabolic or anthropometric factors did not change significantly (p = 0.05). CONCLUSION: Supplementation with high-dose vitamin D for 4 months improved vitamin D status and decreased TG levels in subjects with metabolic syndrome. However, it did not have any beneficial effects on other cardiometabolic risk factors; this might be due to the inadequate vitamin D status attained in this study which was conducted in a severely deficient region.

Daily intake of vitamin D- or calcium-vitamin D-fortified Persian yogurt drink (doogh) attenuates diabetes-induced oxidative stress: evidence for antioxidative properties of vitamin D.

BACKGROUND: Both poor vitamin D status and oxidative stress (OS) have been independently associated with late diabetic complications, including cardiovascular disease (CVD). The present study aimed to examine the effect of daily intake of vitamin D alone or in combination with calcium as a fortified Persian yogurt drink (doogh) on OS over 12 weeks. METHODS: Ninety patients with type 2 diabetes aged 30-50 years from both sexes were randomly allocated to one of the three groups to receive two 250-mL bottles of doogh a day, which was either plain (PD; containing 150 mg per 250 mL of calcium and no detectable vitamin D), vitamin D-fortified (DD; containing 150 mg of calcium + 500 IU vitamin D per 250 mL) or calcium-vitamin D-fortified (CDD; 250 mg od calcium + 500 IU vitamin D per 250 mL). RESULTS: Although mean (SD) serum concentrations of protein carbonyl significantly decreased in both DD and CDD groups [-2.07 (4.39) nm, P = 0.015 and -4.4 (7.64) nm, P = 0.003, respectively], the change in PD group was not significant [-0.54 (6.96) nm, P = 0.674]. A similar pattern was observed for cardiac myeloperoxidase [PD: -19.4 (75.9) µg L(-1) , P = 0.173; DD: -21.8 (54.2) µg L(-1) , P = 0.035, CDD: -48.5 (76.9) µg L(-1) , P = 0.002]. Superoxide dismutase increased significantly only in DD and CDD [56.9 (74.0) U L(-1) , P < 0.001 and 51.6 (119.9) U L(-1) , P = 0.025, respectively]. Changes of serum advanced glycation end-products showed a significant between-group difference among PD, DD and CDD [239.4 (388.4) U L(-1) , -58.1 (147.6) U L(-1) and -143.7 (475.9) U L(-1)  × 10(3) , respectively, P = 0.003], which remained significant after controlling for changes of fasting serum glucose (P = 0.013) and glycated haemoglobin (P = 0.015). CONCLUSIONS: The findings of the present study demonstrated an OS attenuating effect of vitamin D. However, extra calcium did not convey additional benefit.