Effects of Vitamin D Supplementation on Cardiovascular and Glycemic Biomarkers

Background Experimental and observational studies have suggested a link between vitamin D and cardiovascular and metabolic disease, but this has not been confirmed in randomized controlled trials. We sought to determine whether vitamin D supplementation reduces biomarkers of insulin resistance, inflammation, neurohormonal activation, and lipids. Methods and Results This was a prespecified, secondary analysis of the DAYLIGHT (Vitamin D Therapy in Individuals at High Risk of Hypertension) randomized controlled trial. We measured circulating homeostatic model assessment of insulin resistance, hs‐CRP (high‐sensitivity C‐reactive protein), N‐terminal pro‐B‐type natriuretic peptide, renin, aldosterone, and lipids at baseline and at 6 months in 289 individuals with low vitamin D status (25‐hydroxyvitamin‐D [25‐OH‐D] ≤25 ng/mL) receiving low‐dose (400 IU/d) versus high‐dose (4000 IU/d) vitamin D3 for 6 months. A meta‐analysis of randomized controlled trials reporting biomarker changes after vitamin D supplementation was then performed. Levels of 25‐OH‐D increased in the high‐dose relative to the low‐dose vitamin D group (+15.5 versus +4.6 ng/mL, P P Conclusions In the DAYLIGHT randomized controlled trial, high‐dose vitamin D supplementation did not improve biomarkers of glycemia, inflammation, neurohormonal activation, or lipids. Registration URL: https://www.clinicaltrials.gov ; Unique identifier: NCT01240512.