Patients with chronic heart failure are often deficient in vitamin D, which is associated with impaired prognosis. In the VINDICATE study, 229 patients with chronic heart failure and vitamin D deficiency were randomly allocated to 1 year of vitamin D3 supplementation (100 μg daily) or matching non-calcium-based placebo. The primary end point, 6-min walking distance, was not significantly different between the two groups. However, supplementation was associated with significant improvement in cardiac function (left ventricular ejection fraction +6.07%) and reversal of left ventricular remodelling (left ventricular end-diastolic diameter −2.49 mm, and left ventricular end-systolic diameter −2.09 mm). Whether these changes translate into improvements in clinical outcomes remains to be established. “Vitamin D might be a cheap and safe additional option for ... patients [with chronic heart failure],” conclude the researchers, “and may have beneficial effects on multiple features of the syndrome.”