Impact of Vitamin D3 Versus Placebo on Cardiac Structure and Function: A Randomized Clinical Trial

BACKGROUND: Vitamin D supplementation leads to regression of left ventricular (LV) hypertrophy and improves LV function in animal models. However, limited data exist from prospective human studies. We examined whether vitamin D supplementa-tion improved cardiac structure and function in midlife/older individuals in a large randomized trial. METHODS AND RESULTS: The VITAL (Vitamin D and OmegA-3 Trial) was a nationwide double-blind, placebo-controlled randomized trial that tested the effects of vitamin D3 (2000 IU/d) and n−3 fatty acids (1 g/d) on cardiovascular and cancer risk in 25 871 individuals aged ≥50 years. We conducted a substudy of VITAL in which participants underwent echocardiography at baseline and 2 years. Images were interpreted by a blinded investigator at a central core laboratory. The primary end point was change in LV mass. Among 1054 Greater Boston– area participants attending in-clinic visits, we enrolled 1025 into this study. Seventy-nine percent returned for follow-up and had analyzable echocardiograms at both visits. At baseline, the median age was 64 years (interquartile range, 60– 69 years), 52% were men, and 43% had hypertension. After 2 years, the change in LV mass did not significantly differ between the vitamin D and placebo arms (median +1.4 g versus +2.6 g, respectively; P=0.32). Changes in systolic and diastolic LV function also did not differ significantly between arms. There were no significant changes in cardiac structure and function between the n−3 fatty acids and placebo arms. CONCLUSIONS: Among adults aged ≥50 years, neither vitamin D3 nor n−3 fatty acids supplementation had significant effects on cardiac structure and function after 2 years. REGISTRATION: URL: https://clinicaltrials.gov/; Unique identifiers: NCT01169259 (VITAL) and NCT01630213 (VITAL-Echo).