The VITamin D and OmegA-3 TriaL (VITAL) is an ongoing randomized clinical trial in 25,871 U.S. men and women investigating whether taking daily dietary supplements of vitamin D3 (2000 IU) or omega-3 fatty acids (Omacor® fish oil, 1 gram) reduces the risk of developing cancer, heart disease, and stroke in people who do not have a prior history of these illnesses. The sponsor is Brigham and Women’s Hospital and collaborators include National Cancer Institute (NCI); National Heart, Lung, and Blood Institute (NHLBI); Office of Dietary Supplements (NCI) and National Center for Complementary and Integrative Health (NCCIH).
As reported in 2 Minute Medicine story, this randomized, placebo controlled trial enrolled healthy mature adult patients (men over 50, women over 55) between 2011 and 2014. Patients were factorially randomized to receive supplementation with a standardized dose of vitamin D (2000 IU per day), omega-3 fatty acid (840 mg per day, n=12933; n=12938 for patients receiving omega-3 placebo), both, or neither. Results of the study on outcomes associated with vitamin D supplementation are reported elsewhere. The primary endpoint of the study was a cardiovascular composite of myocardial infarction, stroke, or cardiovascular death. After a median of 5.3 years follow-up, this composite outcome occurred for 386 and 419 patients in the omega-3 and placebo groups, respectively (hazard ratio [HR], 0.92; 95% confidence interval [CI], 0.80 to 1.06; P=0.24). Of the secondary cardiovascular outcomes assessed, only the hazard ratio for myocardial infarction risk favored patients in the omega-3 group (0.72; 95% CI, 0.59 to 0.90), with 95% CIs of hazard ratios for death from cardiovascular causes, stroke, and expanded composite of cardiovascular events all crossing 1. Invasive cancer was diagnosed in 820 and 797 patients in the omega-3 and placebo groups, respectively (HR, 1.03; 95% CI, 0.93 to 1.13; P=0.56). Incidence curves for cancer diagnosis of all types appeared similar throughout follow-up. When analysis was performed in multiple subgroups there was no subgroup found to significantly benefit from omega-3 supplementation with regards to the composite cardiovascular risk outcome. There was no difference in serious adverse events or gastrointestinal symptoms between the placebo and omega-3 groups.