VITAMIN D AND MARINE N-3 FATTY ACID SUPPLEMENTATION AND PREVENTION OF AUTOIMMUNE DISEASE IN THE VITAL RANDOMIZED CONTROLLED TRIAL
Authors: J. Hahn et al.
In observational studies, vitamin D has been inconsistently associated with reduced risk of several autoimmune diseases, and a large randomized, controlled trial has been lacking. Dietary marine-derived long-chain omega-3 (n–3) fatty acids decrease systemic inflammation and ameliorate symptoms in some autoimmune diseases, but no trials have tested whether supplementation lowers risk of developing autoimmune disease.
A U.S. nationwide randomized, double-blind, placebo-controlled trial, enrolled 25,871 persons in a two-by-two factorial design. Randomization to vitamin D3 (2000 IU/d) and/or n-3 fatty acids (1000 mg/d) or placebo. Incident doctor-diagnosed autoimmune diseases were reported by participants annually and confirmed by medical record review. participants were randomized: During a median follow-up of 5.3 years, confirmed autoimmune disease was diagnosed in 117 participants in the vitamin D3 group and 150 in the placebo group (HR 0.78, p=0.04). Confirmed autoimmune disease was diagnosed in 123 participants in the n-3 fatty acids group and 144 in the placebo group (HR 0.85). When analyzed by factorial design subgroups, HRs for all three active arms vs. placebo/placebo were reduced by 25–30%. The number needed to treat with both agents for 5 years to prevent one autoimmune disease was 167.
This study suggests that dietary supplementation with vitamin D3 or n-3 fatty acids prevents incident autoimmune disease, but the high number to treat argues against the widespread implementation of this strategy in a population without particular risks.