The vitamin D and omega-3 trial (VITAL) is a nationwide, randomized, double-blind, placebo-controlled trial with a two-by-two factorial design. The study consisted of 25,871 participants, 12,786 of which were men aged 50 or over, and 13,085 of which were women aged 55 or over.
A recent study published in the British Medical Journal (BMJ) found that supplementation with vitamin D and/or omega-3s may reduce the incidence of autoimmune disorders. The vitamin D and omega-3 trial (VITAL) is a nationwide, randomized, double-blind, placebo-controlled trial with a two-by-two factorial design. The study consisted of 25,871 participants, 12,786 of which were men aged 50 or over, and 13,085 of which were women aged 55 or over.
During the study, subjects were randomized to receive either 2000 IU/day of vitamin D or a matched placebo, and 1,000 mg/day of omega-3 fatty acids or a matched placebo. The primary endpoint was all incident autoimmune diseases that were then confirmed by a medical record review. Potential autoimmune diseases include: rheumatoid arthritis, polymyalgia rheumatica, autoimmune thyroid disease, psoriasis, and all others. Questionnaires were collected at baseline, and then after randomization, collected at six months, a year, and then annually for a median of 5.3 years of follow-up.
Results showed that in the vitamin D arm, 123 participants in the treatment group and 155 in the placebo group had confirmed autoimmune disease while in the omega-3 arm, 130 participants in the treatment group and 148 participants in the placebo group had confirmed autoimmune diseases. Cumulatively, the incidence of autoimmune disease was lower for the treatment group after five years than in the placebo group in both arms. In a preplanned analysis that excluded the first two years of follow-up in order to test the latency of treatment effects, researchers found that vitamin D group saw a significantly lower incidence of autoimmune disease (39%) compared to the placebo group. The omega-3 group, on the other hand, did not show statistically significant outcome.
In investigating the effects across four subgroups of the trial’s two-by-two factorial design, researchers found that the cumulative incidence of confirmed autoimmune disease was lower in all three groups receiving some form of supplementation: vitamin D and omega 3 fatty acid, vitamin D and omega 3 fatty acid placebo, vitamin D placebo and omega 3 fatty acid. This was not the case for participants taking two placebos. In a Cox model adjusted for age, sex, and race, with vitamin D placebo and omega-3 fatty acid placebo as the reference group, researchers determined that the incidence of autoimmune disease was lower for those randomized to receive vitamin D with omega-3 fatty acids, or without omega-3 fatty acids (22%), compared to receiving only placebo. If subjects were receiving omega-3 fatty acids alone, there was a marginally significant benefit.
The full study can be read here.