Findings from a recent study indicated that consumption of vitamin D and omega-3 fatty acid supplements appear to diminish the risk of autoimmune diseases in older adults by 25% to 30% compared with those not taking these supplements.
At the recent 2021 American College of Rheumatology (ACR) Convergence Meeting, researchers presented findings from the first large, national, randomized, controlled trial examining the benefit of daily vitamin D supplements, omega-3 fatty acid supplements, or both supplements in preventing autoimmune disease. The presenters indicated that in observational studies, vitamin D has been inconsistently linked with reduced risk of several autoimmune diseases; however, a large randomized, controlled trial had not been conducted. They also noted that dietary marine–derived long-chain omega-3 (n-3) fatty acids decrease systemic inflammation and improve symptoms in some autoimmune diseases, but no trials have examined whether supplementation reduces the risk of developing autoimmune disease.
The Vitamin D and Omega-3 Trial was a nationwide randomized, double-blind, placebo-controlled study conducted in the United States that enrolled men who were at least age 50 years and women who were at least age 55 years or older in a two-by-two factorial design.
Women accounted for 51% of the cohort study, and the average age of participants was 67.1 years. The researchers divided the participants into four randomly assigned groups, each of which received a daily allotment for 5.3 years of either: 1) an n-3 placebo and a vitamin D placebo; 2) 1,000 mg of an n-3 fatty acid supplement and 2,000 international units (IU) of vitamin D; 3) an n-3 placebo and 2,000 IU of vitamin D; or 4) 1,000 mg of an n-3 fatty acid supplement and a vitamin D placebo. The trial was conducted from November 2011 to March 2014, and treatment continued until December 2017.
The researchers tested the effects of vitamin D3 and n-3 fatty acids on autoimmune disease incidence. Incident doctor-diagnosed autoimmune diseases were reported by participants annually and, if they existed, were confirmed via medical record review by expert physicians for classification criteria.
The primary endpoint was total incident autoimmune diseases, including rheumatoid arthritis, polymyalgia rheumatica, autoimmune thyroid disease, psoriasis, and all others. Prespecified secondary endpoints included common autoimmune diseases and probable autoimmune diseases (evidence of incident autoimmune disease but lacking enough medical record data to confirm). Results were displayed in cumulative incidence curves, and Cox regression models calculated hazard ratios (HR) of incident autoimmune diseases.
Of the 25,871 participants, 71% self-reported as non–Hispanic Whites, 20% African American, 9% other racial/ethnic groups, and 51% women. During median follow-up of 5.3 years, the researchers indicated that confirmed autoimmune disease was diagnosed in 117 participants in the vitamin D3 group and 150 in the placebo group (HR 0.78, 95% confidence interval 0.61-1.00, P = .04). The HR for vitamin D3 was 0.61 (0.43-0.86; 137 cases) excluding the first 2 years in prespecified analyses of the primary endpoint.
Confirmed autoimmune disease was diagnosed in 123 participants in the n-3 fatty acids group and in 144 participants in the placebo group (HR 0.85; 0.67-1.09). Excluding the first 2 years, the HR for the primary endpoint was 0.90 (0.64-1.26). When analyzed by factorial design subgroups, HRs for all three active arms versus placebo/placebo were reduced by 25% to 30%. The number needed to treat with both agents for 5 years to prevent one autoimmune disease was 167 (94-769).
The authors concluded that supplementation for 5 years with vitamin D3 and/or n-3 fatty acids diminished incident autoimmune disease by 25% to 30% in older adults versus those who received neither supplement. They also noted that the effect of vitamin D3 appeared stronger after 2 years of supplementation.
During a virtual presentation, Karen H. Costenbader, MD, MPH, of Brigham & Women's Hospital in Boston, Massachusetts, stated, "The clinical importance of these results is very high, given that these are nontoxic, well-tolerated supplements, and that there are no other known effective therapies to reduce the incidence of autoimmune diseases."
In a statement on the Medical News Today website, coauthor of the study, Professor JoAnn Manson, noted, "Both vitamin D and marine omega-3 fatty acids have immunomodulatory and anti-inflammatory properties. Thus, our finding that vitamin D supplements, either alone or in combination with the marine omega-3s, reduce the risk of developing autoimmune disorders is biologically plausible and warrants further study. The findings are exciting because no other preventive therapies are available to reduce the risk of developing these serious health conditions."
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