Autoimmune disease: Vitamin D and omega-3 supplements may reduce risk

• Previous research has noted correlations between vitamin D, omega-3 fatty acids, and autoimmune disease.
• According to the authors of a new study, there has been no large scale, randomized controlled trial to investigate the possible connections.
• The new, long-term clinical study has now found that vitamin D, omega-3 fatty acids, or both reduce the risk of developing an autoimmune disease.

Previous research has identified a correlation between vitamin D consumption and a reduced incidence of autoimmune diseases. The same is true of marine-derived omega-3 fatty acid supplements.

Now, at the American College of Rheumatology’s ACR Convergence 2021, researchers have presented the results of the first large, national, randomized controlled trial investigating the value of daily vitamin D, omega-3 fatty acid, or both supplements in preventing autoimmune disease.

In the trial, taking vitamin D and omega-3 fatty acid supplements for 5 years reduced the occurrence of autoimmune disease in older adults by 25–30%, compared with not taking them.

Preliminary clues

Senior author of the research Dr. Karen Costenbader, director of the Lupus Program at Brigham and Women’s Hospital in Boston, recapped for the conference attendees the earlier studies that led to the new trials.

When the human body gets exposure to sunlight, it produces vitamin D, which supports healthy teeth and bones. With less sunlight, the body may not generate enough vitamin D naturally. Research has linked insufficiency of vitamin D to a range of conditions.

“In past ecologic observations,” Dr. Costenbader explained to the conference audience, “inflammatory bowel disease, multiple sclerosis, and type 2 diabetes have been shown to be more prevalent at northern latitudes, where circulating vitamin D levels are lower.”

Conversely, she added, “Both high plasma 25-OH vitamin D and high residential UV exposure were associated with a decreased risk for rheumatoid arthritis [RA] among women in the Nurses’ Health Study in our past work.”

Of omega-3 fatty acids, Dr. Costenbader said, “In past observational studies, lower RA risk has been observed in those with increased fatty fish intake.”

Dr. Costenbader also noted that in a different study, “higher [omega-3 (n-3)] fatty acid-to-total lipid proportion in [red blood cell] membranes was associated with a lower prevalence of anti-CCP and rheumatoid factor antibodies, and lower progression to inflammatory arthritis among healthy volunteers.”

The VITAL trial

Dr. Costenbader and her colleagues recruited 25,871 adults for the VITamin D and OmegA-3 TriaL (VITAL).

All of the men who participated were aged 50 years or older. The women, who accounted for 51% of the cohort, were aged 55 years or older. The average age of the participants was 67 years.

The researchers divided the participants into four randomly assigned groups, each of which received a daily allotment for 5.3 years of either:

• an omega-3 placebo and a vitamin D placebo
• 1 milligram (mg) of an omega-3 fatty acid supplement and 2,000 international units (IU) of vitamin D
• an omega-3 placebo and 2,000 IU of vitamin D
• 1 mg of an omega-3 fatty acid supplement and a vitamin D placebo

The trial ran from November 2011 to March 2014, and treatment continued until December 2017. The participants reported physician-diagnosed autoimmune issues as they arose.

A reduction in risk

The researchers assessed the effect of vitamin D and omega-3 fatty acids on autoimmune disease overall and on individual autoimmune conditions.

In the final analysis, the incidence of autoimmune disease was reduced by 25–30% for participants who took vitamin D supplements, omega-3 fatty acid supplements, or both, compared with people who took only placebos.

“The effect of vitamin D3 appeared stronger after 2 years of supplementation,” write the researchers.

“The reduced incidence of RA and polymyalgia rheumatica are very important for rheumatology,” says Dr. Costenbader. “The more pronounced effect after 2–3 years of use with vitamin D makes sense biologically and supports long-term use.”

Co-author Prof. JoAnn Manson summed up the importance of the research for Medical News Today:

“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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