Vitamin D and Omega-3 Could Reduce Autoimmune Disease Risk

Vitamin D has been inconsistently associated with reduced risk of several autoimmune diseases and large, randomized controlled trials have been lacking. Dietary marine-derived long-chain omega-3 fatty acids decrease systemic inflammation and ameliorate symptoms in some autoimmune diseases, but no trials have tested if they can lower the risk of developing autoimmune diseases.

New Controlled Trial 

In the most recent Convergence of the American College of Rheumatology 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.

The trial included men at least 50 years old and women at least 55 years of age, with a total of 25,871 participants. They were randomized into 2 groups, one taking vitamin D3 (2000 UI/d) and/or n-3-fatty acids (1000 mg/d) or placebo. The researchers tested effects of vitamin D3 and omega 3 fatty acids upon autoimmune disease incidence. 

During the 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. In the group taking omega-3 fatty acids 123 participants were diagnosed with autoimmune disease and 144 in the placebo group. 

They concluded that supplementation for 5 years with vitamin D3 and/or n-3 fatty acids reduced incident autoimmune disease by 25-30% in older adults vs those who received neither supplement and that the effect of vitamin D3 appeared stronger after 2 years of supplementation. 

The senior author of the study Dr. Karen Costenbader, director of the Lupus Program at Brigham and Women’s Hospital in Boston said: “In past ecologic observations, 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.” “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.”

She also added: “In past observational studies, lower RA risk has been observed in those with increased fatty fish intake.”

Co-author Prof. JoAnn Manson summed up the importance of the research for the medical news outlet for medical information, 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.”


Robby Berman (2021, Nov 18). Vitamin D and omega-3 supplements found to reduce autoimmune disease risk. Medical News Today. Retrieved from:

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