Trial Finds Vitamin D, Fish Oil Supplements May Reduce Risk of Autoimmune Disease


The participants were asked to provide information on their age, ethnicity, region of residence, income, education, lifestyle, weight, medical history, diet, and supplement use.

Taking daily vitamin D supplements, or a combination of vitamin D and omega-3 fish oil, carries a lower risk of developing autoimmune disease and has a more pronounced effect after 2 years in older adults, according to a new trial published by the BMJ.

The research team noted that the clinical importance of these findings is high, “given that these are well-tolerated, non-toxic supplements, and that there are no other known effective therapies to reduce rates of autoimmune diseases.”

Both vitamin D and omega-3 fatty acids derived from seafood have been found to be beneficial for inflammation and immunity, but no large, randomized trials have tested whether these supplements can lower the risk of autoimmune disease, according to the study authors.

The research team tested the effects of vitamin D and omega-3 fish oil supplements on rates of autoimmune diseases in 25,871 US adults. The participants were asked to provide information on their age, ethnicity, region of residence, income, education, lifestyle, weight, medical history, diet, and supplement use.

Following this, the participants were randomized to receive vitamin D or matched placebo, and omega-3 fatty acids or matched placebo, and had to report any diagnosed autoimmune disease over an average 5.3 year period. These conditions include rheumatoid arthritis, polymyalgia rheumatica, thyroid disease, and psoriasis.

A confirmed autoimmune disease was diagnosed in 123 participants in the vitamin D group compared with 155 in the placebo group over the duration of the trial.

There were 130 confirmed diagnosed cases in the omega-3 fatty acid group compared with 148 in the placebo group, but this was not considered a statistically significant result. However, when probable cases were included, omega-3 fatty acid supplements did significantly reduce the rate by 18% compared with placebo, and a significant interaction was seen with time, according to the study.

The researchers noted that they only tested only 1 dose and formulation of each supplement and the results may not apply to younger individuals.

“We are continuing to follow participants for two years in an extension study to test the time course of this autoimmune disease reduction effect,” they wrote in a press release. “Further trials could test these interventions in younger populations, and those with high autoimmune disease risk.”


Vitamin D and fish oil supplements may reduce risk of autoimmune disease, trial finds. EurekAlert! January 26, 2022. Accessed January 28, 2022.

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