Over the five-year study period, 123 of 12,927 participants in the vitamin D group (2,000 IU per day) were diagnosed with an autoimmune disease compared to 155 of 12,944 participants in the placebo group. This corresponds to a 22 percent lower relative risk. The longer vitamin D was taken, the clearer the difference was: If only the last three years of the study were considered, there were 39 percent fewer autoimmune diseases than in the placebo group.
The study also looked at omega-3 fatty acids: in the group that took them, 130 out of 12,933 participants were diagnosed with an autoimmune disease, compared to 148 out of 12,938 people in the placebo group. This corresponded to a reduction of 15 percent, which, however, did not reach statistical significance, so the effect could not be clearly demonstrated.
Autoimmune diseases occur when the body’s immune system mistakenly attacks healthy cells in the body. Common autoimmune diseases include rheumatoid arthritis, psoriasis and thyroid disease. Vitamin D and omega-3 fatty acids are known to have positive effects on inflammation and the immune system.
Even if the effects were small in absolute terms, the researchers consider the relevance of their results to be high, since there are no known effective therapies to prevent autoimmune diseases.
Which: DOI 10.1136/bmj-2021-066452