Both vitamin D and omega-3 fatty acids derived from seafood are known to have a beneficial effect on inflammation and immunity, but no large randomized trials have tested whether these supplements can lower the risk of autoimmune disease.
To find that, researchers set out to test the effects of vitamin D and omega-3 fish oil supplements on rates of autoimmune diseases in 25,871 US adults (average age 67; 51% women; 71% non-Hispanic white).
Participants provided information on their age, ethnicity, region of residence, income, education, lifestyle, weight, medical history, diet, and supplement use. Blood levels of vitamin D and omega-3 fatty acids were also measured.
Participants were then randomly allocated to receive vitamin D (2,000 IU/day) or matched placebo, and omega-3 fatty acids (1,000mg/day) or matched placebo, and were asked to report any diagnosed autoimmune disease over an average 5.3 year period.
These included rheumatoid arthritis, polymyalgia rheumatica (pain and stiffness in the muscles around the shoulders, neck, and hips), thyroid disease, and psoriasis, among others.
Reported cases were confirmed using medical records. Those with insufficient documentation for certainty were classed as “probable” cases.
Over the full duration of the trial, a confirmed autoimmune disease was diagnosed in 123 participants in the vitamin D group compared with 155 in the placebo group – a 22% lower relative rate.
In the omega-3 fatty acid group, 130 confirmed cases were diagnosed compared with 148 in the placebo group (a 15% reduction), but this was not a statistically significant result.
Similar results were found when only the last three years of the trial were considered. The vitamin D group had 39% fewer confirmed cases than placebo, while the omega-3 fatty acid group had 10% fewer confirmed cases than placebo.
This was a large trial involving a diverse general population with high rates of follow-up and adherence to treatment. However, the researchers acknowledge that they tested only one dose and formulation of each supplement, and say the results may not apply to younger individuals.
Source: Medindia
