Vitamin D, fish oil supplements might reduce risk of autoimmune disease: Study

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Taking daily vitamin D supplements – or a combination of vitamin D and omega-3 fish oil – appears to carry a lower risk of developing autoimmune disease, with a more pronounced effect after two years, according to a recent study.</p>
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The study has been published in 'The BMJ Journal'. The researchers said 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."</p>
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Autoimmune disease happens when the body's natural defence system mistakenly attacks normal cells. Common conditions include rheumatoid arthritis, psoriasis, and thyroid diseases, which increase with age, particularly among women.</p>
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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 randomised trials have tested whether these supplements can lower the risk of autoimmune disease.</p>
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So 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 per cent women; 71 per cent non-Hispanic white).</p>
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When they joined the trial, 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.</p>
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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.</p>
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These included rheumatoid arthritis, polymyalgia rheumatica (pain and stiffness in the muscles around the shoulders, neck and hips), thyroid disease, and psoriasis, among others.</p>
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Reported cases were confirmed using medical records. Those with insufficient documentation for certainty were classed as "probable" cases.<br />
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 per cent lower relative rate.</p>
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In the omega-3 fatty acid group, 130 confirmed cases were diagnosed compared with 148 in the placebo group (a 15 per cent reduction), but this was not a statistically significant result.</p>
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However, when probable cases were included, omega-3 fatty acid supplements did significantly reduce the rate by 18 per cent compared with placebo and there was a significant interaction with time, indicating a stronger effect the longer supplements were taken.</p>
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Similar results were found when only the last three years of the trial were considered. The vitamin D group had 39 per cent fewer confirmed cases than placebo; while the omega-3 fatty acid group had 10 per cent fewer confirmed cases than placebo.</p>
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Both vitamin D and omega-3 fatty acid supplements decreased autoimmune disease by about 30 per cent versus placebo alone.</p>
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This was a large trial involving a diverse general population with high rates of follow-up and adherence to treatment. However, the researchers acknowledged that they tested only one dose and formulation of each supplement, and say the results may not apply to younger individuals.</p>
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Nevertheless, they said that this is the first direct evidence that daily supplementation with either agent – or a combination of vitamin D and omega-3 fatty acids – for five years among older US adults reduces autoimmune disease incidence, with more pronounced effect after two years of supplementation.</p>
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"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.<br />
"Further trials could test these interventions in younger populations, and those with high autoimmune disease risk," they added. </p>