New data from a large placebo-controlled clinical trial investigating the effect of daily vitamin D and omega-3 use indicates the supplements may reduce the risk of developing autoimmune disease. At the five-year follow-up, the trial found those taking vitamin D alone, or in conjunction with omega-3, showed lower rates of autoimmune disease compared to those taking placebo.
Called VITAL, the ongoing trial has enrolled more than 25,000 participants who were randomly assigned to one of four groups: vitamin D and omega 3 (2,000 IU plus 1 gram of fish oil per day), vitamin D plus placebo, omega-3 plus placebo, or double placebo. At the time of recruitment the participants were aged over 50 and generally healthy.
The trial has been running for over five years now and several studies have already been published looking at the effect of these supplementations on cancer risk, cardiovascular risk and depression. For the most part, the trial has found little benefit to vitamin D and omega-3 supplementation in otherwise healthy subjects.
This latest analysis of the trial data looked at the emergence of newly diagnosed autoimmune diseases during the five-year trial. Autoimmune diseases in the trial included rheumatoid arthritis, polymyalgia rheumatica, autoimmune thyroid disease, psoriasis, and inflammatory bowel disease.
Overall, after five years, those taking either vitamin D alone or vitamin D alongside omega-3 displayed significantly lower rates of autoimmune disease compared to those in the placebo group. Little difference was seen in rates of autoimmune disease between the placebo group and those taking omega-3 alone, suggesting the benefits detected were primarily due to vitamin D supplementation.
Another important finding was the longer the trial went on, the lower the risk for autoimmune disease in the vitamin D group. Looking at the data from just the last three years of the trial saw 39 percent fewer cases of autoimmune disease in the vitamin D group compared to placebo. This suggests the greatest benefits of vitamin D supplementation in terms of autoimmune disease comes from a cumulative effect over several years.
“This is the first direct evidence we have that daily supplementation may reduce AD [autoimmune disease] incidence, and what looks like more pronounced effect after two years of supplementation for vitamin D,” said senior author Karen Costenbader.
“We look forward to honing and expanding our findings and encourage professional societies to consider these results and emerging data when developing future guidelines for the prevention of autoimmune diseases in midlife and older adults.”
This study is, of course, not without limitations. Despite the large number of trial participants and the robust protocol there was a relatively small volume of autoimmune disease diagnoses. Due to the slow onset of many autoimmune diseases a longer follow-up will be necessary to better understand the efficacy of these supplements as preventative tools.
The trial also solely focused on older healthy adults so there is no indication the results are transferable to younger populations or those already diagnosed with autoimmune disease. However, Costenbader is relatively comfortable recommending the vitamin D/omega-3 combination to those over the age of 50 looking for ways to reduce their risk of autoimmune disease.
“Now, when my patients, colleagues, or friends ask me which vitamins or supplements I’d recommend they take to reduce risk of autoimmune disease, I have new evidence-based recommendations for women age 55 years and older and men 50 years and older,” noted Costenbader. “I suggest vitamin D 2,000 IU a day and marine omega-3 fatty acids (fish oil), 1,000 mg a day – the doses used in VITAL.”
Another recently published study looking at vitamin D and overall mortality tracked more than 20,000 people taking either vitamin D or a placebo for several years. It found no difference in all-cause mortality or from cancer and cardiovascular disease when comparing the vitamin D group and placebo.