Vitamin D supplements and fish oil may help prevent autoimmune diseases, according to a study

Taking daily vitamin D and fish oil supplements may help protect older adults against developing autoimmune diseases such as rheumatoid arthritis, psoriasis, thyroid disease and polymyalgia rheumatica, an inflammatory disease that causes muscle pain and stiffness in the shoulders and hips, a new study shows.

People 50 and older who took 2,000 IU (International Units) of vitamin D3 for more than five years had a 22 percent lower relative rate of confirmed autoimmune diagnoses, said study author Dr. Karen Costenbader, a professor of medicine at Harvard Medical School in the division of Rheumatology, Inflammation and Immunity and director of the lupus program at Brigham and Women’s Hospital in Boston.

That’s two to three times the recommended daily allowance of vitamin D for adults, which is 600 IU for people up to age 69 and 800 IU for those 70 and older, according to the National Institutes of Health.

After people took vitamin D for at least two years, their rate of autoimmune disease prevention increased to 39 percent, according to the study published Wednesday in the journal BMJ.

The study also found a possible link between consuming 1,000 milligrams of omega-3 fatty acids (fish oil) and reducing autoimmune diseases, but the association was not statistically significant until possible cases of autoimmune diseases—not just confirmed ones—were taken into account in the analysis.

However, the study found that taking both vitamin D and omega-3 fatty acid supplements, compared to a placebo, reduced autoimmune diseases by about 30%. Costenbader cautioned that people should not rush to start taking vitamin D pills to increase their chances of avoiding autoimmune diseases, as there are significant consequences of taking too much of the supplement. Unlike water-soluble vitamins, which the body can easily eliminate, vitamin D accumulates in the body’s fat cells and can reach toxic levels, causing bone pain and kidney damage. Another study showed that a multivitamin intake substantially reduces brain aging.