Vitamin D and Fish Oil Supplements May Reduce the Risk of Autoimmune Disease in Older Adults

Study authors say these findings are significant—but you should still talk to your doctor before starting (or changing) a vitamin regimen.

Vitamin D and Fish Oil Supplements May Reduce the Risk of Autoimmune Disease in Older Adults - A fresh fish is cut open to reveal its main asset: Omega Fatty Acids.
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A daily regimen of vitamin D and fish oil supplements may help prevent older adults from developing autoimmune diseases, like rheumatoid arthritis, thyroid diseases, and psoriasis, according to new research published in the BMJ.

Autoimmune diseases—conditions in which the body's immune system mistakenly attacks itself—are very common, and their chances of developing increase with age. Though all autoimmune diseases vary to some degree, they mostly develop gradually—usually over the course of months to years.

For this specific study, researchers set out to answer whether vitamin D and marine-derived long-chain fatty acids (aka fish oil)—known for their ability to regulate the immune system and tamp down inflammation—may also have a protective effect against autoimmune disorders. As it turns out, they might.

"There are no other treatments or preventative therapies available for autoimmune disorders," JoAnn Manson, MPH, co-author of the study and chief of preventative medicine at Brigham and Women's Hospital, tells Health, explaining that autoimmune conditions are prevalent and have major affects on health and quality of life. "These supplements may be able to reduce morbidity related to autoimmune disorders," she adds.

Here, we help explain what this new research means for you—and what, if any, precautions you should take before running out to buy vitamin D and fish oil supplements.

Vitamin D and Fish Oil Effects on Autoimmune Diseases

In a corresponding BMJ opinion piece to the study, co-author Karen Costenbader, MD, MPH, revealed that she and her colleagues set out to answer this one question, posed to doctors by patients: "Which vitamins or supplements do you recommend that I take?"

According to Dr. Costenbader, the lupus program director at Brigham and Women's Hospital's division of rheumatology, she can now point to this research, which suggests women over 55 and men over 50 take 1,000 mg of marine omega-3 fatty acids (fish oil) and 2,000 IU of vitamin D each day, to reduce the risk of autoimmune diseases.

For the study, researchers analyzed data from 25,871 men and women, over 50 and 55 years old, respectively. They were participating in VITAL, a nationwide, randomized, double-blind, placebo-controlled trial designed to see whether vitamin D and fish oil supplementation could help prevent cancer and cardiovascular disease. The participants were split up into four groups—those who took 2000 IU/day of vitamin D, those who took 1000 mg/day of fish oil, and those who took placebo doses of vitamin D and fish oil—and were followed for about five years. They were also asked to report any new diagnoses, side effects, and trial adherence on a yearly basis.

Though VITAL showed no benefits to cancer or cardiovascular disease prevention, researchers chose to use the same data to investigate the supplements' effects on autoimmune diseases—that's where they found the most benefit.

In all, researchers determined that participants who received vitamin D supplementation with or without fish oil were 22% less likely to develop an autoimmune disease. Those who received fish oil supplementation with or without vitamin D saw a 15% reduction in autoimmune disease rate—though that was deemed "not statistically significant" to researchers, compared to placebo.

"We found that the participants who took the two pills that were a placebo had the highest risk of autoimmune disease," Dr. Costenbader tells Health. "I was very excited about the results that we finally had. This is the first thing we know that we can do to prevent autoimmune disease, a proven therapy."

Though the study followed participants for just over five years, Dr. Manson says even the effects that emerged after just two years of supplementation were significant. "Often the effects of these supplements can take a long time to emerge. The fact that this benefit was apparent within two years—there seemed to already be a reduction that was emerging—and then it was statistically significant over five years for vitamin D either alone or combined with omega-3s was surprising."

While the study findings were significant, more research is still needed to address further questions regarding vitamin D and fish oil supplementation and their effect on autoimmune disease—particularly whether the preventive effects will be long-lasting, and if they can be replicated in younger generations. "We have a strong interest in looking at younger adults because auto-immune diseases often manifest in the early adult side," Manson said. "A repeat study looking at younger adults and targeting those who have risk factors for immune disorder and a strong family history would be very helpful in seeing if the findings can be replicated."

Should You Start Taking Vitamin D and Fish Oil

Though vitamins and supplements are generally regarded as safe, it's still possible to take too much—which means your doctor should be clued into any new ones you want to try (or even if you want to up your dosage).

This study in particular gave participants 2,000 IU/day of vitamin D—that dosage is kind of in between the daily recommended dosage for adults (600–800 IU) and the upper limit for adults (4,000 IU), according to the National Institutes of Health's Office of Dietary Supplements. Manson points out that the NIH daily recommendations are primarily for bone health. "They don't have recommendations on preventing other chronic diseases such as cancer or cardiovascular disease or recommendations for preventing autoimmune disease," she said. "We tested these supplements over 5.3 years and found they were very safe."

Still, you can overdo it on vitamin D. "People should keep in mind that taking too much vitamin D can possibly cause toxicity so it would not be recommended to take higher than 2000 IU daily on a regular basis," Ozlem Pala, MD, a rheumatologist at the University of Miami Health System, tells Health. In excess, vitamin D can cause nausea and vomiting, muscle weakness, and kidney stones, among other issues; very high levels in the blood can lead to kidney failure or even death. It can also interact with certain medications, like statins and steroids.

Regarding fish oil—the study dose of which was 1,000 mg/day—the NIH sets the daily recommended dosage for omega-3s as 1,100 mg/day to 1,600 mg/day for adult women and men, respectively. The Food and Drug Administration says dietary supplements providing up to 5 g/day (5,000 mg/day) of EPA and DHA (the types of omega-3s in fish oil) are considered safe. Though omega-3s usually only have mild side effects, if any, supplementation could interact with anticoagulants or blood thinners.

Overall, any new vitamins should be discussed with your health care provider, says Dr. Costenbader. "I think anybody who wants to start taking any over-the-counter supplements will hopefully talk to their doctor about it and make sure it doesn't interact with their other medications or other health problems."

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