Two years after the end of a randomized trial that showed a benefit of daily vitamin D and omega-3 fatty acid (n-3 FA) supplementation for reducing risk for autoimmune diseases, the salubrious effects of daily vitamin D appear to have waned after the supplement was discontinued, while the protection from n-3 lived on for at least 2 additional years.
As previously reported, the randomized VITAL, which was designed primarily to study the effects of vitamin D and n-3 supplementation on incident cancer and cardiovascular disease, also showed that 5 years of vitamin D supplementation was associated with a 22% reduction in risk for confirmed autoimmune diseases, and 5 years of n-3 FA supplementation was associated with an 18% reduction in confirmed and probable incident autoimmune diseases.
Now, investigators Karen H. Costenbader, MD, MPH, of Brigham & Women’s Hospital in Boston, Massachusetts, and colleagues reported that among 21,592 participants in VITAL who agreed to be followed for an additional 2 years after discontinuation, the protection against autoimmune diseases from daily vitamin D (cholecalciferol; 2000 IU/d) was no longer statistically significant, but the benefits of daily marine n-3 FAs (1 g/d as a fish-oil capsule containing 460 mg of eicosapentaenoic acid and 380 mg of docosahexaenoic acid) remained significant.
“VITAL observational extension results suggest that vitamin D supplementation should be given on a continuous basis for long-term prevention of [autoimmune diseases]. The beneficial effects of n-3 fatty acids, however, may be prolonged for at least 2 years after discontinuation,” they wrote in an article published in Arthritis & Rheumatology.
Dr. Costenbader told this news organization that the results of the observational extension study suggest that the benefits of vitamin D “wear off more quickly, and it should be continued for a longer period of time or indefinitely, rather than only for 5 years.”
In addition to the disparity in the duration of the protective effect, the investigators also saw differences in the effects across different autoimmune diseases.
“The protective effect of vitamin D seemed strongest for psoriasis, while for omega-3 fatty acids, the protective effects were strongest for rheumatoid arthritis and inflammatory bowel disease,” she said.
Mixed Effects
In an interview with this news organization, Janet Funk, MD, MS, vice chair of research in the Department of Medicine and professor in the School of Nutritional Science and Wellness at the University of Arizona, Tucson, Arizona, who was not involved in the study, saidthat the results suggest that while each supplement may offer protection against autoimmune diseases, the effects are inconsistent and may not apply to all patients.
“I think the VITAL extension results suggest that either supplement (or both together) may have benefits in reducing risk of autoimmune diseases, including possible persistent effects posttreatment, but that these effects are nuanced (ie, only in normal weight post-vitamin D treatment) and possibly not uniform across all autoimmune diseases (including possible adverse effects for some — eg, inverse association between prior omega-3 and psoriasis and tendency for increased autoimmune thyroid disease for vitamin D), although the study was not powered sufficiently to draw disease-specific conclusions,” she said.
In an editorial accompanying the study, rheumatologist Joel M. Kremer, MD, of Albany Medical College and the Corrona Research Foundation in Delray Beach, Florida, wrote that “[T]he studies by Dr. Costenbader, et al. have shed new light on the possibility that dietary supplements of n-3 FA [fatty acid] may prevent the onset of [autoimmune disease]. The sustained benefits they describe for as long as 2 years after the supplements are discontinued are consistent with the chronicity of FA species in cellular plasma membranes where they serve as substrates for a diverse array of salient metabolic and inflammatory pathways.”