Vitamin D supplementation may reduce autoimmune disease incidence, according to a study published in BMJ.
The study was part of VITAL (Vitamin D and Omega-3 trial), a five-year-long nationwide, randomized, double-blind, placebo-controlled trial, which included 25,871 participants. Participants were randomized into four groups: vitamin D treatment; vitamin D placebo; omega-3 treatment; or omega-3 placebo.
At the end of the study, a number of people were confirmed to have autoimmune diseases:
- Vitamin D treatment group: 123
- Vitamin D placebo group: 155
- Omega-3 treatment group: 130
- Omega-3 placebo group: 148
Statistical analysis found that those in the vitamin D treatment group (who received a dose of 2000 IU/day for five years), whether alone or in combination with 1 g/day of omega-3 fatty acids, had a statistically significant 22% reduction in incidence of autoimmune disease when compared to placebo. However, when only the last three years of the intervention were considered—after participants had already been supplementing for two years—the treatment group had 39% fewer participants with confirmed autoimmune disease.
In the omega-3 group, on the other hand, the reduction—15%—was not significant. However, when participants with probable autoimmune disease were included, supplementation did reduce the rate by 18% when compared with placebo, and a significant interaction was found with time, pointing to an increased effect after longer duration of supplementation.
The combination of vitamin D and omega-3 reduced incidence by 30%.
The study suggests some mechanisms of action: Vitamin D regulates several genes, many involved in inflammation and both innate and acquired immune responses, and indirectly inhibits T helper 17 cells, which play a role in the development of autoimmune disease. On the omega-3 side, animal and in vitro studies indicate that increased dietary intake of the fatty acids EPA and EHA inhibit inflammatory cytokines and decrease T cell proliferation and activation.
As to the implications, the researchers wrote: “This study… provides evidence that daily supplementation with 2000 IU/day vitamin D or a combination of vitamin D and omega 3 fatty acids for five years reduces autoimmune disease incidence, with more pronounced effects after two years of supplementation.” They added that they’re continuing to follow participants for two years in an extension study, in order to further test the reduction effect.
This study has more than just scientific value, according to Andrea Wong, Ph.D., SVP Scientific & Regulatory Affairs, Council for Responsible Nutrition. Dr. Wong told WholeFoods: “This is compelling research that has real-world implications for many Americans. The prevalence of autoimmune diseases is on the rise, and these diseases can cause serious tissue and organ damage. Since there are currently no cures, only treatment to reduce inflammation and symptoms, prevention is key. This study’s results show that supplementation with vitamin D and omega-3s can play an important role in reducing the incidence of these diseases.”