Extension data from the VITAL autoimmune disease prevention study reveals a new twist.
A two-year observational extension of the VITAL study has found that benefit of vitamin D supplements in preventing autoimmune disease dissipates after the pills are stopped.
On the other hand, data suggests the beneficial effect of omega-3 fatty acids continues after discontinuing the supplements.
“Strong rationale supports biologic effects of both vitamin D and marine n-3 fatty acids for autoimmune disease prevention and the results of the first five years of the VITAL supported the beneficial effects of both supplements for autoimmune disease prevention,” wrote the authors in Arthritis & Rheumatology.
“VITAL observational extension results suggest that vitamin D supplementation should be given on a continuous basis for long-term prevention of autoimmune disease.
“The beneficial effects of n-3 fatty acids, however, may be prolonged for at least two years after discontinuation.”
The original five-year study of over 25,000 people set out to discover whether omega-3 or vitamin D supplementation had any protective effects against cardiovascular disease or cancer.
Participants were men over 50 and women over 55 who weren’t deficient in either nutrient or known to be at risk for autoimmune diseases. They were randomised to one of four groups: 2000 IU daily vitamin D, 1g daily omega-3 fatty acids, both or neither.
There was no cardiovascular or cancer benefit. However, a sub-analysis found a statistically significant benefit of vitamin D in preventing autoimmune diseases, which included rheumatoid arthritis, polymyalgia rheumatica, psoriasis and psoriatic arthritis, autoimmune thyroid disease and inflammatory bowel disease. There was a similar trend for omega-3 supplementation that was statistically significant if “probable” (non-confirmed) cases were included.
For the observational extension study, more than 21,000 of the original participants (83.5%) agreed to take part. Researchers collected data on confirmed and probable incidence of autoimmune disease in the two years after the end of the randomised trial and looked at the protective effects of the supplements.
The hazard ratio for vitamin D was 0.98 (95% CI 0.83-1.17), suggesting the protective effect had dissipated over time. However, the benefit for omega-3 supplementation two years post-trial was statistically significant (HR 0.83; 95% CI 0.70-0.99).
More than one in four participants reported taking vitamin D supplements and almost one in four reported taking omega-3 supplements since the end of the trial proper. A reanalysis excluding those taking supplements didn’t change the results.
The authors also identified additional confirmed cases of autoimmune disease with a diagnosis during the original study timeframe. Reanalysing the results increased the hazard ratios for both vitamin D and omega 3s such that their protective effects were no longer statistically significant.
The authors pointed out that the doses selected were based on a balance of safety and potential efficacy for preventing cardiovascular disease and cancer, and suggested higher doses may have had more potent effect.
