Vitamin D and Autoimmune Disease: The VITAL Trial
The finding: Over five years, people taking 2,000 IU of vitamin D a day had 22% fewer confirmed autoimmune diagnoses than people taking a placebo.
What they did
VITAL was a nationwide American trial of 25,871 people: men aged 50 and over and women aged 55 and over, average age 67. It used a two-by-two design, so participants were randomly allocated to vitamin D (2,000 IU daily) or placebo, and separately to marine omega-3 (1,000 mg daily) or placebo. That let it test both nutrients, and their combination, in a single trial.
Participants were followed for a median of 5.3 years. Autoimmune diagnoses were self-reported first and then confirmed by going through the actual medical records, which matters more than it sounds, because self-reported illness is one of the main ways nutrition studies go wrong. The main conditions were rheumatoid arthritis, polymyalgia rheumatica, autoimmune thyroid disease and psoriasis. It was published in the BMJ.
What they found
- Vitamin D arm: 123 confirmed cases in the treatment group against 155 in the placebo group. Hazard ratio 0.78, 95% confidence interval 0.61 to 0.99. A 22% reduction.
- Omega-3 arm: 130 against 148. Hazard ratio 0.85, 95% confidence interval 0.67 to 1.08. A 15% reduction, which did not reach statistical significance on its own.
- Compared with the group taking neither, people taking vitamin D alone had a hazard ratio of 0.68, and people taking both had 0.69. Both combinations outperformed the group taking neither.
What this means for you
The dose was 2,000 IU a day, taken consistently for five years. Nothing exotic, and well within the range of an ordinary daily vitamin D supplement. Consistency over years is the part that is hard, not the dose.
What the trial does not tell you is whether vitamin D would help someone who already has an autoimmune condition. Everyone in VITAL started without one, so this is a study about incidence over time in older adults, not about treatment.
Worth saying plainly: nothing here is a reason to delay seeing a doctor about symptoms. Autoimmune conditions need proper diagnosis and proper care, and this trial does not change that.
The study
Hahn J, Cook NR, Alexander EK, et al. Vitamin D and marine omega 3 fatty acid supplementation and incident autoimmune disease: VITAL randomized controlled trial. BMJ. 2022 Jan 26;376:e066452.
General information only. This is a summary of published research, not a therapeutic claim and not medical advice. A result found in a trial population is not the same as a product doing that for you. Always read the label and follow the directions for use. If you have a health condition or take medication, check with your health practitioner before use.
