A recent randomized, double-blinded, controlled study published in Journal of Clinical Rheumatology has found that supplementation with vitamin D2 has no effect on disease activity in rheumatoid arthritis. The researchers also found that vitamin D2 had a negative impact on symptoms.
Past epidemiological research on rheumatoid arthritis (RA) has shown that low vitamin D levels are associated with an increased risk of developing the autoimmune disease. There are also a few randomized controlled trials that have shown that increasing vitamin D levels decreases the severity of the disease. However, all of these RCTs used supplemental vitamin D3 as the intervention, not vitamin D2.