Vitamin D (the sunshine vitamin) is essential for good health. Human beings can make this hormone when skin is exposed to sunlight. In addition, vitamin D is found in a few foods: oily fish (and especially cod liver oil), fortified dairy foods, particularly milk, and mushrooms that have been exposed to UV light. Conditions such as cancer, asthma and ulcerative colitis have been associated with suboptimal levels of vitamin D in the bloodstream. Is there also a link between low vitamin D and rheumatoid arthritis?
Research Connecting Inadequate Vitamin D and Rheumatoid Arthritis:
Researchers from Spain report that lower levels of vitamin D in the body are in fact associated with more severe rheumatoid arthritis (70th AACC Annual Scientific Meeting & Clinical Lab Expo, July 31, 2018). They analyzed blood levels of 25-hydroxyvitamin D in 78 people with rheumatoid arthritis and 41 healthy individuals. Only about a third of the RA patients had adequate levels of the vitamin. Those with lower vitamin D levels had more painful joints.
Could Vitamin D Supplements Help?
Unfortunately, no one knows if supplements of vitamin D would help ease the symptoms of rheumatoid arthritis. Trials of vitamin D supplementation for other conditions have been disappointing. The importance of this vitamin to maintain bone integrity is well recognized. Even so, supplements have not proven helpful overall (Lancet, Jan. 11, 2014). A small daily dose in the context of a Mediterranean-style diet slowed bone loss in people with osteoporosis, however (American Journal of Clinical Nutrition, online July 11, 2018). That dose was 400 IU, also known as 10 micrograms per day.
When scientists do identify a benefit from supplements, it may be small. A meta-analysis of 81 randomized controlled trials found benefits for vitamin D supplements (Frontiers in Cardiovascular Medicine, July 12, 2018). While the effects on high blood pressure, cholesterol levels and C-reactive protein were positive, they were very modest.
Is There a Downside to Vitamin D Supplements?
Why don’t people with rheumatoid arthritis don’t just take vitamin D supplements and hope that it will help their joints? As with so many things, vitamin D supplements can have drawbacks, particularly at high doses. Research in mice suggests that high doses can shift fecal microbes into an inflammatory pattern (Scientific Reports, July 31, 2018). This would be an undesirable outcome. Another potential problem would be increased susceptibility to kidney stones (Nutrients, March 17, 2018). In summary, we should be sure that supplementation would truly offer benefit before recommending it as a potential therapeutic approach.
