A meta-analysis of randomized controlled trials found vitamin D supplementation significantly improved a lupus biomarker and non-significantly reduced the recurrence of rheumatoid arthritis (RA).
Rheumatic conditions refer to conditions that affect the joints and muscles. Some of the conditions are caused by wear and tear; whereas, others occur as a result from problems with the immune system.
There are over 100 different types of rheumatic conditions. The most common types include osteoarthritis, RA, systemic lupus erythematosus (SLE), ankylosing spondylitis and Sjögren Syndrome.
Doctors often prescribe vitamin D for patients with rheumatic conditions in order to protect against glucocorticoid-induced osteoporosis. However, researchers believe that vitamin D may elicit a more profound effect on rheumatic conditions, one that is not yet recognized in the medical community.
Studies show that vitamin D plays a critical role in the immune system by regulating its activity. For instance, vitamin D inhibits two types of lymphocytes, Th17 and Th9, both of which are involved in the development of several autoimmune disorders.
Due to vitamin D’s well-established role in maintaining a healthy immune system, researchers recently hypothesized that vitamin D supplementation improves health outcomes in immune-mediated rheumatic diseases.
To test this hypothesis, researchers conducted a meta-analysis, a statistical procedure of compiling data from multiple studies. The analysis included a total of eight randomized controlled trials (the strongest study design) – five on RA and three on SLE.
The analysis aimed to determine the effects of vitamin D supplementation on pain, recurrence and disease activity in RA.
For SLE, the researchers wanted to know how vitamin D supplementation affected anti-dsDNA positivity. Anti-dsDNA is a test used to help diagnose SLE in a person who already has signs and symptoms of SLE. Anti-dsDNA refers to a group of antibodies that are created by a person’s immune system when it fails to distinguish between “self” and “nonself,” a characteristic trait of autoimmune conditions. About 50%-70% of people with lupus have positive anti-dsDNA results.
The researchers found the following
- After vitamin D supplementation, rheumatoid arthritis recurrence decreased. However, this was not quite statistically significant (P = 0.05).
- Anti-dsDNA positivity significantly decreased after vitamin D supplementation (P = 0.005).
- Neither pain nor disease activity scores in patients with RA significantly decreased after vitamin D supplementation (P = 0.24).
Why did vitamin D supplementation significantly help SLE patients but not RA patients? Differences in study designs may help explain this. In the three studies on SLE, all used vitamin D3 opposed to D2. Vitamin D3 has been shown to be more effective in increasing vitamin D levels than D2, and it is the predominate form found in nature, as D3 is from the sun. Furthermore, the majority (2/3) SLE studies used daily dosing opposed to bolus dosing, another design strength. One study used 2,000 IU daily, one study used both 2,000 IU and 4,000 IU daily and the third study used 50,000 IU weekly.
On the other hand, most RA studies (3/5) used weekly or monthly dosing. One of the five studies used vitamin D2 opposed to D3. One study used 500 IU of active vitamin D and one used .25 micrograms of alfacalcidol, a vitamin D analog, twice daily.
The researchers concluded,
“Vitamin D supplementation reduced anti-dsDNA positivity on systemic lupus erythematosus and could possibly reduce rheumatoid arthritis recurrence, although novel randomized clinical trials are needed to confirm and extend the benefits of this hormone in immune-mediated rheumatic diseases.”
Tovey, A. Cannell, J. Recent research investigates the role of vitamin D in rheumatic conditions. Vitamin D Council, June 20, 2017.