As many blog readers know, there has been much research studying the relationship between vitamin D and systemic erythematosus lupus of late. Some research shows that vitamin D and lupus have a relationship. But what does all the research say?
A new systematic review published recently in PLOS ONE examined this very question.
Sytemic lupus erythematosus, or often just called lupus, is an autoimmune disease characterized by chronic inflammation. The immune system attacks skin, joints, blood cells, and internal organs. Many patients develop a distinctive rash on the face that resembles a butterfly.
Various cells of the immune system express the vitamin D receptor, and multiple studies have found that lupus patients are more vitamin D deficient than the general population. However, sun exposure is a known cause of lupus flare-ups, so it has been proposed that sun-avoidance by lupus patients might actually be the cause of their low vitamin D levels.
In this review, the authors searched databases for studies that were observational in nature. They found 22 observational studies that examined the relationship between lupus and vitamin D. Eight were case-control and 14 were cohort type studies. They found the following:
- Out of the studies that looked at vitamin D levels and disease activity, 10 of the 15 studies found an inverse relationship between vitamin D levels and disease activity; the higher the vitamin D level, the lower the disease activity. Five of the fifteen studies did not find this relationship.
- In studies that examined disease damage and vitamin D levels, only 1 out 6 studies found an inverse relationship, while the other five found no relationship.
- In the four studies that investigated cardiovascular risk factors and vitamin D in lupus patients, the majority found that lower vitamin D levels were associated with more insulin resistance and unfavorable lipid profiles.
What does this mean for patients with lupus? The authors themselves say it best:
“…there is substantial evidence to convince us of the association between vitamin D levels and SLE disease activity.”
While acknowledging that some studies have not supported this relationship, they point out that the largest studies to date have confirmed the link between low vitamin D status and increased lupus disease activity.
However, the authors point out an interesting and unexpected finding of the research. The majority of studies found no relationship between vitamin D levels and organ damage from lupus disease activity. More disease activity usually translates to more damage to the organs. If higher vitamin D levels are associated with lower disease activity, why would there be no relationship between vitamin D levels and organ damage?
The cross-sectional nature of the majority of the studies reviewed makes it difficult to determine the long-term effects of vitamin D in lupus progression. Additionally, it may very well be that the true power of vitamin D lies in its power to prevent the conditions that allow an autoimmune disease to take hold. Once this process has started, vitamin D may not be as effective in treating the disease as it would have been in preventing it.
Also note that this systematic review only examined observational studies. The authors only wanted to examine the relationship between vitamin D and lupus, not if vitamin D had an effect as an intervention. The Vitamin D Council has previously blogged on a randomized controlled trial and an open label study, both designed to determine if vitamin D reduced flare-ups in people with lupus. Both studies found that supplementation with vitamin D did in fact reduce flare-ups:
- Vitamin D helps control lupus, says new randomized control trial
- Open study shows positive clinical results with vitamin D for patients with SLE
The authors in this present review state that “more trials are needed,” and we know there are a few already underway. For now, the use of vitamin D in lupus looks promising.