As we have reported often, studies suggest vitamin D has anti-inflammatory as well as immunomodulatory effects, implying a probable role in autoimmune disorders. Among the autoimmune diseases associated with vitamin D deficiency, the link has been particularly strong for Systemic lupus erythematosus (SLE). Dr Daniel Birmingham and colleagues found that large seasonal declines in vitamin D status may trigger SLE flare ups in non-African Americans (non-AAs).
Birmingham DJ, Hebert LA, Song H, Noonan WT, Rovin BH, Nagaraja HN, Yu CY. Evidence that abnormally large seasonal declines in vitamin D status may trigger SLE flare in non-African Americans. Lupus. Jan 2012.
The authors collected data from the Ohio SLE Study (OSS), a prospective study of 106 recurrently active SLE patients. To assess changes in vitamin D levels, 25(OH)D assays were performed for serum samples collected 4 and 2 months prior to flare and at the time of flare (-4, -2, 0), the authors call this 4 month period a “flare interval.” The authors tested 82 flare intervals from 46 patients.
The authors stratified the data by race and whether the flare occurred during a low daylight month (LDM – October through March) or high daylight month (HDM – April through September). They found:
- For non-AAs, median 25(OH)D levels at the time of LDM flare (19.7ng/mL) were significantly lower than levels at -2 months (27.7ng/mL) and -4 months(29.0ng/mL).
- Interestingly, there were no significant differences in 25(OH)D levels among AA participants during LDM months. The authors attribute this to overall lower levels among AAs and to insensitivity of seasonal effects, both due to UVB screening effects of pigmentation in skin.
Birmingham and colleagues also compared flare intervals and no-flare intervals in equivalent non-AA participants during corresponding LDM months. They found:
- The mean percentage decrease in 25(OH)D levels during flare intervals was significant (18.1%, p<0.001).
- The mean percentage decrease in 25(OH)D levels during no-flare intervals was not significant (6.2%, p=0.411).
- So, the decrease of 25(OH)D levels during flare intervals was about 3 times larger than the decrease during no-flare intervals.
The authors conclude:
“…The present work is consistent with the hypothesis that during LDM, a larger than usual decline in vitamin D status is a mechanism of SLE flare. The mechanism may involve a reduction in the roles played by vitamin D in modulating both the immune response and the inflammatory response.”
They state to further support their hypothesis future research requires a randomized controlled trial, controlling for skin color and seasonality. One such trial is currently under way. In the meantime, the Vitamin D Council believes that current research suggests it’s better to be sufficient than deficient.