Thursday, April 22, 2010

Rheumatoid Arthritis Due to Vitamin D Deficiency?

Vitamin DRecent commentary and research have suggested a link between vitamin D deficiency and the development or worsening of rheumatoid arthritis (RA). However, more and better research is needed to reach more definitive conclusions.

In addition to its traditional functions affecting bone metabolism, vitamin D has been shown to modulate the immune system and its deficiency has been associated with the development of several autoimmune disorders, including RA. Similarly, other disorders recently mentioned as being induced or influenced by deficient vitamin D have included type 1 diabetes, multiple sclerosis, systemic lupus erythematosus, Behcet’s disease (chronic vasculitis), polymyositis-dermatomyositis, and systemic scleroderma [Pelajo et al. 2010].

Further demonstrating a possible connection between vitamin D deficiency and RA, a new study found that women living in northern regions of the United States are more likely to develop RA. Writing in the journal Environmental Health Perspectives researchers found that women living in states like Vermont, New Hampshire, and southern Maine were more likely to report being diagnosed with RA. This was a large-scale longitudinal study examining data collected from nurses between 1988 and 2002, during which 461 women reported having RA compared with a large control group of 9,220 women. The researchers observed that, due to there being less sunlight in these areas, vitamin D deficiencies are common. "A geographic association with northern latitudes has also been observed for multiple sclerosis, Crohn's disease, and other autoimmune diseases that may be mediated by reduced vitamin D from decreased solar exposure and the immune effects of vitamin D deficiency," the researchers wrote.

Another recently-published study, in Rheumatology International, showed that serum vitamin D levels in persons with RA overall were similar to those in healthy individuals [Turhanoglu et al. 2010]. However, the levels of the vitamin were decreased significantly in accordance with a patient’s increasing disease activity and declining ability to function. Whether worsening RA status lowers vitamin D levels or, conversely, vitamin D deficiencies make RA worse was not determined.

CAVEATS: Associative data — ie, vitamin D deficiencies suspected or found in the presence of rheumatoid arthritis (RA) — do not demonstrate cause and effect. However, there does appear to be a link of some sort between this vitamin and immunological health, so it seems scientifically reasonable to presume there is a connection with RA. Prospective, controlled trials are needed to examine possible beneficial effects of vitamin D supplementation in persons with RA; however, to date, this line of investigation appears to have been neglected for unknown reasons.

> Pelajo CF, Lopez-Benitez JM, Miller LC. Vitamin D and autoimmune rheumatologic disorders. Autoimmunity Reviews. 2010 [February 8, epub ahead of print,
abstract here].
> Turhanoglu AD, Guler H, Yonden Z, Aslan F, Mansuroglu A, Ozer C. The relationship between vitamin D and disease activity and functional health status in rheumatoid arthritis. Rheumatol Int. 2010 [March 19, epub ahead of print,
abstract here]
> Vieira VM, Hart JE, Webster TF, et al. 2010. Association between Residences in U.S. Northern Latitudes and Rheumatoid Arthritis: A Spatial Analysis of the Nurses’ Health Study. Environ Health Perspect. 2010 [March 25, epub ahead of print,
article here].