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Vitamin D Appears Beneficial In Reducing The Risk For Rheumatoid Arthritis

Greater intake of vitamin D, especially in the form of supplements, appears to be inversely associated with the incidence of rheumatoid arthritis (RA) in elderly women, say researchers.

Vitamin D has immunologic activity independent of its role in calcium regulation. In animal models, vitamin D has been demonstrated to suppress the development of autoimmunity, but its effects on the human immune system are not yet established.

Relatively little information is available regarding dietary or nutritional intake prior to RA onset, and the association of vitamin D with RA onset has not been previously assessed. To address this, Linda A. Merlino, MSc, College of Public Health, University of Iowa, Iowa City, United States, and colleagues. performed a study to evaluate the association of dietary and supplemental vitamin D intake with RA incidence.

The study population was an at-risk subset of participants enrolled in the Iowa Women's Health Study, a population-based prospective cohort study of 41,836 women who responded to a detailed self-administered questionnaire. Data regarding dietary variables and RA symptom onset for 29,368 subjects, aged 55 to 69 years, was collected for analysis.

A total of 152 cases of RA occurred during 11 years of follow up. Analysis showed that overall, greater intake of vitamin D was inversely associated with risk of RA (relative risk [RR] 0.67, 95% confidence interval [CI] 0.44-1.00, P for trend = .05).

Furthermore, inverse associations were observed for both dietary (RR 0.72, 95% CI 0.46-1.14, P for trend = 0.16) and supplemental (RR 0.66, 95% CI 0.43-1.00, P for trend = 0.03) forms of vitamin D.

Although no strong associations were found between RA risk and individual food items, an inverse association with RA risk was suggested for a composite measure of milk products (RR 0.66, 95% CI 0.42-1.01, P for trend = 0.06).

Interestingly, smoking appeared to contribute to RA risk. Relative to non-smokers, smokers with low vitamin D intake were at increased risk for RA (RR 1.8, 95% CI 1.16-2.75).

According to the researchers, the results of the study are largely hypothesis generating and will require further investigation.


Arthritis Rheum 2004 Jan;50:1:72-7. "Vitamin D intake is inversely associated with rheumatoid arthritis: Results from the Iowa Women's Health Study"

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