D May Protect Against Rheumatoid Arthritis
Women with highest levels of vitamin D intake are about one
third less likely to develop rheumatoid arthritis (RA)
than women with the lowest levels, findings from a new study
Although vitamin D is best known for its role in building bones,
it may also have effects on the immune system, senior author
Dr. Kenneth G. Saag, from the University of Alabama
at Birmingham, and colleagues report in the medical journal
Arthritis and Rheumatism.
To determine the effect of vitamin D intake on rheumatoid arthritis
risk, Saag's team analyzed data from nearly 30,000 women,
between 55 and 69 years of age, who participated in the Iowa
Women's Health Study. All of the women were rheumatoid arthritis-free
at study entry in 1986, and vitamin D intake was ascertained
through food frequency questionnaires.
During the 11-year follow-up period, 152 confirmed cases of
rheumatoid arthritis were identified, the investigators report.
Both dietary and supplemental vitamin
D intake were inversely linked with rheumatoid arthritis risk,
the authors found. High dietary (at least 290 IU/day) and supplemental
(at least 400 IU/day) intake were associated with 28
percent and 34 percent reductions, respectively, in the
risk of rheumatoid arthritis.
However, only the association between vitamin D supplement intake
and rheumatoid arthritis risk was statistically significant.
No single food item high in vitamin D or calcium was strongly
linked to rheumatoid arthritis risk, the researchers point out.
However, there was a trend toward a lower rheumatoid arthritis
risk with greater intake of milk products.
Although the effects of vitamin D on the immune system are not
yet fully defined, "the results from this study suggest
a possible role for vitamin D in reducing
the risk of an immunologic disorder," the authors
state. Further studies are needed to verify these findings,
SOURCE: Arthritis and Rheumatism, January 2004.