Vitamin D May Protect Against Rheumatoid Arthritis

FRIDAY, Jan. 9, 2004 (HealthDayNews) -- Vitamin D may help protect against rheumatoid arthritis.

That's the conclusion of a new study in the January issue of Arthritis & Rheumatism.

Analyzing data from the Iowa Women's Health study, a large-scale research project begun in 1986, researchers looked at a sample of nearly 30,000 women, aged 55 to 69, who did not have rheumatoid arthritis at the study's start. The researchers followed the women for 11 years, asking them about eating habits, supplement use, smoking history and body mass index.

The greater the intake of vitamin D, the lower the risk of rheumatoid arthritis (RA), an autoimmune disorder involving inflammation in the lining of the joints and sometimes other internal organs as well. RA is often chronic and painful, and can flare up and then subside.

Rheumatoid arthritis affects 2.1 million Americans, mostly women, according to the Arthritis Foundation, and onset usually occurs in middle age.

In the study, the researchers discovered 152 cases of RA in the women during the 11 years of follow-up. And the study results suggest that getting enough vitamin D can reduce the risk.

"If they took in less than 200 international units (IUs) of vitamin D a day, they had roughly a 33 percent increased risk for developing rheumatoid arthritis compared with those who received more than 200 IUs daily," says senior investigator Dr. Kenneth G. Saag, an associate professor of medicine at the University of Alabama at Birmingham.

Four hundred international units of vitamin D a day are recommended, either from foods or supplements.

Exactly why vitamin D may guard against rheumatoid arthritis isn't known, Saag adds. "Vitamin D has its major effect in regulating calcium in the body," he says. "But we don't think this would necessarily explain this [protective effect] also."

"Vitamin D also has effects on the immune system," Saag adds, and it might somehow modulate the immune response that occurs when RA strikes.

Saag hopes further research will unlock the potential association between vitamin D and rheumatoid arthritis./p>

Meanwhile, he says, "this is just another reason why you need to eat a healthy diet."

It's best to get vitamin D from food, he says. "If you are getting enough in your diet, great. If not, you probably need to be supplemented." A cup of milk has about 100 IUs of vitamin D, and a cup of cornflakes about 40 IUs, according to the American Dietetic Association.

Dr. John Klippel is president and chief executive officer of the Arthritis Foundation, which helped fund the study. He calls the research results important. "Vitamin D appears to be protective," Klippel says, but "I think we need to be cautious in interpreting it" because the results are preliminary.

Klippel says the study is believed to be the first clinical research that has found a potential protective effect from vitamin D against rheumatoid arthritis.

Until more research is in, there are other ways to reduce the risk of RA, Klippel says. "Smoking appears to be a risk factor," he says. "Excess caffeine may be a risk factor."

Early detection of RA can help reduce pain, he adds. Joint pain and swelling of the hands, wrist and feet are often symptoms and should prompt medical attention, he says.

"The longer between diagnosis and treatment, the greater the risk of joint damage and disability," Klippel says. "See a rheumatologist early and get treated early."

More information

To learn more about rheumatoid arthritis or to assess your risk of arthritis, visit the Arthritis Foundation.