Supplements lower risk of rheumatoid arthritis and multiple sclerosis
13 January 2004
Helen R Pilcher
A diet rich in vitamin D may reduce the risk of developing rheumatoid arthritis and multiple sclerosis. Two studies involving more than 200,000 American women have highlighted the vitamin's benefits.
Women who consumed the recommended daily amount of vitamin D or more were 30% less likely to develop rheumatoid arthritis1, and 40% less likely to develop multiple sclerosis (MS)2, than those on lower doses.
One or two people in 100 worldwide typically develop rheumatoid arthritis, which causes swollen, painful joints. Around 0.04% of the world's population has MS - an incurable condition that can cause fatigue, tremor and paralysis.
Both conditions are thought to occur when the body's immune system turns against itself. Vitamin D may work by calming overactive immune cells, speculates Kenneth Saag from the University of Alabama, Birmingham, who led the arthritis study.
There is some animal evidence to support this idea. Mice with symptoms like those of multiple sclerosis or rheumatoid arthritis improve with vitamin D treatment. It will be interesting to see if the vitamin has the same therapeutic effect on human patients says Richard Keen from the Royal National Orthopaedic Hospital in Stanmore, Middlesex.
Bring me sunshine
Vitamin D is a steroid hormone that helps the body absorb and retain calcium. Too much can be toxic, while too little causes brittle bones.
The vitamin occurs naturally in some foods, such as liver and fatty fish, and is often added to others. One cup of fortified milk contains about half of the estimated adult daily need. But most of our vitamin D is home grown - the body makes it in response to sunshine. The daily dose can be achieved by soaking up bright sunshine on the face and hands for 15 minutes, three times a week - weather permitting.
The link with sunshine may explain why MS is more common in high latitudes, says Kassandra Munger of Harvard School of Public Health, Boston, Massachusetts, who contributed to the MS study. Those living a long way from the equator are exposed to less sunlight and may have suboptimal vitamin D levels - this may predispose some to developing MS.
Many people, particularly the elderly, are vitamin D deficient, adds Keen. This may explain why rheumatoid arthritis is more common in the elderly. "Supplements may offer good protection against this," he says.
"It's exciting to think that something as simple as taking a multivitamin could reduce your risk of developing MS," says Munger.
The arthritis study monitored the health of almost 30,000 women, and the MS study looked at more than 185,000 women. Subjects filled in questionnaires about their dietary habits and vitamin D intake at the beginning of each study, and were followed up every four years for up to 20 years.
Vitamin D expert Robert Heaney from Creighton University, Nebraska, cautions that this isn't the best way to estimate vitamin levels. Future studies should incorporate a blood test to assess vitamin D levels more accurately, he says.
Copyright © 2004, Nature News Service