Slow down osteoarthritis

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Suggestions that diet may cause, cure, or alleviate arthritis have long been identified by the medical profession as quackery or unproved. Often the two words were used synonymously in pamphlets and other public education material to counteract the proliferation of diet and arthritis books sold at most health food stores. But in fact, little research attention had been devoted to a possible diet-arthritis connection.

Eventually, scientific evidence emerged indicating that about 5-10% of all cases of rheumatoid arthritis are due to food intolerance (Annals of Internal Medicine, April 1987). And now the most common form of arthritis, osteoarthritis, has been shown to respond to a certain type of diet. A new study found that a dietrich in vitamin D may slow the progression of osteoarthritis of the knee (Annals of Internal Medicine, 1 September 1996). The finding is significant because osteoarthritis is poorly understood and without effective treatment. It is a degenerative joint disease, which means that it progressively worsens with increasing wear and tear. Doctors do not know what causes the breakdown of cartilage that lines the joint and serves as a cushion, but it begins to thin, crack and flake as osteoarthritis develops, making movement painful. About 10% of all people over age 65 have osteoarthritis; many more have x-ray evidence of the disorder, but no symptoms.

The new study, conducted by Timothy E. McAlindon, D.M. and colleagues at several Boston-area medical centers, assessed the medical records and knee x-rays of 556 elderly people. Over the course of several years, the study participants had completed extensive questionnaires regarding their dietary habits, supplement use, and symptom severity. They were part of a much larger study known as the Framingham Heart Study which has followed the health habits and illnesses of people in one Massachusetts city for 40 years.

Of the participants whose knees showed x-ray evidence of osteoarthritis in the mid-1980s, those with diets and blood levels high in vitamin D were least likely to have further degeneration later in life. Most of these participants achieved high levels by taking supplements. Though the recommended daily allowance (RDA) of vitamin D is 200 international units, the best results were shown among people who were taking between two and eight times the RDA. Vitamin D is also manufactured by the skin when it is exposed to sunlight. Generally speaking, elderly people, especially those living in northern states, require supplements.

The new study found no evidence that people with a low intake of vitamin D were at greater risk of developing osteoarthritis; the benefit of high vitamin D intake was confined to halting progression in those who already had the disorder. Dr. McAlindon and colleagues speculate that vitamin D's contribution appears to be associated with its beneficial effect on the surrounding bone.

In an earlier study, Dr. McAlindon and colleagues found hints that a diet high in vitamin C had a similar effect of slowing the progression of osteoarthritis. But both the vitamin C and D studies are preliminary and therefore must be confirmed with further research.

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