Drinking milk may slow women's knee arthritis

The more milk women drank in a new U.S. study, the less deterioration they experienced in their arthritic knees.

It's not certain that milk was the reason for the slower arthritis progression, researchers said, and the effect was not seen in men. But the results add to evidence that nutrition may help to stave off arthritis.

"Milk is an excellent source of vitamins and minerals, dairy calcium and protein and has long been recognized for its important role in bone health," Dr. Bing Lu told Reuters Health in an email.

Lu, of Brigham and Women's Hospital in Boston, led the study, which was published in Arthritis Care and Research.

"We therefore hypothesized that milk consumption may prevent osteoarthritis progression," Lu said.

Arthritis causes pain and swelling of joints in the hand, hips or knees. According to the Centers for Disease Control and Prevention, it affects more than one third of Americans over age 65.

For the new study, Lu and colleagues analyzed data from a study launched in 2002 by the National Institutes of Health and focused specifically on osteoarthritis of the knee.

A total of 2,148 participants with 3,064 arthritic knees were involved in the analysis by Lu's team. They included 888 men and 1,260 women, who were all, on average, in their early 60s at the beginning of the study.

At that point, the participants answered questions about their diets, including how often they drank any kind of milk during the previous 12 months and how much they drank.

Because the space between bones in the knee narrows with deteriorating arthritis, X-rays were used to measure changes in joint space width in the affected knees. The researchers followed up with the participants at 12, 24, 36 and 48 months after the initial examinations and surveys.

Lu's team grouped the participants based on the number of eight-ounce glasses of milk they drank per week: none, fewer than three glasses, four to six glasses, and more than seven glasses.

When they compared the changes in joint space width among the participants over time, they found the width had decreased by 0.38mm in women who drank no milk at all, by 0.29mm in those who had up to six glasses of milk a week and by just 0.26mm in those who had more than seven glasses.

There was no such link between milk consumption and joint space width changes seen among the men.

"The gender differences in the relationship of milk consumption with osteoarthritis progression are not completely understood," Lu said, adding that sex differences have been noted in the prevalence, incidence and severity of arthritis for many years.

Previous studies have shown that the thickness of cartilage at the end of the distal femur, or thigh bone, is already smaller in women compared to men, Lu noted.