New York: US researchers have shown that shortage of a mineral is linked to knee arthritis.

Selenium, which occurs naturally in the soil and found in brazil nuts, shellfish, tuna, wholegrains and eggs, is believed to have anti-ageing properties and has been shown to protect men against prostate cancer.

The US study of 940 volunteers found that even tiny amounts of the mineral could protect against knee arthritis. For every additional tenth of a part per million of selenium in participants’ bodies, there was a 15% to 20% reduction in risk.

Those who had less of the mineral than normal in their systems faced a higher risk of osteoarthritis in one or both knees. The severity of disease was related to how low the selenium levels were.

Study leader Dr Joanne Jordan, of the University of North Carolina at Chapel Hill, said: “We are very excited about these findings because no one had ever measured body selenium in this way in relationship to osteoarthritis.

“Our results suggest that we might be able to prevent or delay osteoarthritis of the knees and possibly other joints in some people if they are not getting enough selenium. That’s important because the condition, which makes walking painful, is the leading cause of activity limitation among adults in developed countries.”

Volunteers were enrolled into the Johnston County Osteoarthritis Project, a continuing investigation of the disabling condition that was launched 15 years ago. It was the experience of people in severely selenium-deficient areas of China that led Dr Jordan to suspect that the mineral might play a role in preventing osteoarthritis.

In those regions, people frequently develop Kashin-Beck disease, which causes joint problems relatively early in life. Dr Jordan’s team compared the extent of knee osteoarthritis shown on X-rays with the amount of selenium in each volunteer’s body. Selenium was measured in toenail clippings taken from the participants. “We found that when we divided the participants into three groups, those with the highest selenium levels faced a 40% lower risk of knee osteoarthritis than those in the lowest-selenium group,” said Dr Jordan.