A pill containing extracts of avocado and soybean oils – called avocado-soybean unsaponifiables (ASU) – may help prevent cartilage loss in people with hip osteoarthritis (OA). That’s the finding of a French clinical trial that was published recently in Annals of the Rheumatic Diseases.

In OA – which affects 27 million Americans – cartilage, which cushions the ends of bones, is damaged, causing pain, limiting function and leading to additional changes within the joint. Lifestyle changes, such as starting an exercise regimen, and certain medications can improve symptoms and slow the progress of the disease, but don't prevent the disease from getting worse.

The current study builds on nearly two decades of European research showing that ASU can improve arthritis pain and reduce the need for nonsteroidal anti-inflammatories (NSAIDs). One pilot study also suggested that ASU might preserve normal joint-space width in people with severe disease. Joint space, the area between the bones in a joint, narrows as cartilage wears away.

The latest finding is “significant,” says lead study author Emmanuel Maheu, MD, of St-Antoine Hospital in Paris, because it suggests that ASU might do more than improve symptoms, as the earlier studies showed. It might actually affect the course of the disease.

To determine whether ASU could preserve joint-space width in hip OA, Dr. Maheu and colleagues enrolled 399 patients from 122 French medical centers between 2000 and 2004. The majority of patients were women and most had experienced OA symptoms for about four years.

Participants were randomized into two groups. One group took a daily 300-milligram capsule of ASU. (The formulation was made of 1/3 avocado and 2/3 soybean extracts, manufactured by Laboratoires Expanscience. The brand is not available in the United States.). The other group took a placebo. Patients were allowed to take low doses of pain relievers and NSAIDs but had to keep track of their use.

Three different X-rays of the hip were taken for each patient at baseline and every year for three years – the duration of the study. Pain, disease severity and use of NSAIDs or pain relievers were also regularly assessed over the three-year period.

Final results showed no significant differences in joint-space width between patients taking ASU and those taking placebo. But when researchers looked how many patients had disease progression, those who took ASU fared much better. After one year of treatment, equal numbers of ASU and placebo patients were classified as “progressors,” meaning they had lost 0.5 millimeters or more of joint space. But by the third year, the difference between the two groups was statistically significant, with only 40 percent of the ASU group experiencing cartilage loss compared with 50 percent of the placebo group – a total of 20 percent fewer progressors among ASU patients.