The type of fat you eat not only can affect your weight and heart, it may also determine the health of your joints. Eating too much unhealthy fat could worsen osteoarthritis.

Osteoarthritis is a disease of the joints that occurs when the top layer of cartilage wears away allowing the bones to rub together. Those who suffer with the disease have pain in their joints and reduced motion.

Overweight and obesity are primary risk factors for osteoarthritis, but it can be caused by many things. And while this explains why some joints wear out, it doesn’t explain why non-weight bearing joints, like those in the hands, are affected.

The omega-3 fatty acids didn’t reverse the injury, but appeared to slow down the progression of osteoarthritis.

Researchers at Duke University used mice with arthritis of the knee caused by injury to study the effect of different types of fat on the disease. One group of mice was fed a diet high in saturated fat. A second group ate a diet rich in omega-6 fatty acids, and a third group was fed a diet high in omega-6 fats, but supplemented with omega-3 fatty acids.

Mice that had omega-3 fatty acids added to their diets had healthier joints over the course of the study, while the osteoarthritic joints of the mice eating diets high in saturated fat or only omega-6 fats deteriorated. The study also found that arthritis was associated with the mice’s diet, but not with their weight.

The omega-3 fatty acids didn’t reverse the injury, but appeared to slow down the progression of osteoarthritis, according to Farshid Guilak, Ph.D., a professor of orthopedic surgery at Duke and the study’s senior author.

“Our results suggest that dietary factors play a more significant role than mechanical factors in the link between obesity and osteoarthritis,” Guilak said in a statement.

Omega-3's also seem to accelerate healing. Mice whose diets included omega-3 fatty acids healed more quickly from a small ear punch than mice who did not receive the supplemental fatty acid.

As with all animal studies, the findings must now be translated to humans. However, in the meantime those who suffer with osteoarthritis may find some relief from their symptoms by eating less saturated fat and omega-6 fats and eating more foods high in omega-3 fatty acids because of their anti-inflammatory properties. Ideally, we should eat pretty equal amounts of these fats, but the typical American diet is heavy in the saturated and omega-6 fats.

Fish and fish oil are the best sources of omega-3 fatty acids, but other good sources include flax seeds, canola oil, and walnuts. Some foods are fortified with omega-3’s as well. Saturated fats are found in animal foods like meat, cheese, whole milk, and butter. Omega-6 fatty acids are found in vegetable oils like corn and soybean oil, and in nuts and seeds.

The study was published in the Annals of the Rheumatic Diseases.