By Steve Weakley

Does what’s in your gut influence the pain in your knees? New research on mice at the University of Rochester Medical School suggests that it might, but the results are far from conclusive.

Researchers fed one group of laboratory mice a high fat diet that included red meat and milkshakes, and another group of mice a healthier low-fat diet. Both groups of mice had their knees surgically damaged to mimic the effects of osteoarthritis -- “wear and tear” arthritis that is often associated with age, obesity or injury.

Twelve weeks of the high fat diet made the mice obese and diabetic and led to more seriously damaged joints. It also created an imbalance of harmful bacteria in their digestive tracts. 

One group of the fat mice were then given a supplement containing the prebiotic fiber oligofructose (also available as an over-the-counter probiotic).  The researchers said the supplement did not cause the mice to lose weight, but it did greatly improve their blood sugar levels and the balance of healthy bacteria in their gut.  More importantly, the study concludes, the mice that were given the supplement also had healthier joints than the control group.

The University of Rochester study concluded that prebiotics and the correction of gut bacteria might help protect against osteoarthritis caused by obesity. And one of the researchers, Dr. Robert Mooney, told Forbes that the study suggests osteoarthritis may be accelerated or even caused by inflammation.

"That reinforces the idea that osteoarthritis is another secondary complication of obesity--just like diabetes, heart disease, and stroke, which all have inflammation as part of their cause," said Mooney. "Perhaps, they all share a similar root, and the microbiome (digestive bacteria) might be that common root."

However a critique by Britain’s National Health Service (NHS) said that conclusion might be premature.

“It's presumptuous to conclude that an imbalance of gut bacteria could be directly linked to risk of osteoarthritis in humans from the results of a study in mice with artificially induced knee damage. As such, there's no compelling evidence that prebiotics would prevent or reverse osteoarthritis,” the NHS said.

“Aiming for a healthy weight through a good diet combined with physical activity is a better strategy for reducing the risk of osteoarthritis (as well as many other long-term conditions) than taking prebiotics to try to combat the effects of a poor diet. “

Osteoarthritis is a joint disorder that leads to progressive joint damage. It can affect any joint in the body but is most commonly felt in weight bearing joints such as the knees and hips. Nearly 40 percent of Americans over the age of 45 have some degree of knee osteoarthritis.

Previous studies have also found a link between a high fat diet and osteoarthritis.  Australian researchers reported last year that a diet rich in animal fats, butter and palm oil weakens cartilage and produces osteoarthritis-like changes in the knee.

"We also found changes in the bone under the cartilage on a diet rich in saturated fat," said Professor Yin Xiao of Queensland University of Technology’s Institute of Health and Biomedical Innovation. "Our findings suggest that it's not wear and tear but diet that has a lot to do with the onset of osteoarthritis.”

The University of Rochester researchers hope to include humans in future studies on the effects of diet on osteoarthritis.