Cod liver oil can help arthritis sufferers
Researchers at Cardiff University have pinpointed unusual fatty acids, called Omega or n-3 fatty acids, as the crucial factor.
These fatty acids are present in fish oils but not other oils common in the diet.
Cartilage is the protective material that covers bones around the joints to stop them grating against each other.
Once incorporated into the cells, the fatty acids reduce the activity of enzymes that are responsible for damaging the cells and causing arthritis.
The fatty acids also cause the "switching off" of another recently-discovered enzyme that causes much of the pain and inflammation in arthritis.
This enzyme, Cyclooxygenase-2, is responsible for the biosynthesis of chemicals which cause inflammation.
Lead researcher Professor Bruce Caterson said: "This is a particularly interesting finding because there is intense activity in the pharmaceutical industry to find specific drug inhibitors of Cyclooxygenase-2."
Pain and inflammation
The fatty acids also switch off the long-term production of other chemicals known as inflammatory cytokines that prolong the pain and inflammation associated with arthritis.
Professor Caterson said: "These findings provide some very interesting explanations as to why granny's cod liver oil therapies have some benefits to arthritis sufferers.
"The good thing about modern day dietary supplements is that fish oil is available in capsules, thus preventing the most obvious deterrent to this treatment - the smell that precedes the terrible taste!"
Dr Madeline Devey, scientific secretary of the Arthritis Research Campaign, said the research was "terrifically exciting".
She said: "Taking fish oil is something that lots of people do because it makes them feel better, but we had had no idea why.
"Any good science that can be thrown at a common self-medication is a really good idea, and it might enable us to manipulate diet in a slightly more rational way than we do at the moment."