Study reveals surprising link between linoleic acid and occurrence of rheumatoid arthritis

Researchers have discovered that linoleic acid, a polyunsaturated fatty acid present in vegetable oils, may have a noticeable anti-inflammatory effect.

Omega 3 polyunsaturated fatty acids found in fish oils have long been linked with anti-inflammatory effects. A recent European study looking into diet and its impact on the development of rheumatoid arthritis revealed a surprising finding: linoleic acid, a polyunsaturated fatty acid present in vegetable oils, may have a noticeable anti-inflammatory effect.

Rheumatoid arthritis affects up to 1% of people globally. It is an auto-immune disease that causes swelling of joints resulting in disability if left untreated.

Research suggests that 60% of rheumatoid arthritis risk is down to environmental factors, but few such factors have been identified – smoking is the best example. Only 40% of rheumatoid arthritis risk is due to genetic factors.

Rich sources of Omega 3 polyunsaturated fatty acids are fatty fish and fish oils. A study in Sweden, based on a dietary questionnaire, showed that Omega 3 polyunsaturated fatty acids may protect against rheumatoid arthritis. But overall, studies have shown inconsistent findings on the impact of dietary intake of fish on arthritis prevention.

Scientists have, though, identified a potential ‘window of opportunity’ for protection during the earliest stage of the onset of rheumatoid arthritis. A recent controlled study aimed to investigate this further.

The study was based on a group of southern European participants whose lifestyle, including diet, has been monitored since the early 1990s as part of The European Prospective Investigation into Cancer and Nutrition (EPIC). Instead of using dietary questionnaires, the authors measured the proportions of different fatty acids in red cell membranes, as a more accurate indicator of a person’s fatty acid status.

The results of this study were surprising. They indicated that while there was no link in this population between intake of Omega 3 polyunsaturated fatty acids and a reduced instance of arthritis, higher levels of linoleic acid, an Omega 6 polyunsaturated fatty acid, were associated with a reduced occurrence of rheumatoid arthritis. Linoleic acid is found in polyunsaturated vegetable oils, such as sunflower, corn, soybean and cottonseed oil.

Dr Benjamin Fisher from the Institute of Inflammation and Ageing, who led the study, commented: "Our findings raise the exciting possibility that diet may alter the chances of developing rheumatoid arthritis developing.

"Although we have to be cautious and consider the possibility that low levels of linoleic acid might be an effect of unrecognised inflammation in the earliest phase of rheumatoid arthritis, rather than a contributing cause, samples were taken on average seven years before a diagnosis of rheumatoid arthritis was made.

"Furthermore, subsequent work by another group has lent support to our findings. More work is required so that in future we can give effective dietary advice to those who might be at risk."

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