Eating a weekly portion of salmon could halve the risk of developing rheumatoid arthritis, researchers have found.

People who eat at least one serving of fatty fish, such as salmon, trout, mackerel or kippers, each week are said to be less likely to to develop the condition than those who do not.

The same benefit was observed in those who ate four servings of lean fish, such as cod, haddock or tinned tuna, each week.

The benefit is largely attributable to long-chain omega-3 polyunsaturated fatty acid (Pufa) content in fish, according to the study, published in the Annals of the Rheumatic Diseases.

Researchers collected dietary information on 32,000 women born between 1914 and 1948. The women completed lifestyle surveys, providing information about what food they ate, in 1987 and again in 1997.

During this time frame, 205 women developed rheumatoid arthritis.

After adjusting for various factors such as smoking habits, alcohol intake and age, the authors found women with consistently high daily intake in both 1987 and 1997 of more than 0.21g of omega-3 Pufas had a 52 per cent decreased risk in developing the condition.

The amount corresponds to at least one serving per week of fatty fish or four servings per week of lean fish, the researchers said.

They also noted that consistent long-term consumption of any fish once or more per week was associated with a 29 per cent decreased risk of developing rheumatoid arthritis.

Rheumatoid arthritis, thought to affect around 580,000 people across England and Wales, is a chronic inflammatory disease that causes pain and swelling in the joints.