The findings stem from a study of more than 32,000 Swedish women and offer another reason to follow the established dietary advice of regularly consuming fish for good health.
Researchers said the benefits of fishy diet are because it is rich in omega-3, which is said to protect both the heart and the brain.
A research team at Sweden's Karolinska Institute analysed the dietary habits of 32,000 women, all of whom were born between 1914 and 1948 and were followed from 2003 to 2010.
A total of 205 women were diagnosed with rheumatoid arthritis during the follow-up period and the researchers discovered that a high dietary intake of omega-3 fatty acids - which are found in fish such as salmon and fresh tuna - was associated with a reduced risk of the autoimmune disease.
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More than a quarter (27 per cent) of women who developed rheumatoid arthritis ate less than 0.21g of omega-3 fatty acids per day.
The findings suggest that women need to eat at least one portion of oily fish every week for several years in order to gain the most benefit.
"Fish body oil and fish liver oil are rich in omega-3 essential fatty acids, which can regulate the body's immune system and fight joint inflammation. We've known for some time that there is good evidence that in people with active arthritis, taking fish oils can reduce the level of inflammation," Professor Alan Silman, medical director of Arthritis Research UK, said.
The study was published in the journal Annals of the Rheumatic Diseases.