A weekly portion of fatty fish could halve your risk of developing rheumatoid arthritis.
The benefits of the fishy diet, however, depend on keeping up the diet for at least a decade.
They come from the omega 3 polyunsaturated fatty acid content known as PUFA.
If you don’t like fatty fish like salmon, four servings of lean fish like cod will have the same effect.
Researchers looked at the diets of more than 32,000 women born between 1914 and 1948 and tracked their health between 2003 and 2010.
Regular reports were given on their diets throughout the years including how often they ate fish and what type.
During the monitoring period 205 of the women were diagnosed with rheumatoid arthritis.
The researchers found across the entire group there was a fourfold difference in omega 3 PUFA consumption between those who eat the least and those who eat the most.
Among those who developed the condition, more than more than one in four (27pc) had a dietary omega 3 PUFA intake of less than 0.21g a day.
Those who eat more than that amount daily had half the risk (52pc) of rheumatoid arthritis.
And regularly eating one or more servings of all types of fish every week for at least 10 years was linked to an overall 29% reduced risk of developing rheumatoid arthritis compared with eating less than one portion a week.
The inverse association between fish consumption and rheumatoid arthritis can be attributed mainly to its content omega 3 PUFAs, the authors concluded.
They also said their findings indicated a potentially important role for these substances in the development of the disease.
The large study is published online in the Annals of the Rheumatic Diseases