Drinking a lot of tea increases the risk of developing rheumatoid arthritis, researchers have said.

A US study on more than 76,000 women found consuming tea raised the risk, while drinking coffee had no impact.

Tea-lovers who enjoyed more than four cups a day had the highest risk - being 78% more likely to develop rheumatoid arthritis than those who drank none.

But drinking any amount of tea increased the chance by 40%, compared with people who never drank tea.

The findings were presented at the Annual Congress of the European League Against Rheumatism in Rome.

Professor Christopher Collins, from Georgetown University Medical Centre in the US, said he was surprised by the differences between coffee and tea.

He said: "We set out to determine whether tea or coffee consumption, or the method of preparation of the drinks was associated with an increased risk of (rheumatoid arthritis).

"It is surprising that we saw such differences in results between tea and coffee drinkers. This does make us wonder what it is in tea, or in the method of preparation of tea that causes the significant increase in risk of developing rheumatoid arthritis."

The researchers also examined whether filtered coffee versus unfiltered coffee affected the results, and also looked at the impact of caffeinated and decaffeinated coffee.

However, they found no significant associations with rheumatoid arthritis or the autoimmune disease systemic lupus erythematosus (SLE).