People drinking too much coffee may increase the risk of developing rheumatoid arthritis, according to new medical research.Studies at the National Institute of Public Health in Finland, have found that people who drink 11 cups of coffee or more a day are almost 15 times as likely to have rheumatoid factor, which contributes to the onset of rheumatoid arthritis. The findings, published in the latest medical journal of Rheumatic Diseases, also show that those who have more than four cups a day are twice as likely to test positive for arthritis than those who drank less.But, more research has been called for as the ingredient in coffee that may increase the risk of developing rheumatoid factor has yet to be identified. According to the Coffee News Information Service, the study showed an association but not a cause and effect relationship. Coffee drinkers, it said, can be assured that coffee consumption in moderation is perfectly safe.The data was collected 20 years ago, when strong boiled coffee was the norm, so does not represent the normal UK consumption that is primarily of the instant variety, the Service added. Sarah Diston