Finnish researchers conducted two separate studies, both examining whether coffee had any association with the development of RA. In the larger study of more than 18,000 participants, researchers found that drinking 11 or more cups of coffee a day increased the risk for developing rheumatoid factor (RF), an antibody in the blood that doesn't necessarily cause RA but is believed to precede it by a few years. As many as 80 percent of the 2.1 million American patients suffering from RA test positive for this factor, convincing doctors there's a significant association between the two.
In the second study of almost 7,000 participants, researchers found that those consuming four or more cups of coffee per day were two times more likely to develop RA than those who drank less. Because there are many types of arthritis, it's important to note that this RA was the type whose onset was associated with positive tests for rheumatoid factor.
Does this mean that it's time to throw out the coffee mug? Not yet, suggest the authors of this paper. While the studies do show an association, they don't exactly prove that drinking large volumes of coffee is a guarantee for developing RA. There are several risk factors that doctors have traditionally used to assess a person's total risk for RA, and they include, smoking, obesity, high blood levels of cholesterol, increasing age and female gender. This study took those factors into account, and after doing so, still found that there was a doubling of the risk for those drinking four or more cups of coffee.
Now scientists and consumers are faced with a different question: What exactly is in the coffee that could be causing such problems? Caffeine immediately comes to mind, but is unlikely to be the culprit. No other study that has attempted to link environmental influences with the development of RA has shown that caffeine has any association at all. There are, however, several other chemicals in coffee that some studies have shown can be health-altering, including small compounds called diterpenes. More than one study has already shown that diterpenes can potentially increase the LDL (bad) cholesterol, so who's to say that it also doesn't predispose the body to RA?
The take-home message is caution rather than the need for drastic behavior change. It might be prudent to say that if you're predisposed to RA whether because you possess the other risk factors or because you have a genetic susceptibility it might be wise to cut back on the morning brew. So, until scientists can pinpoint the definite link, do your joints a favor and percolate with care.