The caffeine in coffee has been linked to cancer of the liver, bladder, kidney, and pancreas. But the research on the carcinogenicity of caffeine to support these claims was often anecdotal or fraught with inaccuracies and remains difficult to duplicate and validate.
Coffee is a complex chemical compound . Researchers , so far have identified more than three hundred substances in coffee, of which caffeine is but one. Caffeine is not the only substance in coffee that has been linked to bladder cancer. Tar and other chemicals formed when coffee is roasted have caused bladder cancer in guinea pigs even when no caffeine was present. One study reported from the Harvard School of Public Health showed that drinking two cups of coffee a day may double the risk of cancer of the pancreas. The researchers said the results were only preliminary and suggestive of further study.
To explore the other side of this issue, there are some studies lately that showed some evidence that caffeine may be anticarcinogenic and actually helpful in treating cancer. When caffeine is given in combination with radiation therapy or anticancer drugs, the effectiveness of these treatments seems to increase. Caffeine appears to prevent cancer cells from repairing themselves, hence making them more liable to destruction by radiation and drugs and less likely to spread quickly. But don’t jump the gun , caffeine is not a cancer cure. More research and work needs to be done in these area as well.
If, in the future, coffee consumption and the incidence of cancer are linked, chances are it will be due to another substance than caffeine found in coffee. These examples clearly show that definite evidence linking caffeine and the risk of cancer is still elusive and much more research is needed before an association can be made.