In some regions of the world, increased use of oral contraceptives may be associated with driving up rates of prostate cancer, according to a paper published this week in BMJ Open. Canadian researchers found a significant positive relationship between 2007 data on contraceptive use and global prostate cancer rates from the same year, with the strongest relationship showing up in Europe. No such relationship was found between prostate cancer and the use of other contraceptives, such as condoms and intrauterine devices.
The scientists suggested that hormones, especially estrogen, from the urine of people taking the pills may be leaching into the environment and contaminating drinking water or food supplies. Estrogen by-products are known to spur the growth of some tumors. But the Toronto University researchers, David Margel and Neil Fleshner, who authored the report, are quick to point out that their data reveal only an interesting correlation and not a causal link. Their study "must be considered hypothesis generating, and thought provoking," they wrote in the paper.
Some experts are still more dubious of the results. "Comparing the rates of two apparently unrelated issues across countries is a notoriously unreliable way of establishing whether they are truly linked," Cancer Research UK spokesperson Jessica Harris told BBC News. "So many things vary between different countries that it's impossible to say whether one thing is causing the other."