Populations around the world with the most extensive use of the contraceptive pill also have the highest rates of prostate cancer, researchers from Toronto University have discovered.
Analysing data from many countries around the world, the researchers found an association between usage and rates of, and deaths from, the cancer, irrespective of a nation's wealth. The link was strongest in Europe.
They suspect that the pill's estrogen by-products - endocrine disruptive compounds (EDCs) - are making their way into the food chain and public water systems, and are causing the cancers.
EDCs 'feed' some cancers, and especially prostate tumours.
The researchers stress that an association is, at this initial stage, speculative, and has not yet been definitively proven.
(Source: British Medical Journal Open, 2011; 1: e000311).