There's been an outbreak of news stories about cancer risk from over-cooked starchy foods because of the production of substances called acrylamides. If your roasties, chips and toast, for instance, are too dark, we are told that they could increase your risk of cancer. This is not news - it's an idea that has been around for a long time and was covered in Science for Life. All that's new is that the Foods Standards Agency (FSA) has launched a campaign called Go for Gold encouraging us not to cook these starchy products too harshly and to leave them golden coloured. Bizarrely they are using that well known food science expert, Olympic medallist Denise Lewis to publicise the campaign (see what they've done - go for gold?), and the FSA wants us to cut back.
As mentioned in Science for Life, some studies do show a small potential increased risk of a handful of cancers, so there's no harm in avoiding really dark fried or grilled starchy foods, which is what I recommended. However, these studies are not definitive - in fact at the moment the general view is that there is no strong evidence of risk from acrylamides - and even if the risk does exist, it is small enough to happily still enjoy the crunchy bits of roast potatoes.
To put it into context, lots of things we eat may well produce a very small increase in risk of cancer. Things like, for instance, those killer foods orange juice and celery. We know for certain that alcohol has the biggest influence on cancer risk of anything we eat or drink, and coffee certainly has some small risk attached. But it the grand scheme of things, worrying about these small risks is like worrying about being struck by lightning or being in a fatal train crash. It can happen. It will happen to some people. And you don't want to stand on a high hill holding a metal pole in the air when there's thunder nearby. But life's too short to worry excessively.
You can read more on the statistical aspect here.