Asked by: Gabrielle Smith, Bedfordshire
It’s long been known that just over-heating, let alone burning, some foods can lead to the formation of compounds linked to cancer. These include heterocyclic amines and so-called polycyclic aromatic hydrocarbons (PAHs), which can lead to fried or smoked foods posing a health risk.
In the case of burnt toast, most concern surrounds the risk from the formation of acrylamide, a compound that has been linked to cancer and nerve damage in animals. That said, the evidence of a direct link between cancer and acrylamide in food consumed by humans is far from compelling. While some studies have pointed to a doubling in risk of ovarian and uterine cancer among women consuming this compound in food, other studies have found nothing.
Even so, in 2007, the European Union’s health advisors decided to take a precautionary approach, and recommended that people avoid eating burnt toast or golden-brown chips as they may contain unacceptably high levels of acrylamide. The UK went further than this in 2017, with The Food Standards Agency (FSA) stating that even brown toast poses an increased risk, advising that toast should be cooked to a golden yellow colour.
Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.