Don't burn the toast and then eat it!
It turns out that eating burnt toast, oven-roasted potatoes and other starchy foods that are cooked at high temperatures can increase your risk of developing cancer, according to the Food Standards Agency in the United Kingdom.
Why? because of something called "Acrylamide," this is what causes bread and potatoes to turn a golden brown when they are fried, baked, toasted or roasted. And golden brown is fine! It's the dark brown/black and crunchy that's a problem. Many animal studies have proven the link between acrylamide and cancer, and while it has never been proven in humans, that doesn't mean there is no risk.
It is impossible to expose people on purpose to acrylamide to test the outcome.
Experts are convinced that if acrylamide is carcinogenic in animals, it is also carcinogenic in humans. It's important to understand that toast and baked potatoes will not give you cancer as long as they are properly prepared.
Follow the "golden rule" in this case. Gold, not brown or black, should be your cooking guide.