Cooking food at high temperatures, for example grilling or barbecuing meats, can lead to the formation of minute quantities of many potent carcinogens that are comparable to those found in cigarette smoke (i.e., benzopyrene). Charring of food resembles coking and tobacco pyrolysis, and produces similar carcinogens. There are several carcinogenic pyrolysis products, such as polynuclear aromatic hydrocarbons, which are converted by human enzymes into epoxides, which attach permanently to DNA.
The above statement applies equally to coffee that has been roasted very dark, which is generally pursued when you are using very low grade coffee and the sooty taste is deemed preferable to being able to taste the coffee itself.
We're not health fanatics at Londinium, but we think this issue has been given scant attention to date, whilst caffeine seems to have received a disproportionate amount of coverage and if you believed even half of it you would have thought it would have exterminated the human race long ago.
All things in moderation we say, and if you seek out high quality coffee beans and roast them with care there should be no need to roast them very dark to the point where the bean is beginning to carbonise/turn to charcoal, even if they are intended for espresso use.
The myth that espresso beans must be roasted very dark must not be allowed to perpetuate.
Espresso doesn't need to be burnt or bitter. It can be sweet and delicate.
Try a Londinium roast.
(the only exception to this is our SWP decaffeinated roast where the green beans have already been turned to a dark brown colour by the decaffeination process before we commence roasting). They also seem to require dark roasting to optimise the taste. Otherwise all our roasts are light.