Smoked foods are delicious, but given that not everyone has access to a smoker, the use of liquid smoke flavoring is increasing in popularity. And the use of liquid smoke flavoring oftentimes seems healthy because it doesn't impart additional calories—just flavor. Smoked food is different: It's cooked at low temperatures with indirect heat (compared to the high and direct heat of grilling). This technique doesn't lead to a large formation of HCA.
However, when wood is burned, polyaromatic hydrocarbons (PAH)—a class of carcinogens—are formed. They're released via smoke and go into the food. The level of PAH in these foods varies, but foods smoked commercially in a manufacturing facility have been found to contain lower levels of PAH compared to ones smoked in non-commercial settings, like your friend’s backyard.
