The number of emerging organic and inorganic substances, which are called xenobiotic, is increasing day after day. The potential hazards of these substances are being tested since they are used as drugs and food additives. According to the data obtained from these tests, the harmless ones are released for use. However, it should be noted that these compounds, which are taken as drugs or food additives, are mostly biotransformed with cytochrome P450 in the liver. A large portion of different xenobiotic molecular structures that were biotransformed in the liver can be emptied into the small intestine by a biliary duct and can reenter the organism in their transformed molecular structure. Therefore, it should be accepted that the effects of transformed molecular structures of food additives, especially bread additives, to human must be researched.