Re: How do Cooked Food Mutagens Work ?

Food mutagens, are or can become highly reactive compounds, which, in this 
case, means that they bind to molecules such as protein, RNA and DNA in the 
body very easily.  This is not a big deal when the binding occurs to 
proteins or RNA, because these can easily be replaced.  If the binding 
occurs to DNA (this is called adduction) and if the adduct is not removed, 
the cell, upon dividing will produce the wrong DNA sequence.  When a cell 
divides to produce a "daughter cell" its DNA must be copied exactly so that 
the daughter cell looks and acts just like its parent.  When DNA is 
adducted, the DNA of the parent cell will not be copied exactly-there will 
be mistakes.  Once a cell divides, the mistake (mutation) becomes permanent 
in the daughter cell and the daughter cell will pass the mutation on when 
it divides.  The mutation may have several consequences: no effect, death 
of the cell, or abnormality of the cell.  Abnormal cells can go on to cause 
cancer in some cases.

Cooked food mutagens can be formed from carbohydrates, fats, proteins or 
combinations of these.  Carbohydrates by themselves or along with amino 
acids can form brown products when heated.  The brown color is due to 
polymer formation in the food.  These reactions include caramelization and 
Maillard Browning.  Examples of this include the browning of sugar when it 
is heated (caramelization) and the browning of bread when toasted (Maillard 
Browning).  Some of the polymers formed are mutagens.

When fats are burned (for example when fat from a grilling hamburger drips 
onto hot coals or flame and produces smoke) compounds known as polycyclic 
aromatic hydrocarbons are formed.  The molecules, when eaten, can be 
"activated" by enzymes in the body, known as Phase I enzymes, to produce a 
highly reactive molecule that can form DNA adducts.

Proteins may react with heat to form compounds known as heterocyclic 
amines.  These, like polycyclic aromatic hydrocarbons, can be activated by 
Phase I enzymes and form DNA adducts.  Because they contain considerable 
amounts of both fat and protein, grilled hamburgers contain both polycyclic 
aromatic hydrocarbons and heterocyclic amines.  Most of these are on the 
outer surface of the burger.

Lysinoalanine is a highly reactive molecule which can be formed by a number 
of food processing operations.  Generally, it is the cause of protein 
degradation, but can cause DNA damage if it comes into contact with DNA.

I have included the URLs for Web Pages that contain information about 
carcinogens, including those which are food mutagens and about 
"bioactivation", the process by which highly reactive molecules are formed 
by Phase I enzymes.

http://dietetics.mcgill.ca/staff/chan/420/lecture11/index.htm 

http://sis.nlm.nih.gov/toxtutr1/amenu.htm 

http://sis.nlm.nih.gov/toxtutr2/amenu.htm 


Hope this helps.  If you have any more questions, please let me know.

Keith Harris