I was tempted to say, 鈥渨hy don鈥檛 you buy the book,鈥� but that sounded a bit too self-serving. So, let me dig into the science which centers around a small molecule called acrylamide. The International Agency for Research on Cancer (IARC) has placed acrylamide in its Category 2B reserved for 鈥渟ubstances that are possibly carcinogenic to humans.鈥� That raises eyebrows when we learn that this possible carcinogen can be found in many common foods. Think French fries, cereals, potato chips, toast and yikes鈥offee.
Acrylamide forms when the amino acid asparagine and some sugars, mainly glucose, fructose and galactose are heated together to a high temperature. Since asparagine and these sugars are present in many foods and since roasting, baking and frying are common cooking techniques, ingestion of acrylamide is unavoidable. But how much should we worry about its carcinogenicity?聽
Let鈥檚 trace the 鈥減ossibly carcinogenic to humans鈥� issue. It all starts with mice. The animals are treated with increasing doses of the chemical in question, in this case acrylamide, until some adverse effect is noted. With acrylamide that adverse effect is tumour formation in multiple organs. Furthermore, there is a dose-response relationship, meaning that the effect is greater as the dose increases. Add to this a possible mechanism that can explain the onset of cancer, and we have a 鈥渃arcinogen.鈥� That mechanism involves conversion of acrylamide to glycidamide in the liver and this in turn binds to DNA causing mutations and initiating the cancer process.
The takeaway here is that acrylamide can cause cancer under some conditions. In no way do these rodent studies mean that consuming foods that contain acrylamide causes cancer in humans. As always when it comes to questions of toxicity, we have to consider the dose. In rodents treated with acrylamide, usually in their drinking water, carcinogenic effects begin to be noted when they have consumed about 0.5 mg per kg body weight per day.
The acrylamide content of many foods has been determined in the lab and human exposure can be calculated from food frequency questionnaires. Typical human exposure turns out to be about 0.3 to 0.6 micrograms per kg body weight per day. This is a thousand times less than the minimal dose that can cause cancer in test animals! That is comforting and is backed up by a large number of human studies that have found no correlation between calculated acrylamide in the diet and cancer. One likely reason for this is that our bodies are equipped with enzymes that detoxify foreign substances and others that repair damaged DNA.聽
Still, it is conceivable that if these mechanisms are overrun by significant and regular ingestion of acrylamide, there could be consequences. Potato chips, vegetable crisps, crackers and French fries are common sources of acrylamide. Interestingly, if potatoes are stored in the fridge, they are more likely to produce acrylamide because of what is known as 鈥渃old induced sweetening.鈥� Starch is broken down to yield glucose that can readily react with asparagine when heated to a high temperature. Boiled or microwaved potatoes do not produce acrylamide. Neither do fresh cut potatoes that have been soaked in water since much of any glucose present will dissolve in the water. If you are going to make French fries at home, soak them in water first and fry only until light brown. As a general rule, it is better to cook food at low temperatures for other reasons as well. High temperatures produce 鈥減olycyclic aromatic compounds鈥� that are known carcinogens. Stewing or boiling is preferable to frying or baking.
Now how about that toast? As far as I know, nobody has tested lightly toasted bread versus burnt toast for acrylamide content, but there is no doubt the darker the toast the more of it forms. So, I think 鈥渄on鈥檛 burn your toast鈥� is good advice. At least don鈥檛 do it on a regular basis. Also, if you are having coffee with that toast, use lightly toasted beans instead of dark roast.
Should you want to know more about acrylamide, as well as a host of other topics, well, what can I say, get the book.
