Now that the Thanksgiving feasting is winding down, now would be a great time to tell you that that succulent turkey you’ve been scarfing down for the last couple of days contains measurable amounts of carcinogens. That’s right: your turkey has toxic chemicals that cause cancer. No this isn’t some conspiracy – Big Turkey hasn’t been pumping cancer causing chemicals into the birds. It’s a natural product found in turkeys (in all cooked products, actually), and while the risks are real, they’re actually really low (so go on and continue eating).
Surprisingly, people don’t really like it when I bring this up at mealtimes. And I’ve brought it up enough times to know that you’re probably still concerned and have some questions, so let’s just nip those in the bud while we are here.
Q: How do turkeys naturally have cancer causing chemicals in them?
A: Heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs) are classes of compounds that occur naturally throughout the world (including your turkey). These are diverse groups of chemicals that are all large and perfectly flat, which means they easily insert themselves into your DNA, disrupting the structure and causing DNA damage. This is the first step to cancer (and only the first step).
Q: Is there a way to avoid eating HCAs and PAHs?
A: HCAs and PAHs are natural byproducts formed by incomplete combustion of organic material. If you remember your middle school chemistry class – fires start when a fuel (organic matter) and oxygen combine and rearrange their chemical bonds to form water vapor, carbon dioxide (CO2), which releases a lot of heat. If organic matter is not fully combusted, in addition to CO2 you get things like HCAs and PAHs. Some marinades help reduce HCA and PAH formation and avoiding direct contact to flame (like grilling and barbecue) can also reduce their formation. But since meat is organic matter, and cooking is essentially very inefficient burning, it’s pretty much unavoidable in your plate.
Q: So why doesn’t everyone who has ever eaten a turkey in their life have cancer?
A: Well, part of it is that DNA damage is only the first step to cancer. There are a lot more required before you need to get worried. As it turns out, your DNA gets damaged pretty frequently – UV light damages DNA (hence all the hubbub about sunscreen), and a lot of times DNA gets damaged when your cells are dividing, just by chance. So your cells, in turn, have evolved quite a few ways of repairing your DNA all the time.
Q: But what about those studies that show increased risk of cancer with meat consumption?
A: You mean like those released by the World Health Organization about bacon causing cancer? Okay, yes, like I said before, the risk is low, but it’s still a risk. While your body is capable of defending itself from HCAs and PAHs at any given time, the more meat you eat, the more your body will have to defend itself, meaning eventually your cells may not catch the damaged DNA in time, resulting in cancer. Think of sun exposure as an example – if you go out into the sun more, you’re more likely to get skin cancer because you’re exposing yourself to UV light more than someone who likes to stay inside. So if you eat more meat, you’re exposing yourself more to HCAs and PAHs, then you’re increasing your risk for cancer.
Q: Do I have to stop eating this turkey?
A: Probably not. I certainly haven’t stopped. Like everything else in toxicology, it’s the dose that makes the poison. Too much of anything, even something that’s good for you, eventually becomes bad for you (again, think of sun exposure and skin cancer). But to put things in perspective – the Global Burden of Disease Project estimates 34,000 deaths per year result from diets high in processed meats. In contrast, about 600,000 people die each year from alcohol consumption, 200,000 people die every year from air pollution, and about 1 million people die each year from cancer resulting from smoking. Thanksgiving turkey isn’t really the top of my list of toxic worries.