What’s wrong with burnt food?

We often hear about the effects of carcinogens from charred or burnt food, and the relationship between carcinogens and cancer. So if you’re wondering if eating this stuff causes cancer, keep reading…

I can tell you two things for sure:

1. Charred food has less nutritional value and calorific value than unburnt food

2. Charred food contains more carcinogens

Let me explain these things in more detail. 

Lower nutritional and calorific value explained

Imagine a piece of food, any kind. If you eat it fresh and uncooked you get the full benefit of its nutritional and calorific value, plus the base load of natural carcinogens.

But not everyone eats everything raw,

some foods just aren’t safe raw, and some don’t taste any good raw, and those are compelling reasons for cooking.

Now think of cooking that piece of food, any way you like, but keep on cooking it until it starts to smoke and turn black, on the way to a piece of food-shaped charcoal.

Don’t stop there, even if you are one that doesn’t mind the odd piece of blackened toast before rushing for the bus. Keep the heat on and watch that imaginary piece of food reduce to a dry pile of ash.

The same happens to any organic matter; a plant, a piece of wood, a vegetable, or a fillet of steak. Heat it for long enough, without allowing it to catch fire, and it will blacken, progress to charcoal, and then reduce to ash. Ash is the end of the line for organic material; no moisture, no volatile constituents, and no more calorific value left.

So, on the one extreme we have raw food and on the other we have ash. It becomes intuitive that the cooking part in between simply cannot add anything to the food in terms of value.

But cooking does add carcinogens; different types of carcinogens, and it does increase the concentrations of carcinogens in food. 

What are carcinogens?

Carcinogens are a range of substances, organic and inorganic, that are directly involved in causing cancer (read more here).

The list of substances “carcinogenic to humans” is ominously long, then there’s a list below that one of “known to be human carcinogens”, followed by another list of substances “probably carcinogenic to humans” plus (as if the first three lists weren’t enough to worry about!) there are all the substances presently classified as “reasonably anticipated to be human carcinogens” (1).

It’s important to realize that not all carcinogens are man-made. They occur frequently and naturally in the environment; like sunlight shines on your skin. Too much can kill. Need I say more?

So there are natural and unnatural carcinogens in the air we breathe, in our soils, and in the water we drink or need to irrigate our crops.

Therefore, carcinogens come with the food we eat, either as natural or unnatural components of the food, or as contaminants on the food. 

The fact is; many foods, no matter how organically they are claimed to be produced, or no matter how diligently they are washed after harvest, or carefully transported and stored, cannot be claimed to be free of carcinogens - unless they are tested to prove otherwise. In other words, it’s common to find small amounts of carcinogens in foods. 

So what?

“Practically anything can lead to cancer,” some say. “Why worry if there’s nothing you can do about it?”

The point is you can do something about it. It’s called risk management, or risk minimization. And some strategies could be life-savers for people with a high cancer risk as a result of their genetic predispositions, lifestyle habits, occupational hazards, or all of the above.

Despite that some may still retort, “Then that’s life, get over it.” Okay, thanks. You can stop reading now.

But if you’re asking, “What can I do to minimize food carcinogens?” then read on, because I hope to give you some more important information. 

Recap on burnt food

So far, you know that there is a base load of dietary carcinogens, and that base load is related to your food selection and the environmental factors prevailing over your food (2) from its source to your kitchen, including whatever happens to that food during transportation and storage.

Now, I should tell you that you’re going to add carcinogens to that base load by cooking your food, but the amount you add (how many types of carcinogens) and the concentrations that you will add (more carcinogen per serve of food) are influenced by the way you cook that food. (3)(4).

For example, a study was done on duck breasts to show that smoking the flesh resulted in the highest concentrations of carcinogens (which is most probably because of the smoke contribution – as a rule smoke will contain carcinogens).

Next in line came charcoal grilled duck breasts without skin, and then charcoal grilling with skin, then came roasting, followed by steaming (5). 

Cooking and the Maillard reactions

Ah ... that word leaves me dreaming of mouth-watering and appetite-inducing aromas; bread or cookies almost ready to take from the oven, meat sizzling on the grill, pears stewing, and coffee beans roasting.

These are the wonderfully tangible results of a complex series of chemical reactions called Maillard reactions. What’s happening is amino acids (chemical compounds that are essential to life) react with reducing sugars (any sugar like glucose, fructose, and lactose but not sucrose) in the presence of heat in excess of 155 °C (310 °F) (6) to produce a range of poorly characterized molecules responsible for those flavors we love to chase.

But the Maillard reaction stage is both a delicious and delicate time.

Prolonged heat or temperatures too high will quite suddenly change those precious golden browns to tarry black. Then, you have burnt food.

And you know by the acrid smelling smoke, without even peeking into the oven, that you’ve overdone it. 

Cooking and Pyrolysis

I’d rush to open the windows, turn up the extractor fan, wave a towel around the smoke detector cursing, “Dang it! I’ve burnt it. Again.”

Nobody likes that burnt food smell, it’s unhealthy too – inhaling burnt food odors is like mainlining carcinogens via your lungs into your blood supply – and … embarrassing.

But a food geek would say say, “Neat. You’ve taken your meal beyond the Maillard reactions into pyrolysis.”

And their multitude of research papers says it all; those much-loved, yet poorly characterised, Maillard reaction products have been transformed into carcinogenic compounds including a range of polycyclic aromatic hydrocarbons (PAH), the same compounds you get in coal tar, tobacco smoke, wood smoke, and in by-products of fuel (fossil or biofuel) combustion (examples of carcinogens).

The same happens to any organic matter, including your once-meal.

Here is the simple translation

Once parts of your meal start to smoke and get black bits you are in the business of making carcinogens. If you don’t remove that meal from heat immediately your burnt food will continue to form more carcinogens and accumulate them in higher concentrations.

At the same time, you’re destroying the last of your food’s nutritional value and its calorific value.

Sounds like a double whammy to your health, if not your risk of cancer.

7 tips to minimise your risk

Here are seven tips to reduce your intake of burnt food toxins:

1. Reduce the base load of carcinogens in your food by selecting types of food that are less prone to contain carcinogens and environmental contaminants

2. Cook with steam as often as possible, and cook quickly 

3. Avoid smoked foods including ham, bacon, salmon etc.

4. Avoid using excessive heat during roasting, grilling, toasting, frying etc.

5. Remove your meal from heat as it reaches a light golden brown colour rather than waiting until it's black - burnt food!

6. Use clean appliances because burnt on food will contribute to the overall carcinogen load

7. Avoid char-grilled or otherwise heat-blackened meals and, while you are at it, avoid inhaling fumes from burnt food or the smoke from burning food

8. If you must salvage accidentally burnt food; excise, cut out, remove, or scrape off all visibly blackened bits before you eat it - otherwise keep on overcooking it – you may qualify it for an exhibit at the Museum of Burnt Food!

Article by John White, BSc (Hons) 


1. American Cancer Society, website, July 2011

2. Foods grown in areas with PAH-contaminated soil or air may contain higher levels of PAHs. Charbroiled meat or fish and smoked foods (meats and cheeses) have higher levels of PAHs. Prepared by Elizabeth Woodard, M.D., M.P.H., BCERF Research Associate and Suzanne M. Snedeker, Ph.D., BCERF Research Project Leader. and the Program on Breast Cancer and Environmental Risk Factors in New York State Cornell University, July 2001

3. Sugimura T, Wakabayashi K, Nakagama H, Nagao M (2004). "Heterocyclic amines: Mutagens/carcinogens produced during cooking of meat and fish". Cancer Sci. 95 (4): 290–9. doi:10.1111/j.1349-7006.2004.tb03205.x. PMID 15072585Kfpsa

4. Mutagens and carcinogens in cooked food, A.R. Liss, New York (USA), 1986, Sugimura, T.; Sato, S.; Ohgaki, H.; Takayama, S.; Nagao, M.; Wakabayashi, K.

5. Chen, B.H., and Lin, Y.S., 1997. Formation of Polycyclic Aromatic Hydrocarbons during processing of duck meat. J. Agric. Food Chem., 45, 1394-1403 

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