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Does burnt food cause cancer?

Does burnt food cause cancer? Someone said to me that burnt food was "as dangerous as a cigarette", which is a pretty big claim, so I've been searching the web and some research databases, looking for evidence.

There's very little on the web about it, besides a lot of idle speculation on messageboards. This ScienceNews article from 2005 says that the US government now lists certain chemicals found in "meats when they're cooked too long at high temperature" as carcinogenic. It also says:

Finally, the report notes that while inconclusive, published studies in people "provide some indication" of human risks from eating broiled [grilled] or fried foods "that may contain IQ and/or other heterocyclic amines." The National Cancer Institute conducted one of those suggestive studies. It compared the diets of 176 stomach cancer patients and another 503 cancerfree individuals. Overall, people who regularly ate their beef medium-well or well-done faced more than three times the stomach cancer risk of those who ate their meat rare or medium-rare, according to a 1997 report of the research.

More information about this is in a very helpful summary by the USA National Cancer Institute. Note that one of the studies quoted looked at cooking at 200ºC or 250ºC, which is much hotter than ordinary baking/roasting. However, that is the kind of temperature you use to cook a pizza...

Statistics like "three times the cancer risk" always sound scary, but you need to ask, three times what? We need to know how the risk compares against other things. More on that later.

I found a messageboard thread on which someone said "You can put tomato sauce on it. I heard it helps lessen the production of carcinogen which causes the cancer." This is a big mistake. Fruits like tomatoes or cherries do contain antioxidants which counteract the formation of the carcinogens, but only during the cooking process, mixed in with the meat (e.g. in a burger mixture). Putting ketchup on afterwards will make zero difference.

I also found a journal article discussing the increased cancer risk from barbecued food especially (Lijinsky W, (1991), Mutation Research 259 (3-4): 251-261). It suggested that the reason for the risk was that fat will drip off the meat, then burn at high temperatures when it hits the coals, forming the cancer-causing substances that then mix in with the barbecue smoke and may then coat the outside of the meat being cooked. This explanation was proposed to explain their finding that the chemicals were mainly found in fattier foods cooked over burning logs.

Other relevant journal articles:

  1. One found a similar connection: the highest concentrations found in the Italian diet were in pizzas cooked in wood-burning ovens, and in barbecued beef and pork. Ludovici M et al (1995), Food Additives and Contaminants 12 (5): 703-713)
  2. One found that the Indian tradition of cooking with homemade clay-stoves, called "Chulha", created a lot of smoke containing the problematic chemicals.(Bhargava A et al (2004), Atmospheric Environment 38 (28): 4761-4767) This was said to increase the risk for people who cook with them - remember that inhaling carcinogens is typically much more dodgy than swallowing them, because the route into the body is more direct.

The relative risk? Is a barbecued steak as dangerous as a cigarette, as certain internet message boards might lead you to believe? Clearly not: many people eat well-cooked meat, yet nine-out-of-ten cancer deaths can be attributed to smoking. (The nine-out-of-ten figure comes from a study of USA deaths in 1995: source.) Scientists can calculate guideline statistics such as the "incremental cancer risk", an averaged-out measure of the risk from something. For cigarettes it's 0.079 (source); for burnt meat it's somewhere between 0.00001 and 0.00038 (source). So the risk is somewhere between 200 and 8000 times lower - there's no comparison between one cigarette and one burnt steak.

My conclusions:

  1. Regularly eating burnt or barbecued meat, especially meat that's been cooked at high temperatures for a long time, is relatively risky behaviour. But don't panic: it's not comparable to smoking.
  2. For non-meat food the research is less clear-cut: it's not obvious whether all smoke-cooked or overcooked food carries risks. Certainly if you don't eat it regularly there's nothing to worry about.
Monday 2nd October 2006 | science | Permalink
Name: Carolyn Porter
Email: cporter4 art cherrycreekschools dort org
Date: Tuesday 3rd April 2007 17:29
Thank you for your blog. I am a biology teacher and I was trying to find out more info on this very topic because I know my students will have bunches of questions. Your links within the blog are very helpful. I always tell my students: Everything in moderation!
Name: Andrew Brown
Date: Wednesday 4th July 2007 13:59
Thank you; because of this, I just ate my burnt chicken. It didn't taste very nice, but I didn't want to cook more.
Name: bruce sylvia
Website: http://none
Email: noeticus_society art yahoo dort com
Date: Thursday 20th September 2007 18:44
thank you for your report,my question is; does eating burnt toast have any cancer causing agents? my son said he read a item in the paper that said it might. you know that they say just about everthing causes cancer. thank you for your time in responding to my email,bruce sylvia, homonoeticus
Name: Phil Treseder
Website: http://hhtp://none
Email: philip art treseder dort eclipse dort co dort uk
Date: Friday 16th November 2007 19:51
My wife has been on to me about this subject for some time. I have a gas Barbie. Obviously, if you cook decent slabs ob Beef, Pork or Lamb, as to the nature of a good piece of meat, it must contain some fat and thus create some burning.
On reading the info and that on refgerenced websites it seems that the combination of chemicals in wood/charcoal smoke combined with the fat could cause the problem.
The other point is that, as the meat is cooking, the fat ouses out, gets carcified and then drips off. Unless you realy crem the meat then there is only a ninescule amount of carcinogens left on the meat. p.s no comment on the spellows, Ive just been cooking some Lamb steaks and sipping on a good Merlot.
Name: queenie
Email: idiot262 art yahoo dort com dort sg
Date: Friday 4th July 2008 13:01
how abt burnt chicken nuggets?
Name: Josh
Date: Wednesday 23rd July 2008 10:12
This is NONSENSE. The people who GET cancer are the people who worry about this type of over-speculation. Don't be a news reporter. This article has no good effect on ANYONE.
Name: Rico
Email: cho-cobo64 art hotmail dort com
Date: Thursday 19th February 2009 00:03
Nice, my parents have been telling me this for some time now. Now I'm going to be more cautious about my burnt food, EVEN IF IT TASTES SO GOOD WHEN IT'S A BIT BURNT =(. Anyway thanks for the article, the guy who posted a comment on Wednesday 23rd July 2008 10:12 doesn't know what he's talking about.
Name: barry
Email: barry689gallagher art btinternet dort com
Date: Saturday 21st February 2009 14:59
I think there should be no risk because the body will reject the burnt bits of food inside the body and take any nutrients from it, in fact it shoud be healthier because your filling your hunger but not getting as much fat in your system, ie the fats already burnt !
Name: Thomas
Email: hukclefish art yahoo dort com
Date: Sunday 15th March 2009 20:02
9 out of 10 cancer deaths are NOT directly related to cigarette smoking.

Perhaps lung cancers but not cancer as a whole - you should update the article to correct your error.
Name: Xavier
Website: http://www.cielodeaustin.com
Email: xrenter art gmail dort com
Date: Sunday 24th May 2009 11:05
Does this mean I have to microwave tortillas now instead of placing them over the gas fire?
Name: ananda hota
Date: Friday 28th August 2009 07:50
I did nit read the article of Bhargava et al. 2004 in detail but, it does not seem to say any carcinogenic nature of burnt food, it is talking about the chemical produced by the smoke which produced by burning bio-mass like wood and dry cow dung.
Having said that, if smoke from wood burning can have the chemical, I suspect that burning any part of plant can also cause the similar, so seems that boiling in water is much better than BBQ...Thanks for bringing authentic sources to the internet.
Name: andy
Website: http://www.strangeicehotel.com
Email: andyng_728 art hotmail dort co dort uk
Date: Sunday 20th December 2009 22:48
yes this is a good topic to revise on :) i only 13 years old tho so yer... my friends and bro been arguing wether burnt food will cause cancer (toast) me ans my bro recon yer it will increase the risk of getting cancer
Name: Leif Husman
Email: rellicke art aol dort com
Date: Monday 21st December 2009 18:01
Thank you. I was ready to sift through dozens of from-the-hip opinions before finding relevant info on "burnt food carcinogens" but yours was the first site I came to. My BS detector reads negative :-)
Name: Anon...
Date: Friday 15th January 2010 08:58
i have recently bought a brita water filter that uses a carbon filter made from burnt coconut shells, dust is normally present when first using a filter, i imagine trace amounts of carbon dust are ingested. what about the carbon- cancer studies out there?? anyone know?? isn't that why the burnt stuff id bad for you??
Name: david Wilson
Email: wildfind art gmail dort com
Date: Tuesday 26th January 2010 12:54
Some good epidemiological evidence for the stomach cancer/burnt meat connection; Darwin, in his 'Travels with the Beagle', notes that the Argentinian gauchos, who ate little else but beef cooked in the embers of wood fires,all expected to die of intestinal cancer before the age of forty...
Name: paul
Email: paulking art mypashmina dort co dort uk
Date: Saturday 1st May 2010 09:43
so with 0.079 for cigarettes and between 0.0001 and 0.0038 for burnt meat, how does this compare to spending some time in the sunshine?
Name: tetsusaiga
Email: tetsusaiga83 art gmail dort com
Date: Friday 9th July 2010 02:39
everything the average human likes causes cancer. to be immune to somthing requires evolution, normal stuff you would find in the environment does not cause cancer unless you go digging insainly deep holes looking for it. if we lived on a planet that had all ways been made of asbestos we would use it for nutrients probably... so yes burnt food causes cancer, probably equal to a few hundred cigarettes. ive never seen a smoker cough up anything that black... seriously if you smoked anything else would you even live? tobbaco is close to the safest burnt stuff you can do, try smoking paper cups, napkins, tree bark, tomatos, whatever and see how long you live.. probably not as long as tobbaco.. maybe pot you'd be ok cause it contains cancer fighting agents, possibly enough to break even...
Name: Marco M.
Email: fm dort marcom art gmail dort com
Date: Thursday 9th September 2010 20:25
I came across a researched article a few years ago in which it explained a clinical result that people eating any meaty food especially beef when barbecued on the grill will cause cancer. The researched explains when the meat touches the grills which are over 400 deg. F, the fat content on the surface of the meat gets burnt during the cooking and that's a lot of burnt fat for the life of a person who eats regularly barbecued stakes, hamburger and related beefy food. I like to ask people out there if they may have a copy of it, please email me. Thanks to all the people who participated in this life saving discussion. I have tried very hard to remember the name of the research institute, but I could not.
Name: Carl
Email: aielloc art erau dort edu
Date: Monday 10th January 2011 21:42
For the past few years I've been eating my homefries and sausage with breakfast burnt. I eat my toast unburnt. I don't like raw or rare meat so I often order my prime rib or filet mignon well done and butterflied. On January 1, 2011, the owner of the restaurant where I would get my 'sacrificial' breakfast said she would never in her lifetime serve something like that. The next day, I decided to tone it down a bit and will be content with crispy homefries and well but still with juices sausage.
Email: tiggerdeb art hotmail dort com
Date: Saturday 15th January 2011 02:17
Got a question. I understand all that has been written about burning the meat and all. Question: Sometimes I overcook my microwave popcorn but I eat it anyways. I like it but not a bag full!! Does this have the same chemical effect as it does on meat? I just thought all it was doing just burning some of the oil or butter off the popcorn. Thanks Debbie
Name: Dan
Date: Saturday 15th January 2011 10:42
Frankly Debbie I don't know, but microwave cooking is chemically/physically very different from other types of cooking (it heats up the water molecules from inside) so you probably can't guess much about microwaving, from the research literature on grilling.
Name: Pam
Email: pamhub22 art hotmail dort com
Date: Wednesday 6th April 2011 04:10
I have read all the comments but none have answered my question,, what are the effects if you eat food that has been cooking on top of the stove and you burnt the pot and the food gets burnt and an acidic or toxic taste of horrible smoke, , after eating leaves a burning feeling in your throat,, Is this bad for you
Name: emma
Email: pi_pom art yahoo dort ca
Date: Friday 29th July 2011 19:11
to Pam:
by the way you're describing it it sounds very unhealthy
Name: sand
Email: ssinghnd03 art yahoo dort com
Date: Wednesday 10th August 2011 17:08
eat raw meats like animals and after couple of generations E.coli and stuff like that will not have any effect on your descendants. Or stop eating meat and eat raw vegetables - find another protein source - hopefully it will work for you and your family. Let me get back to my well done lamb chops, fried rice and scotch on the rocks.
Name: terri
Email: bones88 art hotmail dort com
Date: Saturday 10th September 2011 04:02
burnt popcorn in and inclosed area has a strong chemical smell and casues burning in the eyes and throat. Ir occuring on a regular basis is this a danger for people breathing the burnt fumes from popcorn. no more brunt popcorn at the officl
Name: lis
Website: http://colon cleanse using activated charcoal.
Email: fit04life art gmail dort com
Date: Tuesday 13th December 2011 09:16
homeopathic medicine makes claims that taking in charcoal is a useful way to cleanse to lower intestine. It has been said that hospitals use this to neutralize poisons (charcoal has absorptive properties) in the emergency room. It goes on to stating how a colon cleanse will help alleviate build up of plaque (feces) in the colon to prevent cancer. Any comments? The specific chacoal is made from organic foods (coconut shells), and it is stated that vegetable forms of carbon are safe for ingestion by humans.
Name: Dareen AbouShackra
Website: http://www.IngeniousHealth.com
Email: abousha dort dareen art gmail dort com
Date: Monday 27th February 2012 14:00
From what I know, once burnt food is formed - mostly carbon molecules are formed. Burnt food is considered carcinogenic, simply because the carbon molecules have the ability to disrupt our dna, it's able to break portions of DNA and insert itself within... this leads to our dna reproducing it self 'wrongfully' with a different structure.. potentially causing cancer.
Name: Carol Ramadikela
Email: dike2caro art gmail dort com
Date: Wednesday 15th August 2012 20:01
I inhaled smoke frm burnt food(spinach,onion n potato). I ws cooking then dozed off 2 sleep as I ws watching Tv.I woke up 2 find a heavy cloud of smoke in my small room because of a ringing cellphone! My stomach had pains that night. Is there any danger concerning this?

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