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Opinion: What’s in Your Food?

Are the “carcinogenic” chemicals that are produced when foods are cooked really cause for concern?

By | July 16, 2012

image: Opinion: What’s in Your Food? Wikimedia Commons, Jan van der Crabben

Cooking food is the major process adopted to produce flavor chemicals, which give foods a characteristic desirable roasted or toasted flavor. More than 1,000 low molecular weight compounds are known to be produced once a food is heated, and the number of known compounds is increasing steadily. The amounts of these chemicals formed are generally in very trace levels (around the level of µg/kg of food or parts per billion, ppb), but for most of these compounds, detailed information about possible toxicity at this level is not yet established.

One of these compounds is 4-Methylimidazole (4-MEI), which forms from a reaction between amino acids or proteins and sugars, carbohydrates, or lipids when exposed to heat. This past March, an independent study commissioned by the consumer interest group Center for Science in the Public Interest (CSPI) found that four of the best-selling sodas (Coca-Cola, Diet Coke, Pepsi and Diet Pepsi), which use caramel color produced by heating sugar and ammonia, contain potentially unsafe levels of 4-MEI, which according to the report had recently been linked to cancer. “The average amount (138 µg) of [4-MEI] that our tests found in a 12-ounce can of [cola] is 4.8 times greater than California’s 29 µg-per-day limit, indicating a lifetime risk of cancer of 5 out of 100,000 people,” CSPI Executive Director Michael Jacobson wrote in a letter to the US Food and Drug Administration that described the results of the study. This has caused a stir in the consumer research community, with many advocating for the reduction or elimination of 4-MEI from marketed food and drinks.

But I do not believe 4-MEI is harmful at the levels found in these products. Stating that these sodas contain potentially unsafe levels of the chemical is misleading—it is present only trace levels. Furthermore, the supposed cancer link stems solely from a handful of animal experiments; there is currently no evidence of a link between 4-MEI and disease in humans.

I recently conducted a study that demonstrated that adding sulfite, which is one of the most commonly used caramel ingredients, reduces 4-MEI formation. But when we try to reduce 4-MEI, we may have to remove a tremendous number of other desirable chemicals formed in foods by heat treatment. Furthermore, it is important to keep in mind that heat treatment of foods does more than give the food palatable flavors, colors, and textures; heat treatment also kills harmful microorganisms, and it should be stressed that ingesting such microorganisms may cause more toxic effect to humans than ingesting trace levels of 4-MEI.

And this concern over the presence of 4-MEI in popular soda brands is just the latest in the periodic excitement that is stirred up over chemicals that are formed in foods when they undergo processing and cooking. Other potentially carcinogenic chemicals that have raised concerns in the past include polycyclic aromatic hydrocarbons, N-nitrosamines, aromatic amines, and acrylamide. Whenever one of these carcinogens is reported in cooked food, many people from various specialties, including food sciences, regulatory agencies, and medicine, not to mention consumers, react by giving the new chemical concentrated attention and intense discussions about how to reduce it. However, in each case, after some time has passed, attention fades away, in part because there is no practical way to remove these chemicals from cooked or processed foods and also because there is no evidence that the trace levels consumed present any health risk to humans.

It should also be noted that all substances are poisons; only the dose differentiates the poison from a remedy. This concept was developed by Paracelsus, a medical doctor in Europe in the 16th century, and it is useful in evaluating risk in our daily lives by considering examples of well-known substances with low and high toxicity consumed today. For example, water might be considered one of the least toxic substances that we commonly encounter. However, there are many reports of water toxicity in the scientific literature. Too much water can, indeed, be fatal. For example, in 2002 a student was undergoing a fraternity initiation ordeal, in which he was required to drink up to 5 gallons in a short period of time. Consumption of this amount of water resulted in the dilution of the electrolytes in his blood to the point that normal neurological function was lost, and the young man sadly died.

While this example is extreme, the same basic logic must be applied to the toxins that are released in foods during the cooking process. In other words, we must consider not just the chemicals we are ingesting, but how much of those chemicals we consume in our diet. Even well known carcinogens, such as arsenic or nicotine, are only harmful if exposure is high enough. In the case of 4-MEI, the amount present in foods is extremely low and it is hard to predict any kind of adverse health effect at these levels.  People have been consuming numerous heat-induced chemicals, including 4-MEI, since the discovery of fire some half a million years ago, and there has been no clear evidence of any specific health problems to date. Thus, while it is extremely important to continue ongoing research to determine the toxic level of 4-MEI, I personally choose to enjoy flavorful, cooked foods, without fear for my health.

Takayuki Shibamoto is a distinguished professor in the Department of Environmental Toxicology at the University of California, Davis, and an associate editor of Journal of Agricultural and Food Chemistry.

Correction (July 16, 2012): This story has been updated from its previous version to correctly state that parts per billion (ppb) is equivalent to micrograms/kilogram, not milligrams/kilogram. The Scientist regrets the error.

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Comments

Avatar of: mightythor

mightythor

Posts: 1457

July 16, 2012

mg/kg (milligrams per kilogram) is ppm (parts per million), not parts per billion.

Avatar of: TheSciAdmin

TheSciAdmin

Posts: 56

July 16, 2012

Thanks for pointing out this mistake. It has been fixed, and a correction appended.

Thanks for reading!
~Jef Akst, editor, The Scientist

Avatar of: Bruce Toman

Bruce Toman

Posts: 1457

July 16, 2012

Hm!

Avatar of: enrico davoli

enrico davoli

Posts: 1

July 16, 2012

You mean that you don't believe in toxicology in general or you just don't think that 4-MEI limits are appropriate and should be revised? You have specific information or are just guessing?
 

Avatar of: Guest

Anonymous

July 16, 2012

I agree with your comment that toxicity depends on the amount of ingestion. However, I have to disagree with you on the effects of additives, pesticides, flavor enhancers, etc. present in our food. I am one that suffers from many food allergies related to this problem. My health improved after I started eating only organic food. Let's be responsible and don't dismiss the obvious. Granting permission to the food industry to continue making shortcuts to make their products more marketable is reprehensible.

Avatar of: Guest

Anonymous

July 16, 2012

 I agree with your comment that toxicity depends on the amount of ingestion. However, I have to disagree with you on the effects of additives, pesticides, flavor enhancers, etc. present in our food. I am one that suffers from many food allergies related to this problem. My health improved after I started eating only organic food. Let's be responsible and don't dismiss the obvious. Granting permission to the food industry to continue making shortcuts to make their products more marketable is reprehensible.

Avatar of: malenarango

malenarango

Posts: 2

July 16, 2012

 I agree with your comment that toxicity depends on the amount of ingestion. However, I have to disagree with you on the effects of additives, pesticides, flavor enhancers, etc. present in our food. I am one that suffers from many food allergies related to this problem. My health improved after I started eating only organic food. Let's be responsible and don't dismiss the obvious. Granting permission to the food industry to continue making shortcuts to make their products more marketable is reprehensible.

Avatar of: malenarango

malenarango

Posts: 2

July 16, 2012

 I agree with your comment that toxicity depends on the amount of ingestion. However, I have to disagree with you on the effects of additives, pesticides, flavor enhancers, etc. present in our food. I am one that suffers from many food allergies related to this problem. My health improved after I started eating only organic food. Let's be responsible and don't dismiss the obvious. Granting permission to the food industry to continue making shortcuts to make their products more marketable is reprehensible.

Avatar of: hbeierbeck

hbeierbeck

Posts: 4

July 16, 2012

Why worry about a bit of 4-methylimidazole in your soft drinks? The HFCS and artificial sweeteners are the real problems.

Avatar of: Bob_SR_CA

Bob_SR_CA

Posts: 2

July 16, 2012

I read this and came out of it thinking it does not address the issue raised.  Several of his objections to the statement “The average amount (138 µg) of [4-MEI] that out rests found in a 12-ounce can of [cola] is 4.8 times greater than California’s 29 µg-per-day limit, indicating a lifetime risk of cancer of 5 out of 100,000 people,â€쳌 are:

 - That is a "trace" level, as if defining the amount as trace has any relevance what so ever to the factual information provided above, which of course it does not.

-  In lots of other cases like this "after some time has passed, attention fades away" which may be true, but is sad

-  "there is no practical way to remove these chemicals from cooked or processed foods".  If so, one can simply stop eating those foods, sodas being particularly easy to stop eating, I've not drunk a soda in many years.  But my bet is that this potential carcinogen could in fact be removed.

He makes what I assume is a true statement that "the supposed cancer link stems solely from a handful of animal experiments".  If this is true, it is simply a good indication that there is more to investigate, not an indication that we should ignore what evidence there is at hand and assume, as he does, that therefore this chemical is a safe additive.

Avatar of: Bob_SR_CA

Bob_SR_CA

Posts: 2

July 16, 2012

I read this and came out of it thinking it does not address the issue raised.  Several of his objections to the statement “The average amount (138 µg) of [4-MEI] that out rests found in a 12-ounce can of [cola] is 4.8 times greater than California’s 29 µg-per-day limit, indicating a lifetime risk of cancer of 5 out of 100,000 people,â€쳌 are:

 - That is a "trace" level, as if defining the amount as trace has any relevance what so ever to the factual information provided above, which of course it does not.

-  In lots of other cases like this "after some time has passed, attention fades away" which may be true, but is sad

-  "there is no practical way to remove these chemicals from cooked or processed foods".  If so, one can simply stop eating those foods, sodas being particularly easy to stop eating, I've not drunk a soda in many years.  But my bet is that this potential carcinogen could in fact be removed.

He makes what I assume is a true statement that "the supposed cancer link stems solely from a handful of animal experiments".  If this is true, it is simply a good indication that there is more to investigate, not an indication that we should ignore what evidence there is at hand and assume, as he does, that therefore this chemical is a safe additive.

Avatar of: Warren

Warren

Posts: 1457

July 17, 2012

While this article is about processed food, the bogey of the latest potential carcinogen to be identified and quantified in bbqd, roasted, toasted, preserved food ... is regularly raised in the media. I presume the food that our ancestors cooked by throwing on an open fires contained a range degradation products that would would turn modern hairs. Aren't we observing the interaction of the increased chance of developing a disease such as cancer from our longer lives, the improved detection and quantification of trace organic constituients and toxicological data inadequate for the assessments being demanded by consumers.

Avatar of: Jaroslav Stravhosky

Jaroslav Stravhosky

Posts: 1457

July 17, 2012

"It should also be noted that all substances are poisons; only the dose differentiates the poison from a remedy." - Professor Takayuki Shibamoto
So a specific dose of mercury is equal to the same dose of say, table salt? This from a "distinguished professor in the Department of Environmental Toxicology at the University of California and an associate editor of Journal of Agricultural and Food Chemistry?" Thank you professor for enlightening us as to why people need to do their own research instead of trusting the so-called "experts."

Avatar of: Suciu Alexandru

Suciu Alexandru

Posts: 1457

July 20, 2012

OK, but this is the idea:
this very low concentration of many chemicals, not only resulted from
cooking but some food additives and chemicals from the environment too,
keeps our body busy eliminating them instead of fighting reducing cancer
cells we all produce in our body every day. It`s about we ingest a very
low concentration of each of these thousands (perhaps tens of
thousands) of chemicals every day and as the number of these chemicals
increases our body needs more effort to neutralize and eliminate them.
And it`s about, and it`s very important, the genetic package too. It`s
true the concentrations are very low (ppb) and our organism is adaptable
but we must not ignore that nowadays the incidence of cancer and other
diseases is high and perhaps our rate of adaptability is overwhelmed by
the rate at which our organism is bombarded with chemicals...

Avatar of: Andrew Booth

Andrew Booth

Posts: 1457

July 22, 2012

When did nicotine become carcinogenic? You might have corrected that error.

Avatar of: Padraig Hogan

Padraig Hogan

Posts: 5

July 23, 2012

I am of the view that cooking food in any way is unnatural and not what we are evolved to eat at all. 

I am also of the view that we live much shorter lives today than our earliest ancestors did (provided they didn't get eaten), and that diseases such as cancer barely existed in those times. The idea that paleo man (before he started cooking) lived short, brutal lives is an absurd myth not backed up by evidence. Generally speaking non-primates today are in very good shape/health until the day they die in old age... unless they are introduced to human food. And I find your final sentence to have a "weird" and convoluted structure.  

Avatar of: Whyking

Whyking

Posts: 1

July 30, 2012

Nicotine is NOT a carcinogen, though a poisson .

Avatar of: Brett Rudman

Brett Rudman

Posts: 1457

August 30, 2012

"And this concern over the presence of 4-MEI in popular soda brands is just the latest in the periodic excitement that is stirred up over chemicals that are formed in foods when they undergo processing and cooking. "

I am not in the habit of using ammonia as a kitchen staple. While trace elements of harmful compounds are certainly created during normal cooking processes, it is the foods created and processed in labs that we should try to eliminate/reduce. Getting back to real cooking with real ingredients! It is not that difficult a concept.

July 4, 2013

As others have commented, this article dosn't read as though it were written by a professor of toxicology and editor of a major journal.

He should have made it clear that there are, broadly, two kinds of chemical carcinogens: those that act by classical toxicolological mechanisms, with a sigmoid dose-response curve, and those that react directly with DNA in a way that can cause mutations. He doesn't say into which class 4-MEI (or more likely a metabolite) falls.

Official policy is that each DNA-damaging event caused by a DNA-reactive compound carries the same risk of the cell becoming cancerous, and there is no such thing as a dose with zero risk. A good account can be found in the WHO Guidelines for Drinking-water Quality, 4th edition.

Too many people repeat that Paracelsus nonsense when they should know better; perhaps they're just short of an argument. There is some evidence from in vitro experiments that DNA repair (or other mechanisms) may result in negligible risk for low doses, but there is no way that can be transposed into laws or regulations. There is a contrary opinion that the "one-hit" (linear dose-response) model applies to the better-studied case of low-dose ionising radiation, the effects of which due mainly to reactive chemicals (radiolysis products).

To conclude, the incidence of cancer has been increasing, taking into account the usual demographic effects. We don't know if this is due to increased exposure to chemicals (natural, formed during food processing, synthetic or semisynthetic). It might be due to viruses, for example. I've tried to wrrite a dispassionate account of the uncertainties and would welcome proposals for improvements: www.genotox.chrblee.net.

Avatar of: BHowd

BHowd

Posts: 2

July 4, 2013

It's not clear to me why this year-old article was reprinted.  It represents a rationale opinion, but from a non-toxicologist, with no apparent experience in cancer risk assessment.  There are many excellent toxicologists at UC Davis who would have some fundamental disagreements with their colleague in Agricultural Chemistry, as I do also.

I agree that we need to consider relative risks of the many chemicals in our food which can have adverse effects, but let's not throw out the basic cancer risk assessment principles when doing so. 

Bob Howd

 

 

 

 

Avatar of: anupama_ifp

anupama_ifp

Posts: 6

July 5, 2013

very disappointing as many others already commented - certainly doesnt justify the title

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