Posted on Aug. 15, 2016, 6 a.m. in Cancer Nutrition – http://www.worldhealth.net
“Do you hesitate to eat a plate of barbecued food that has been blackened, because of the common belief that burned food could possibly cause cancer?
Acrylamide is a chemical molecule that forms when food is cooked at high temperatures. However, while it is known to be a potential carcinogen and toxic in its industrial form, it is less clear what the link is between consuming it in food and developing cancer.
Almost 20 years ago, construction workers building a tunnel, through the Hallandsåsridge on southern Sweden’s Bjäre peninsula, noticed that nearby cows were showing strange symptoms, staggering, collapsing, and some even dying. An investigation showed that they had been drinking contaminated water from a stream, and that the contamination was from acrylamide. The workers were using its polymer, polyacrylamide, as a sealant for cracks. This was safe. However, the polymer-forming reaction was not complete, causing some unreacted acrylamide to still be present.
How is acrylamide formed?
Both the workers and a control group who had no known exposure to industrial acrylamide had their blood tested, and both had unsafe amounts of acrylamide. The chemical was then found in fried potatoes, coffee, and especially in carbohydrate-rich foods, but not protein-rich ones. It was in foods that had been heated above 250°F, that were roasted, fried, or baked. However, it was thought that Acrylamide must always have been formed in these types of foods, ever since the invention of cooking. It isn’t found in uncooked or boiled food and less likely in meat, dairy, and fish. It doesn’t matter if the food is “organic” because it is the type of food that counts.
Other chemicals in meat
Of concern are polycyclic aromatic hydrocarbons (PAHs), formed when meat juices and fat drip onto flames, and heterocyclic amines (HCAs) from reactions between molecules including sugars and amino-acids.
How should food be cooked, and is it a carcinogen?
Cook food until it turns yellow, but not brown or black. This restricts the formation of acrylamide. Although scientists identified the source of acrylamide, they haven’t been able to definitely establish that it is a carcinogen for humans when consumed at levels normally found in cooked food. A 2015 review of data came to the conclusion that “dietary acrylamide is not related to the risk of most common cancers”. However, it did add that a modest association for ovarian, kidney, and endometrial cancers in people who had never smoked could not be ruled out. Some studies have shown that meat that has been fried, burned, or barbecued has a higher possibility of certain cancers, but these links are hard to prove.
What should you do?
If you have concerns, you can reduce exposure by cooking in a microwave oven instead of over flames and regularly turning the meat. The food may not be as tasty, because grilling, toasting or baking produce many molecules that enhance flavor. Also, marinating meats in beer before grilling them helps to reduce levels of cancer-causing compounds. Eat less meat, or use vegetables instead to replace the meat when grilling. If you have a healthy diet with plenty of vegetables, fruit, and whole grain food, none of those contain acrylamide.”
LES COPELAND, Professor of Agriculture at the University of Sydney.
THE CONVERSATION – Business Insider Australia
OCT 12, 2016
“Have you ever wondered how freshly baked bread gets its a golden brown crust and why it smells so good? Or how nondescript green berries turn into beautiful brown coffee beans with a rich alluring aroma?
The answers to these questions lie in a series of complex of chemical reactions, known as Maillard reactions, which give many foods their familiar flavours and colours. These sensory properties even guide us in how we choose foods and help create our initial perceptions of their quality.
As the name suggests, Maillard reactions were first described by a French physician and biochemist, Louis-Camille Maillard, in 1912. These reactions produce hundreds of chemical compounds that give colour and aroma to some of our favourite foods such as roast meat, potato chips, bread and other bakery products, coffee, chocolate and confectionery.
Maillard reactions occur between amine groups of amino acids or proteins and “reducing” sugars, such as glucose and fructose. These sugars are so named because they act as chemical reducing agents.
These reactions occur most rapidly under conditions of low moisture and at temperatures above about 130℃. Hence, they tend to kick in when we fry, bake, grill or roast.
Maillard reactions are also referred to as browning reactions because of the colour they impart to foods cooked in this way. When meat is grilled or roasted, only the surface is usually hot enough to cause browning. The interior can retain a pinkish colour because the cooking temperature stays below that required for Maillard reactions to occur rapidly.
Foods cooked by boiling or steaming do not turn brown or acquire the complexity of flavours because the temperature only reaches about 100℃. Likewise with cooking in a microwave oven.
The colour of chocolates, fudges and toffees are produced by the reaction of sugars with milk proteins.
The initial products of Maillard reactions are small volatile molecules, which are responsible for the aromas we get from freshly baked bread and coffee. More complex reactions then take place to form larger molecules responsible for the golden to brown colours. This is why the aroma of baking bread is sensed before the crust browns.
The later Maillard reactions are not well understood. We do know that some of the molecules they form have unpleasant flavours and may even be toxic, or the source of carcinogens that occur in charred meat.
The colour of flavour
A common misconception is that Maillard reactions are the same as caramelisation. Although both are favoured by conditions of low moisture, caramelisation occurs when sugars are heated to high temperatures in the absence of proteins. The common food flavour and caramel colour is produced by heating a mixture of glucose and sucrose to 160℃.
Maillard reactions don’t only take place in a hot oven though. They can also occur slowly at ambient temperature, resulting in gradual changes to aroma, flavour, colour, appearance, texture, shelf-life and nutritional value of stored foods.
In this way, Maillard reactions are responsible for the colour of honey, as well as deterioration during storage of dry goods such as flour and powdered milk. Maillard reactions are also implicated in the gradual loss of viability of seeds.
Maillard reactions can also have detrimental consequences. Unsightly blemishes may appear on chips after frying if their reducing sugar content exceeds 0.03% of dry matter. Potatoes destined for commercial chip production are carefully monitored to ensure reducing sugars are below this level.
An undesirable product of Maillard chemistry is acrylamide. This is a chemical that can be detected in tiny amounts in a range of fried or roasted foods, including potato chips, coffee, cocoa, chocolate and cereal-based bakery products, sweet biscuits and toasted bread (but not in steamed buns).
Acrylamide has been mentioned as a possible carcinogen, although according to Food Standards of Australia and New Zealand, the body that oversees the safety of our food, there is no direct evidence it causes cancer in humans. Acrylamide does not occur in raw foods or foods cooked by boiling or steaming.
Beyond the kitchen
Some aspects of the Maillard reaction have long been implicated in human ageing and health conditions.
Examples include loss of elasticity of connective tissue and the appearance dark spots on skin due to effects on collagen, cataract formation due to reactions with the lens protein crystallin, changes in neural proteins contributing to neuropathology and dementia, and glycation of haemoglobin due to elevated blood glucose levels in diabetes.
The importance of Maillard reactions in the kitchen and beyond is well established, even though these reactions are still not well understood more than a century after they were first described.
Nevertheless, we can take advantage of their benefits while continuing to learn about this fascinating area of chemistry.”
Week of July 18, 2005
Karen Collins, MS, RD, CDN American Institute for Cancer Research
Here we have a 11 y.o. article. Some new evidences were found since than but it shows us that people are still misinformed about this issue. To develop the Healthy Grill USA project we found more than 2000 studies starting in 1969.
“Many Americans still do not know that grilling can be unhealthy. The cancer risk from grilling, however, is real, but it changes dramatically with what you grill and how you do it.
The problem with traditional grilling comes from the combination of meat with intense heat. Whether you are using red meat, poultry or seafood, substances in the muscle proteins of these foods react under high heat to form carcinogenic compounds called heterocyclic amines (HCAs). HCAs can damage the DNA of our genes, beginning the process of cancer development.
Consumption of HCAs is mostly clearly linked to cancers of the colon and stomach. One study found that people who eat the most barbecued red meat (beef, pork and lamb) almost doubled their risk of colon polyps, compared to those who did not eat these foods. Colon polyps can develop into colon cancer. Some evidence also suggests that these carcinogenic compounds can travel through the bloodstream to other tissues. This would explain why HCAs could be a factor in breast cancer and other cancers.
A simple way to decrease formation of carcinogenic HCAs is to cook your meat at lower temperatures, like roasting it in the oven and stewing it. If you still want to grill, turn the gas down or wait for charcoal to become low-burning embers. By raising the grilling surface from the heat source, you can also reduce black char that can form on meat. This char has a high carcinogen content.
Pan-frying is another method of cooking that you should do at a lower temperature. Research shows that frying meat at a higher pan temperature, which saves only two minutes of cooking time, produces three times the HCA content of meat cooked at medium temperatures.
Two more ways to reduce HCAs when grilling are flipping meat every minute and marinating. Marinating can decrease HCA formation by up to 96 percent, although studies are still underway to determine which ingredients help the most.
To avoid a different class of cancer-causing compounds called polycyclic aromatic hydrocarbons (PAHs), grill leaner meat cuts that will drip less and cause fewer flare-ups and smoke. PAHs form in smoke and are deposited on the outside of meat.
Although it is a good idea to use an instant-read thermometer to be sure meat is thoroughly cooked, the further you cook meat past that point, the more HCAs will form. A higher consumption of well-done meat is linked with two to five times more colon cancer and two to three times more breast cancer. Risk of cancers of the stomach, pancreas and prostate may also increase.
Since the American Institute for Cancer Research (AICR) recommends limiting all red meat to no more than three ounces a day, another way to reduce your cancer risk when grilling is to change what you grill. Fish and marinated skinless chicken are both great on the grill, although HCAs can still form on them. If you still want to eat red meat, make kabobs. The small pieces of meat cook quickly, and you can add lots of vegetables.
The best choice for grilling, however, is vegetables and fruits, because they don’t form HCAs. These foods also supply a whole range of cancer-fighting nutrients and phytochemicals. In fact, the natural phytochemicals in vegetables stimulate enzymes that can convert HCAs to an inactive, stable form that is easily eliminated from the body. Even during barbecue season, your health will benefit by following AICR’s model of healthy eating called the New American Plate that makes vegetables, fruits, whole grains and beans the centerpieces of the meal.”
This article was published this week (December 5-11, 2016) on “The World Healthiest Foods” website managed by the George Mateljan Foundation, a no-profit foundation with no commercial interests or
advertising. “Our mission is to help you eat and cook the healthiest way for optimal health”.
“While grilling does create foods that have a unique flavor and texture, and grilling is pretty synonymous with summertime, we do have some concerns about it.
There are documented health risks associated with the char-broiling and gas grilling of foods. In general, these risks are associated with the formation of heterocyclic amines (HAs). Most HAs are well-documented carcinogens, and keeping their levels to a minimum in a diet can decrease our cancer risk. Here are the basic factors involved with HA formation in food:
- It is best to grill or broil on an area without a direct flame as the temperatures directly above or below the flame can reach as high as 500°F to 1000°F. HAs form most easily at high temperatures. Under 325°F, the formation of these compounds is very low. As temperatures increase above 400°F, the formation of HAs can increase by 700%-1000%. Gas and charcoal grilling often (but not always) involve higher temperatures.
- More HAs form when a food is in very close proximity to a heat source. Flame-grilling is perhaps the best example of a food coming into direct contact with a heat source. Less contact with the heating element (whatever heating element is used) lowers the formation of HAs. In deep fat frying, for example, where we might expect high HA formation, there is often very little HA creation due to relatively low temperatures and indirect exposure to the source of heat (although deep fat frying involves its own set of issues related to health concerns).
- The longer a food is exposed to high heat, the greater the HA formation. When a food like a hamburger is grilled for 10 minutes versus 6 minutes, for example, the HA levels in the hamburger may increase by 25-30%.
- The so-called “MPF” foods (meat, fish, and poultry) are more likely to form give rise to HA formation when prepared in the above fashion because HA formation requires the presence of amino acids (from protein) as well as the nitrogen-containing substances creatine or creatinine. Both of these substances are plentiful in most animal foods.
The principles of nutrient loss from charcoaled or gas-grilled foods are very similar to the principles of all cooking: the shorter the time of exposure to heat, and the lower the heat, the less the nutrient loss. Since this cooking method does not typically involve use of water, there can be less nutrient loss from this method than from boiling or simmering. However, minimal steaming of a food would typically requiring less total cooking time and for this reason result in decreased loss of nutrients.
As noted above, most of the research on HAs has been done on meat. Therefore, it is uncertain that the grilling of vegetables and fruits may have the same level of outcomes, notably because some of the phytonutrients found in vegetables, such as the sulforaphane in broccoli, have been found to reduce the carcinogenic effect of the HAs in research studies.
The bottom line: from a health perspective, we would choose other methods of preparing foods rather than grilling, yet if you want to enjoy grilled foods on occasion, given that the rest of your diet is healthy, it may not be so detrimental. If you do choose to grill foods and use an oil to coat them, we would suggest using an oil that has a high smoke point, such as avocado oil or high-oleic safflower oil to avoid the formation of oxidative damage to the oil itself. Additionally, there are certain antioxidant-containing foods, such as rosemary, citrus fruits and green tea, which have been found to reduce HA levels. Therefore, you could consider using these foods in marinades if you are looking for ways to reduce HA formation.”
- Acrylamide is a toxic molecule shown to increase cancer risk
- It forms during frying, baking or roasting foods rich in carbohydrates
- Chemistry professor Simon Cotton explores what the risks are
By Simon Cotton For The Conversation – Daily Mail UK
PUBLISHED: 12:05 EST, 15 August 2016 | UPDATED: 19:28 EST, 15 August 2016
“The reason we even know about acrylamide’s potential dangers are down to a railway tunnel.
Nearly 20 years ago, workers were building a tunnel through the Hallandsås ridge on the Bjäre peninsula in southern Sweden.
Cows nearby started to show strange symptoms, staggering around and in some cases collapsing and dying.
This prompted an investigation that showed that they had been drinking contaminated stream water and that the contamination was from a toxic molecule, acrylamide.
The construction workers had been using its polymer, polyacrylamide, as a crack sealant.
This was, in itself, quite safe.
But the polymer-forming reaction was incomplete, so some unreacted acrylamide was still present.
The workers were tested to see if they also had unsafe levels of acrylamide in their blood, with a second ‘control’ group of people who had no known exposure to industrial acrylamide used as a benchmark.
However, it turned out that the control group also had surprisingly high amounts of acrylamide in their blood.
At first it was thought that burgers might be the source.
Then high levels of acrylamide were found in potato products such as fried potatoes, as well as in coffee.
It then became clear that acrylamide formation was associated with carbohydrate-rich foods, rather than protein-rich ones, and with foods that had been heated above 120°C (250°F), that is food that has been fried, roasted or baked.
This was a new discovery, but acrylamide must always have been formed in this style of cooking, ever since cooking was invented.
Acrylamide is formed in reactions between the natural amino-acid asparagine and some (naturally-occurring) carbohydrates.
You don’t find acrylamide in uncooked or boiled food.
Dairy, meat or fish products are much less likely to contain acrylamide.
It doesn’t matter whether the food is ‘organic’ or not, it’s the type of food that counts.
Acrylamide is also formed when smoking tobacco.
A ‘golden rule’ has been suggested: cook food until it goes yellow, not brown or black.”
The commonly used spice and flavouring agent, rosemary, derived from the leaves of the plant Rosmarinus officinalis L., displays antioxidant properties in foods and in biological systems. Moreover, in animal models rosemary components were found to inhibit the initiation and tumour promotion phases of carcinogenesis. In this work, we studied the mechanisms by which rosemary components block initiation of carcinogenesis by the procarcinogen benzo[a]pyrene (B[a]P) in human bronchial epithelial cells (BEAS-2B). Whole rosemary extract (6 μg/ml) or an equivalent concentration of its most potent antioxidant constituents, carnosol or carnosic acid, inhibited DNA adduct formation by 80% after 6 h co-incubation with 1.5 μM B[a]P. Under similar conditions, cytochrome P450 (CYP) 1A1 mRNA expression was 50% lower in the presence of rosemary components, and CYP1A1 activity was inhibited 70–90%. The observed reduction of DNA adduct formation by rosemary components may mostly result from the inhibition of the activation of benzo[a]pyrene to its ultimate metabolites. Carnosol also affected expression of the phase II enzyme glutathione-S-transferase which is known to detoxify the proximate carcinogenic metabolite of B[a]P. Treatment of BEAS-2B cells with carnosol (1 μg/ml) for 24 h resulted in a 3- to 4-fold induction of GSTπ mRNA. Moreover, expression of a second important phase II enzyme, NAD(P)H: quinone reductase, was induced by carnosol in parallel with GSTπ. Therefore, rosemary components have the potential to decrease activation and increase detoxification of an important human carcinogen, identifying them as promising candidates for chemopreventive programs.
Cigarette smoking is causally associated with a large number of human cancers ( 1). Tobacco use is by far the most widespread link between exposure to known carcinogens and death from cancer and is therefore a model for understanding mechanisms of cancer induction. Benzo(a)pyrene (BP) is a highly carcinogenic polycyclic aromatic hydrocarbon (PAH) present in emission exhausts, in charbroiled food, and in small quantity of cigarette smoke ( 2– 5), typically <10 ng/cigarette ( 6). BP is 1 of >60 carcinogens in cigarette smoke that is involved in the etiology of lung cancer ( 7). It is metabolically activated into BP-7,8-diol-9,10-epoxide (BPDE), which reacts with DNA predominantly at the N2 position of guanine to produce primarily N2-guanine lesions [e.g., BPDE-N2-deoxyguanosine (BPDE-dG) adduct; ref. 8]. The presence of BPDE-DNA adducts in human tissues has been conclusively established ( 9) and BPDE-dG adduct concentrated exclusively in bronchial cells and thus implicated in the initiation of human lung cancer ( 10). Although considerable evidence implicates BP as important causative agent of smoking-related cancers, its role is clearly not exclusive.
This carcinogen is metabolized by phase I enzymes to a large number of metabolites, including phenols, arene oxides, quinones, dihydrodiols, and diol epoxides ( 11). An overview of BP metabolic way leading to the formation of (+)-anti-BPDE-dG adduct is presented in Fig. 1
Principal metabolic pathway and DNA binding of the carcinogen BP. BP is a tobacco carcinogen that may be converted in vivo enzymatically or by oxygen reactive species to yield DNA-reactive dihydrodiol epoxides. Stereoselective generation of the mutagenic (+)-anti-BPDE from (−)-BP-7,8-dihydrodiol is catalyzed by CYP-dependent monooxygenases (P450) or ROS. Subsequent reaction of this electrophilic intermediate with genomic DNA produces stable adduct between dihydrodiol epoxide and the exocyclic amino group of guanosine. This kind of DNA lesion may be converted into mutations within the following replication cycle unless repair of this adduct is produced.
Check complete article at http://cancerres.aacrjournals.org/content/66/24/11938
Published 15 December 2006 at Cancer Research Journal
American Association of Cancer Research
Knowing Grilling or Barbecuing generates Benzopyrenes you can use this article to understand the real issues found when you eat grilled food cooked under the traditional/conventional methods including Card-Broilers.
There is no sentence “there is no evidence”. knowing Benzopyrenes are related with cancer diseases and Grilling/Barbecuing also produce them it’s not difficult to associate.