When meat is barbecued may be formed many harmful components, as heterocyclic amines (HCA) and polycyclic aromatic hydrocarbons (PAH). Beef contains more PAH than pork and chicken, and HCA concentrations is higher in meat with darker surface. (http://www.sciencedirect.com/science/article/abs/pii/S0309174012002719?via%3Dihub)
They are formed when muscle meat (beef, pork, fish, poultry) is cooked with high temperature as frying or grilling over an open flame. In laboratory experiments, HCAs and PAHs have been found to be mutagenic—that is, they cause changes in DNA that may increase the risk of cancer.
HCA and PAH
- HCAs are formed when amino acids (the building blocks of proteins), sugars, and creatine or creatinine(substances found in muscle) react at high temperatures. HCAs are not found in significant amounts in foods other than meat cooked at high temperatures.
- PAHs are formed when fat and juices from meat grilled directly over a heated surface or open fire drip onto the surface or fire, causing flames and smoke. The smoke contains PAHs that then adhere to the surface of the meat. PAHs can be found in other smoked foods, as well as in cigarette smoke and car exhaust fumes. meats cooked at high temperatures, especially above 300 ºF (as in grilling or pan frying), or that are cooked for a long time tend to form more HCAs. For example, well-done, grilled, or barbecued chicken and steak all have high concentrations of HCAs. Cooking methods that expose meat to smoke contribute to PAH formation. Wood smoke, which is used to cook and preserve foods, contains a large number of PAHs, which also contaminate the foods upon contact.
It can be difficult to determine the exact level of HCA and/or PAH exposure a person gets from cooked meats. Also, people may have been exposed to PAHs from other environmental sources, not just food.
Once you eat the meat, the HCAs are metabolized in your body by specific enzymes.
Researchers have found that this group of enzymes has varying degrees of activity in different people. This may be relevant to how much or little the HCAs increase your specific risk of cancer.
The amount of HCAs appear to be dependent on the type of meat, how well-done it is cooked and the temperature used to cook the meat.
To date, there have been more than 10 different HCAs identified from cooking meat and fish. When HCAs have been fed to rodents they developed cancer in multiple different organs, including the colon, breast and prostate.
It was found how grilled, barbecued and smoked meat intake may increase the risk of breast cancer and mortality after breast cancer.
Annual intake of smoked beef/lamb/pork was positively associated with all-cause and breast cancer–specific mortality.
Smoked beef/lamb/pork intake was also positively associated with all-cause and breast cancer mortality, with risk of mortality highest among women who reported high prediagnosis and low postdiagnosis intake.
Risk of breast cancer–specific mortality was inversely associated with any pre- and postdiagnosis intake of smoked poultry/fish.
Although we could not definitively rule out chance as an explanation for some of our findings, a link between dietary sources of PAH and breast cancer prognosis is biologically plausible and epidemiologically consistent. First, these foods have been previously associated with increased risk of breast cancer incidence; effect estimates range from 1.5 to 2.2 when comparing the highest to the lowest quantiles of intake of well-done meat. Second, dietary PAH exposures are hypothesized to be etiologically related to breast carcinogenesis as PAHs are known to form DNA adducts, which can cause mutations during DNA replication and may alter promoter methylation or promoter binding, leading to inheritable abnormal gene expression, early steps in carcinogenesis. Third, PAHs are also likely to influence breast cancer development and prognosis through endocrine disruption. Furthermore, higher fat content may also result in the formation of more PAHs. However, we did not observe the same elevated risk of mortality among women with continued postdiagnosis high intake and when we examined at-diagnosis intake of these meats cooked by grilling/barbecuing.
The lack of association between mortality and intake of grilled/barbecued beef/lamb/pork may be due to method of preparation:
- Marinating meat before grilling, as is often done, may inhibit the formation of PAHs.
- Our finding of an inverse association between smoked poultry/fish intake and mortality could also be related to the different fat composition of these meats. Moreover, it has been hypothesized that the amino acid content of white meat supports proper immune system function, while intake of fish, a source of omega-3 polyunsaturated fatty acids, could improve survival by reducing pro-inflammatory derivatives. Nonetheless, we did not observe reductions in mortality risk associated with the intake of grilled/barbecued poultry/fish intake.
The results of our study indicate that grilled/barbecued and, particularly, smoked meat consumed prior to and after breast cancer diagnosis may influence survival. This study, with confirmation by future studies, may help to identify modifiable prognostic indicators for the more than 3 million women who are survivors of breast cancer
Risk of these carcinogens forming is higher from red and processed meats – like hamburgers and hot dogs. Smoke or charring also contributes to the formation of PAHs.
Evidence is clear that diets high in red and processed meats, contribute to an increased risk of colorectal cancer. Based on the evidence, AICR recommends limiting red meat to 18 ounces of cooked meat per week and staying away from hot dogs or other processed meats.
Guide to Safe Grilling
While there does exist limited, but suggestive evidence that compounds produced in meat through the grilling process (HCAs) factor in human cancer, AICR has determined that top priority should be what you choose to cook, not how you cook it. Follow these guidelines for healthy grilling:
- Marinate: Studies have suggested that marinating your meat before grilling can decrease the formation of HCAs. Scientists theorize that the antioxidants in these marinades block HCAs from forming
- Pre Cook: If you are grilling larger cuts, you can reduce the time your meat is exposed to the flames by partially cooking it in a microwave, oven or stove first. Immediately place the partially cooked meat on the preheated grill. This helps keep your meat safe from bacteria and other food pathogens that can cause illness.
- Lean Cuts: Trimming the fat off your meat can reduce flare-ups and charring. Cook your meat in the center of the grill and make sure to flip frequently.
- Mix It Up: Cutting meat into smaller portions and mixing with veggies can help shorten cooking time. Need some inspiration?
- Go Green: Grilling vegetables and fruits produces no HCAs and plant-based foods are actually associated with lower cancer risk.
An anticancer diet would have:
• adequate, but not excessive calories,
• 10 or more servings of vegetables a day, including cruciferous and allium vegetables; vegetable juice could meet part of this goal,
• 4 or more servings of fruits a day,
• high in fiber,
• no refined sugar,
• no refined flour,
• low in total fat, but containing necessary essential fatty acids,
• no red meat,
• a balanced ratio of omega 3 and omega 6 fats and would include DHA,
• flax seed as a source of phytoestrogens,
• supplemented with ~200 μg/day selenium,
• supplemented with 1,000 μg/day methylcobalamin (B-12),
• very rich in folic acid (from dark green vegetables),
• adequate sunshine to get vitamin D, or use 1,000 IU/day supplement,
• very rich in antioxidants and phytochemicals from fruits and vegetables, including α-carotene, β-carotene, β-cryptoxanthin, vitamin C (from foods), vitamin E (from foods),
• very rich in chlorophyll,
• supplemented with beneficial probiotics,
• supplemented with oral enzymes
As reviewed above, reductions of 60 percent in breast cancer rates have already been seen in human diet studies, and a 71 percent reduction in colon cancer for men without the known modifiable risk factors. These reductions are without taking into account many of the other factors considered in this review, such as markedly increased fruit and vegetable intake, balanced omega 3 and 6 fats, vitamin D, reduced sugar intake, probiotics, and enzymes – factors which all are likely to have an impact on cancer. Certainly cancer prevention would be possible, and cancer reversal in some cases is quite likely.