Grilling your food over an open flame can cause cancer.
Many different foods have been blamed for causing cancer over the years. Some people accuse red meat or processed meat. Others are sure sugar is to blame. Still others cite animal studies that conclude genetically modified foods are the culprit.
I’ve read several sources that say what we eat actually matters LESS than how we cook it. A quick internet search turned up many sources that claim cooking foods, especially meat, over an open flame could be the most concerning of all.
According to cancer.gov, heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs) are what we need to watch out for. HCAs are formed when meats are cooked at high temperatures while PAHs are formed when foods are exposed to smoke.
Well-done, grilled, pan-fried or barbecued meats that are cooked at temperatures above 300 degrees are likely to have more HCAs than meats that are baked, cooked slowly over low heat, or are less well-done.
When foods containing HCAs or PAHs are eaten, enzymes in the body start to break them down and make them capable of damaging DNA. This process is called bioactivaiton. Enzymes involved in bioactivation may vary among different people.
Cancer.gov sites animal studies that suggest HCAs and PAHs cause various types of cancers in rodents when fed in large amounts (thousands of times the amounts humans would typically consume). Associations have also been found between certain cancers and frequent consumption of meats cooked at high temperatures in large epidemiologic studies.
The World Cancer Research Fund and the American Institute for Cancer Research issued dietary guidelines recommending limited consumption of red, processed, and smoked meats. However, no recommendations were provided for HCA and PAH levels.
Nutritiouslife.com mimics these concerns. The site states that human studies haven’t been able to find strong cancer associations like the animal studies, but you might still want to err on the side of caution. The authors recommend removing burned or charred portions of meats because HCAs are only found there. Additionally, since smoke is often formed by fat dripping from the meat, they recommend using low-fat meats. Finally, they suggest that marinating meat helps lessen HCA formation due to antioxidants in herbs and spices.
A similar article in Men’s Health Magazine recommends putting foil over the grill to avoid too much smoke and eating lots of veggies to increase your antioxidants. Other articles, including one by the Washington Post, have similar advice. They state that grilling (even burning) vegetables does not pose the same risk as grilling meats.
Unlike most of the topics I research, there isn’t much debate over this one. The consensus is that meats cooked at high heats or over an open flame may cause cancer if you eat them often. However, I didn’t find any articles exaggerating the evidence. Instead, they suggest limiting these meats to around once a week and using simple strategies to decrease the risks. I’m still curious to see what the research says. Just how dangerous are these meats?
Peer reviewed research (Or click here
to skip to the discussion)
- A review and meta-analysis of prospective studies of red and processed meat, meat cooking methods, heme iron, heterocyclic amines and prostate cancer. (2015) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4687294/
This meta-analysis reviewed 19 different cohort studies and DID NOT reveal significant patterns of associations between red or processed meat and prostate cancer. Cooking methods were addressed in 5 of the 19 studies and again there was NO association between high temperature cooking and prostate cancer.
2. Are meat and heme iron intake associated with pancreatic cancer? Results from the NIH-AARP Diet and Health Cohort (2016) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4764390/
This cohort study reviewed dietary patterns of 322,846 participants over 10 years. They found significant associations between pancreatic cancer in men and red meat, meat cooked at high-temperature, grilled/barbequed meat, well/very well done meat, and heme iron from red meat. Surprisingly, they only found a significant association between pancreatic cancer in women and intake of white meat.
3. A prospective study of meat, cooking methods, meat mutagens, heme iron, and lung cancer risks. (2009) https://www.ncbi.nlm.nih.gov/pubmed/19369370
This study reviewed dietary patterns and cooking methods in 278,380 men and 189,596 women. There was a moderate association between red meat consumption and lung cancer. They proposed this might be explained by heme iron intake and high-temperature cooking.
4. Grilled, Barbecued, and Smoked Meat Intake and Survival Following Breast Cancer. (2017) https://www.ncbi.nlm.nih.gov/pubmed/28052933
This study followed 1508 women who were diagnosed with breast cancer in 1996 and 1997. 5 years later, 597 of the women had died, 237 from breast cancer related causes. Researchers found that women with continued high grilled/barbecued and smoked meat intake after diagnosis were 31% more likely to die of any cause. They also found that breast-cancer specific mortality was decreased among women with any pre- and post diagnosis intake of smoked poultry of fish. This suggests that all meats may not affect us equally. Smoked poultry or fish may be less harmful than other meats.
5. Meat intake, cooking methods, dietary carcinogens, and colorectal cancer risk: findings from the Colorectal Cancer Family Registry. (2015) https://www.ncbi.nlm.nih.gov/pubmed/25846122
This study reviewed diets and cooking methods for 3364 cases of colorectal cancer as well as several thousand unaffected family members and controls. The main finding was a positive association between pan-fired beef steak and colorectal cancer. The also found borderline significant associations with colorectal cancer for diets high in oven-broiled ribs. Surprisingly, they found an inverse association between colorectal cancer and grilled hamburgers and no association with total non-processed red meat or total processed meat. The authors noted that the associations were more prominent with a certain gene expression (MMR deficiency)
6. Meat-related compounds and colorectal cancer risk by anatomical subsite. (2013) https://www.ncbi.nlm.nih.gov/pubmed/23441608
This study compared the diets of 989 people with colorectal cancer and 1033 controls. Positive associations were found with processed meat and pan-fried red meat. However, inverse associations were found with poultry, even when grilled, well-done or charred. The authors noted that this was unexpected.
7. Grilled meat consumption and PhIP-DNA adducts in prostate carcinogenesis. (2001) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2132437/
This study concluded that reduction of grilled red meat (but not white meat) consumption may reduce prostate cancer risk.
8. How do you want your steak prepared? The impact of meat consumption and preparation on prostate cancer. (2012) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3469470/
This study analyzed the diets of 982 men with prostate cancer. They found associations with ground beef, processed meat, and well done meat. There was no association with rare or less cooked meat. The study only addressed red meat.
9. Impact of meat consumption, preparation, and mutagens on aggressive prostate cancer. (2011) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3223211/
This study included 470 cases of prostate cancer and 512 controls. Higher consumption of well-done ground beef or processed meats were associated with aggressive prostate cancer. In contrast, consumption of rare/medium cooked ground beef was not associated with aggressive prostate cancer.
10. Dietary Intake of Meat Cooking-Related Mutagens (HCAs) and Risk of Colorectal Adenoma and Cancer: A Systematic Review and Meta-Analysis. (2017) https://www.ncbi.nlm.nih.gov/pubmed/28524104
This meta-analysis reviewed 39 studies and concluded that “mutagenic compounds” (HCAs) formed during cooking of meat at high temperatures may be responsible for colorectal cancer.
11. Red meat-derived heterocyclic amines increase risk of colon cancer: a population-based case-control study. (2013) https://www.ncbi.nlm.nih.gov/pubmed/24168237
This study interviewed 1062 people with colon cancer and 1645 controls. They concluded that HCAs and PAHs from well-done red meat, but not white meat, was associated with colon cancer.
12. Dietary heterocyclic amines and cancer of the colon, rectum, bladder, and kidney: a population-based study. (1999) https://www.ncbi.nlm.nih.gov/pubmed/10073512
This study looked at diets of 553 controls, 352 cases of colon cancer, 249 cases of rectal cancer, 273 cases of bladder cancer, and 138 cases of kidney cancer. Researchers estimated average daily intake of HCAs to be 60-100 nanograms. Only intakes of above 1900 nanograms were associated with cancer. (7 of the cancer patients had intakes this high whereas none of the controls did.
What We Know and Don’t Know
Ok, so what does all this mean? Most of these articles seem to support the hypothesis that well-cooked meat causes cancer. On the surface, that appears to be true. But, after looking at all this data, I’m not convinced it’s something we should worry too much about.
Why? Well, for starters, most of the studies only found associations with red meat. With the exception of a weak association in one study, white meat and fish are off the hook. (pun).
Second, these are epidemiological and/or prospective cohort studies, NOT trusty randomized controlled trials. To review, a prospective cohort study follows a group of similar individuals over a long period of time to see what will happen with regards to a certain outcome (like cancer). Epidemiological studies look at large populations and try to find associations.
It is clear that certain cancers, especially colorectal and prostate cancers, are associated with high intakes of well-done red meat. However, it is possible that other factors that were not controlled for could be at play. Also, there were plenty of people in all of these studies that ate lower amounts of well-done meats and still got cancer. The associations reported were significant, but weak. There are probably other factors (like genetics) that more strongly contribute to your chances of getting cancer.
Conclusions and applications
Because well-controlled animal studies also show that red meats cooked at high temperatures may cause cancer, I wouldn’t completely disregard the weaker evidence from human studies.
However, I wouldn’t go out of my way to change my eating habits unless I was eating well-done red meat nearly every day. You would be better off paying attention to things like sugar intake and overall calories before worrying about how you should or shouldn’t cook your meat.
If I was in the habit of eating well-done burgers most days, I’d cycle them out with chicken or fish to minimize cancer risks and stay healthier overall.