The Potential Risks and Evidence
The key concern with cooking meats and fish at high temperatures (whether grilled, broiled, fried or seared) is the accelerated conversion of proteins into possible carcinogenic – cancer causing – compounds. These are known as HCA's (heterocyclic amines) and PAHs (polycyclic aromatic hydrocarbons).
Numerous experiments and studies on both animals (ref. 1) and humans (ref. 2) show how HCAs and PAHs are mutagenic - that is, they cause changes in DNA which may increase the risk of cancer.
Even charring vegetables on the grill can create different carcinogens such as acrylamide, which appears to be a cancer-causing and potentially neurotoxic chemical (ref. 3).
However, I suggest that we need to be cautious about such findings. Here’s why.
How Reliable is this Evidence?
As studies published in PubMed (ref. 4) reveal, HCAs and PAHs become capable of damaging DNA only after they are metabolized by specific enzymes in the body, a process called “bioactivation.”
In other words, the individual’s specific biology and cellular terrain will greatly influence whether these potential carcinogenic compounds contribute to causing cancer.
Also, many of the human studies were epidemiological. They mainly used detailed questionnaires to examine participants’ meat consumption and meat cooking methods to estimate HCA and PAH exposures.
I ask: can one really make valid conclusions based primarily on self-reported questionnaires?
Indeed, by their very nature, epidemiological studies can never prove causation. That is, they cannot prove that a specific risk factor actually causes the disease being studied. Epidemiological evidence can only show that this risk factor is associated (correlated) with a higher incidence of disease in the population exposed to that risk factor. The higher the correlation the more valid the association, but it cannot prove the causation.
So to properly understand the relationship between the consumption of HCAs and PAHs and cancer risk in humans, more robust clinical trials need to be conducted. These are indeed being initiated by US and European researchers (ref. 5)
As the investigation continues, how can one enjoy grilling and barbequing while minimising the potential health risks?
Safe Grilling + Barbequing Tips
It looks like Mum and Dad certainly knew a thing or two when it came to healthy barbequing! These are the tips they would recommend:
1. Counteract the effect of HCAs and PAHs by loading up on herbs and spices: Marinating meats/fish for hours beforehand in liquid mixtures containing herbs/spices can dramatically reduce any carcinogens that normally would form on grilled meat. The antioxidants in rosemary and thyme from a marinade were specifically cited in a study (ref. 6) as being powerful inhibitors of HCA formation when grilling meats. It was also noted that other spices such as garlic, ginger, turmeric and others can help to prevent HCA formation, so use a variety and slather on the marinade! As an added bonus, marinated meat tastes better and cooks faster.
2. Use lean, ideally organic meats/fish :When fat from the meats drip down into the coals or fire they may generate a carcenoginic smoke - PAH - polycyclic aromatic hydrocarbons which get deposited on food. This is minimized when you use leaner cuts of meat/fish.
3. Don’t overcook : The more that meat/fish is cooked, the higher the concentration of potentially carcinogenic HCA’s, so rare, medium-rare, or medium are healthier choices than well-done. If you are not too fond of the rare state, use a meat thermometer and stop cooking when it shows the right temperature (ref. 7).
The use of marinades and meat tenderisers also helps to prevent over cooking. A store bought meat tenderiser will typically have either papain (enzyme from papaya) or bromelain (enzyme from pineapple), salt and a host of other preservatives. I use a home made papaya based tenderiser with all natural herbs and spices + red wine! Remember the greener the papaya, the more papain power!
Also if you cut the meat/fish into smaller pieces, the cooking time will be shorter
4. Precook:This is especially useful for meats that have bone in them like chicken drumsticks thighs etc. Half cooking the meat in a stove top or oven and then popping on the grill will greatly minimize formation of HCA’s since less cooking time is required. This will also ensure evenly cooked meats.
5. Use the grill packet method: Wrapping meats, fish, and veggies in a foil packet cooks evenly, seals in flavour and minimizes formation of HCA’s. Using a grill basket does the same. I always use this method for fruits and veggies to prevent them from drying out and getting charred.
6. Clean grill: Clean the grill in between uses. Removing old gunk will reduce smoke, quicken cooking time and reduce HCA formation. Cleaning and scrubbing the grill will also make the food taste better.
7. Fire Safety:Know how to control and extinguish your fire!
I hope that these tips will help you enjoy healthy and happy grilling and barbequing. If you have any of your own, please do share them for all of us to savour!
1. Animal experiments showing how HCAs and PAHs are mutagenic http://www.ncbi.nlm.nih.gov/pubmed/15072585
2. Human experiments showing how HCAs and PAHs are mutagenic and may be carcenoginic:
3. Acrylamide appears to be a carcenoginic and potentially neurotoxic chemical http://pubs.acs.org/doi/abs/10.1021/jf020302f
4. PubMed studies showing the ‘bioactivation’ process
5. The following clinical trials on HCAs, PAHs are underway:
- the NIH-AARP Diet and Health Study http://www.ncbi.nlm.nih.gov/pubmed/19165862
- the American Cancer Society’s Cancer Prevention Study II http://www.ncbi.nlm.nih.gov/pubmed/16492907
- the Multiethnic Cohort http://www.ncbi.nlm.nih.gov/pubmed/19549810
- the European Prospective Investigation into Cancer and Nutrition (EPIC) study http://www.ncbi.nlm.nih.gov/pubmed/18309547
6. Benefits of marinading http://www.ncbi.nlm.nih.gov/pubmed/19241593
7. Here’s a list of safe cooking temperatures http://www.foodsafety.gov/keep/charts/mintemp.html