Longer days and warmer weather have arrived – a time when we see outdoor grilling and BBQs as a summertime staple for preparing meals. This transition does, however, present some potential health challenges. Open flames of gas and charcoal can induce polycyclic aromatic hydrocarbons (PAHs) in cooked meat. PAHs, a group of highly hydrophobic and organic compounds are ubiquitous in the environment. PAHs are harmful to human health, and a number of them are carcinogenic, mutagenic, and genotoxic. 

Similarly, heterocyclic amines (HCAs) are a group of mutagenic compounds found in cooked meats, particularly well-done meats. Mutagenic— that is, they cause changes in DNA that may increase the risk of cancer. Natural components in meat, such as amino acids, creatine, and polysaccharide precursors, are converted to HCAs during high-temperature cooking. HCAs are known to cause cancer in laboratory animals. While HCAs are known mutagens, their carcinogenic potential in humans has not been established. Multiple studies, however, have reported HCAs to be associated with various cancers, including breast, prostate, colorectal, gastric, and pancreatic cancer. PhIP (2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine), one of the most abundant HCAs from cooked meat has potent estrogenic effects. Researchers have theorized that the estrogenic properties of PhIP influence metastatic potential.

Does what you grill affect these compounds?

The type of protein cooked can also affect the concentration of HCAs. It has been reported, for example, that chicken has more than 100 times the number of HCAs than salmon. London broiled steak had more than 600 times the amount of HCAs when compared to salmon. Fats dripping on the fire, particularly open flames of charcoal, induce excessive PAHs. While the total HCA amounts in wire barbecued samples were higher than stone barbecued samples, the total PAH amounts in stone barbecued samples were higher than those of wire barbecued samples. Surprisingly, the use of bourbon-soaked oak and cherry wood chips had inhibitory effects on both PAH and HCA contents in salmon.

Factors that enhance carcinogenesis when combined with HCAs include:

• High-fat diet

• Caffeine

Factors that inhibit carcinogenesis when combined with HCAs include:

• Docasohexaenoic acid (DHA) - an omega-3 fatty acid found in cold-water fish, DHA-enriched eggs, and breastmilk

• Conjugated linoleic acid (CLA) - a fatty acid found in meat and dairy

• Isoflavones - phytonutrients found in soy foods, such as edamame, tofu, and tempeh

• Diallyl sulfides - found in the allium family, such as garlic, onions, leeks, and shallots

• Green tea catechins

• Indole-3-carbinol - substance found in cruciferous vegetables, including arugula, broccoli, Brussels sprouts, cabbage, cauliflower, collard greens, horseradish, kale, kohlrabi, mustard greens, radishes, rutabaga, turnips/ turnip greens, and watercress

• Probiotics - beneficial bacteria naturally found in fermented foods, yogurt, kefir, kombucha, and apple cider vinegar

• Gamma-tocopherol - a form of vitamin E naturally found in walnuts, pecans, sesame seeds, pistachios, flax seeds, and pumpkin seeds

• Cloves & cinnamon

Improving the Safety Profile of Grilling

The most important variables contributing to the formation of HCAs are:

• Cooking temperature - greater than 300°F

• Cooking time - greater than 2 minutes

• Cooking method - frying, oven grilling/broiling, barbecuing

Charring of food, charcoal-broiled or smoked foods, contribute to PAHs. Research suggests the formation of PAHs is more affected by the change in temperature than of time. Hence, cooking animal protein at a lower temperature for a slightly longer period of time would be preferred in regards to PAH concentrations.

Meat can potentially be made “safer” to eat by being cooked in a way that does not lead to HCA formation.

• Choose lean, well-trimmed meats to grill.

• Using marinades significantly reduces the amount of HCAs.

• Brief microwave preheating substantially reduces HCA content of cooked meat. 

• Small portions require less time on the grill.

• Grill vegetables or meat alternatives that do not lead to the formation of HCAs or PAHs.

Summary 

Be mindful of how your food is prepared. Eat plants, and lots of them. If you opt for animal protein, consider salmon over red meat. Marinate your protein. Control the temperature and length of time exposed to the heat. Utilize components noted above to inhibit carcinogenesis – for example, serve your meal with broccoli and shallots topped with pumpkin seeds and a splash of apple cider vinegar. And, most definitely, enjoy your meal!