Health Risks of Grilling Meats
Cooking meats or fish over flames or very high temperatures leads to the formation of carcinogens; improper storage or preparation can cause food-borne illness; and careless grilling can result in injury. We all love to grill during the summer but not all of us understand some of the dangers or potential downside.
When meat, poultry, or fish is cooked over flames or very high temperatures, muscle proteins react with the heat to form compounds called heterocyclic amines (HCAs). HCAs have been shown to cause cellular DNA changes that can lead to certain cancers. Other cancer-causing chemicals that may be found in meats prepared in this way include the polycyclic aromatic hydrocarbons (PAHs). Exposure to PAHs is also believed to be associated with the development of particular cancers. Studies have linked the consumption of grilled meat to an increased risk of colon, prostate, pancreatic, stomach, and breast cancers, especially if the meat is cooked until it is well done.
HCAs are formed when amino acids, sugars, and creatine react at high temperatures. They 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 an open fire drip onto the fire, igniting and producing smoke. The smoke contains PAHs, and when it rises, it can deposit these chemicals onto the surface of the meat. PAHs can be found in other charred foods besides meat, and they can also be formed during other food preparation processes, such as smoking of meats. In addition, they can be found in cigarette smoke and car exhaust fumes. The formation of HCAs and PAHs in cooked meats varies according to the type of meat being cooked, the cooking method employed, and the level of “doneness” reached (i.e., rare, medium, or well done). Regardless of the type of meat, however, meats that are cooked at high temperatures, especially above 300°F (as in grilling or pan-frying), or that are cooked for a long time tend to form more HCAs. For example, well-done, grilled, and barbecued chicken and steak all have high concentrations of HCAs. Cooking methods that expose meat to smoke or charring contribute to PAH formation.
Even though no specific guidelines for HCA/PAH consumption exist, there are several modifications that concerned individuals can make to their cooking approach so as to reduce their exposure to these compounds:
- Avoid direct exposure of meat to an open flame or a hot metal surface, and avoid prolonged cooking times (especially at high temperatures) – This will help decrease formation of HCAs and PAHs
- Cook the meat at a lower temperature (<325°F) for a longer time by turning the gas down or letting the charcoal burn down to the embers
- Use a microwave oven to cook meat before exposing it to high temperatures so as to shorten the time that the meat must be in contact with high heat to finish cooking – 2 minutes of microwave cooking before grilling may reduce HCAs by as much as 90%
- After microwaving, pat the meat dry so that there is less juice to drip into the grill
- Continuously turn meat that is being cooked over a high heat source – This can substantially reduce HCA formation in comparison with leaving the meat on the heat source for prolonged periods without flipping it
- Remove charred portions of meat, and refrain from using gravy made from meat drippings – These measures can also significantly reduce exposure to both HCAs and PAHs.
Other grilling tips for lowering exposure to HCAs and PAHs are as follows:
- Keep it lean – Start with lean meat, and cut off all the skin and visible fat before you grill; this not only will make the meat more nutritious but also will limit flareups that can char the meat
- Marinate first – Research has found that marinating chicken breasts in a combination of cider vinegar, olive oil, lemon juice, and spices can reduce HCA formation by as much as 99%
- Spice it up – According to one study, rolling meat in spices like rosemary and turmeric before cooking can cut HCA production by more than 40%
- Shield the meat – Put tin foil under the meat and poke a few holes in it; this will reduce the amount of juice that drips into the grill and will allow less smoke to reach the meat
- Increase the distance from the heat source – To lower the amount of heat and char on the meat, raise the grilling surface, and move the charcoal briquettes to the sides of the grill
- Add vegetables to the grill – Because vegetables do not form HCAs and are lower in fat and calories than meat is, it is beneficial to use more of them and less meat
- Keep it clean – After each use, clean the grill thoroughly to get rid of any charred food that is stuck to the surface
- Control portion size – Grill smaller portions of meat, poultry, and fish, which will cook faster and thus will spend less time on the grill
Besides the formation of HCAs and PAHs, the summer grilling season is also associated with the broader risks posed by high consumption of red and processed meats. (The term red meat is generally understood as referring to beef, pork, and lamb, though some studies include all processed meats, such as bacon, sausage, hot dogs, and cold cuts, in their definition, regardless of their animal origin.) During grilling season, many Americans end up eating large quantities of very-high-fat meats and sausages, thereby adding yet more calories, fat, saturated fat, and cholesterol to diets that may already include large amounts of these components. Red meat and processed meat have been found to be associated with an increased risk of colorectal cancer, and evidence also suggests that they are associated with other cancers, such as prostate cancer. More research is needed to understand how these meats influence cancer risk.
Ways of mitigating the adverse effects of high meat consumption include the following:
- Look for meats raised without synthetic hormones – Although the United States Department of Agriculture (USDA) prohibits the use of hormones in the raising of hogs or poultry in the United States, it does allow the use of a number of hormones in the raising of cattle; beef carrying the label “no hormones administered” is considered to be free from any added hormones over the lifetime of the animal
- Buy organic – Try to buy certified organic pork, beef, and poultry from animals raised without use of antibiotics, genetic engineering, irradiation, sewage sludge, and artificial ingredients
- Look for grass-fed beef – Beef from grass-fed cattle is leaner, lower in fat and calories, and higher in vitamin E and antioxidants than beef from corn-fed cattle; it is also lower in saturated fats and higher in omega-3 fats
- Consume smaller quantities – Clearly, the easiest and most affordable way of reducing exposure to the contaminants that may be in meat and poultry is to eat less of those foods; this can be done by making some meals meat-free, by consuming smaller portions when meat is eaten, or both
In addition to the aforementioned risks, meats that are undercooked or improperly prepared can give rise to food poisoning. Each year, 76 million Americans are diagnosed with food poisoning, most often from eating undercooked meat, poultry, and other animal products. Bacteria such as Escherichia coli and Salmonella species are regular residents in chicken, beef, and meats. If meat is not cooked to a temperature high enough to kill these bacteria, the organisms can be transported to the intestinal tract and cause symptoms such as vomiting, stomach cramps, and diarrhea.
The following tips for purchasing meat and poultry can help minimize the risk:
- Check foods on the recall list when planning a grill fest
- When shopping, buy meat and poultry last, right before checkout
- Separate raw meat and poultry from other food in the shopping cart; place packages of raw meat and poultry into individual plastic bags
After purchase of meat, poultry, or seafood, appropriate transport and storage will help minimize the chances of food poisoning:
- Plan to drive directly home from the grocery store, and consider bringing a cooler with ice for perishable foods (which should always be refrigerated within 2 hours—or within 1 hour if the temperature is above 90°F)
- At home, place meat and poultry in the refrigerator immediately; freeze any poultry and ground meat that will not be used in 1-2 days, and freeze other meat within 4-5 days
- If meat or poultry has been frozen, thaw it completely before grilling so that it cooks more evenly; use the refrigerator for slow and safe thawing, or thaw sealed packages in cold water; for quicker thawing, defrost the food in the microwave if it will be placed on the grill immediately afterward
- Marinate food in the refrigerator, not on the counter; poultry and cubed meat or stew meat can be marinated for as long as 2 days, whereas beef, veal, pork, and lamb roasts, chops, and steaks may be marinated for as long as 5 days
- If some portion of a marinade is to be used as a sauce on the cooked food, reserve it in a separate cup or other container before placing raw meat or poultry in the remaining portion of the marinade; however, if the marinade used on raw meat or poultry is to be reused, boil it first to destroy any harmful bacteria
Also important for preventing food poisoning is careful preparation. The following food safety tips will help ensure that grilled meat does not make diners sick:
- Separate foods – To avoid bacterial cross-contamination, keep raw meat away from fruits, vegetables, and any other foods that will be eaten without being cooked; cut raw meats on a different surface from the one(s) used for other foods, then wash every cutting board, plate, and utensil the raw meat touched with hot water and soap; always use new serving plates and utensils for cooked food
- Clean up – Wash hands with warm water and soap for at least 20 seconds before preparing food and after handling raw meat, and ask anyone else who will be handling food to do the same
- Keep it cold – Store meat and poultry in the refrigerator until it is time to grill it; if any meat is left over from grilling, either keep it warm (≥140°F) or put it in the refrigerator within 2 hours (within 1 hour if the temperature outside is higher than 90°F)
Proper cooking is essential as well. All meat, poultry, and fish must be cooked to an appropriate temperature. Color is not a reliable guide to whether something is cooked or not. Meat and poultry may brown quickly and appear done even when it is not. To be certain that meat is cooked thoroughly, insert a food thermometer into the thickest part of the meat, and keep cooking until it reaches the following temperatures:
- Whole chicken or turkey – 165°F
- Chicken or turkey breasts (boneless) – 165°F
- Ground chicken or turkey – 165°F
- Hamburgers, ground beef – 160°F
- Beef roasts or steaks – Medium rare, 145°F; medium, 160°F; well done, 170°F
- Pork – 160°F
- Fish – 145°F
- Hot dogs – 165°F or steaming hot
Once the food is cooked, the following considerations are helpful:
- When carrying food to another location, use an insulated cooler with sufficient ice or ice packs to keep the food at 40°F or below; pack food right from the refrigerator into the cooler immediately before leaving home, placing beverages in one cooler and perishables in a separate cooler
- When using a cooler, keep it out of the direct sun by placing it in the shade or under shelter; avoid opening the lid too often, which lets cold air out and warm air in
- When planning to eat away from home, find out if there is a source of clean water; if not, bring water for preparation and cleaning, or pack clean cloths and moist towelettes for cleaning surfaces and hands
- When not eating food, cover it to keep insects from landing on it and contaminating it with the microbes on their feet and bodies; throw away any piece of food on which an insect has crawled
- When reheating fully cooked meats such as hot dogs, grill until the meat reaches 165°F or is steaming hot
- Keep cooked meats hot by setting them to the side of the grill rack—not directly over the coals, where they could overcook; at home, cooked meat can be kept hot in an oven set at ~200°F, in a chafing dish or slow cooker, or on a warming tray
Proper treatment of meat, poultry, and seafood so as to avoid food poisoning or food-borne illness can be summarized in the four basic food safety steps, as follows:
- CLEAN – Wash hands and food preparation surfaces often
- SEPARATE – Avoid cross-contamination; when handling raw meat, poultry, seafood, and eggs, keep these foods and their juices away from ready-to-eat foods
- COOK – Cook to proper temperature
- CHILL – Refrigerate food quickly; at room temperature, bacteria in food can double every 20 minutes
Raw meat may contain bacteria (eg, E coli, Salmonella, and Listeria) or parasites. Thorough cooking destroys these harmful organisms, but meat can become contaminated again if it is not handled and stored properly. Chicken and other poultry may also contain harmful bacteria (eg, Salmonella,Listeria, and Campylobacter). These bacteria are not removed by washing; they can be killed only by cooking to the proper temperature. Raw seafood too may contain bacteria that can be destroyed only by cooking; some seafood may also contain toxins (eg, mercury) that may be harmful to young children or fetuses.
Some of the risks associated with outdoor cooking arise not from the foods being cooked but from the tools used to cook them. Each year, an average of 8900 home fires are caused by grilling, and close to half of all injuries involving grills are due to thermal burns. In nearly one fifth (19%) of all grill structure fires, failure to clean the grill was the main factor contributing to the fire. In 17%, a flammable object or substance was too close to the grill. Leaks or breaks were the primary contributing factor in 11% of grill structure fires and 23% of outside and unclassified grill fires. Overall, gas grills contribute to a higher number of home fires than their charcoal counterparts.
General grilling tips include the following:
- Never use propane or charcoal grills indoors
- Place the grill well away from the home and deck railings, and make sure that it is not under eaves or overhanging branches
- Keep children and pets away from the grill area
- Keep the grill clean by removing grease or fat buildup from the grills and from trays below the grill
- Never leave the grill unattended
- Wire bristles from grill-cleaning brushes may dislodge and become stuck into food cooked on the grill. Internal injuries have been reported. If using a wire bristle brush, thoroughly inspect the grill’s surface before cooking.
The following tips apply to propane grills:
- Each year, before using the grill for the first time, check the gas tank hose for leaks by applying a light soap-and-water solution to the hose; a propane leak will release bubbles
- If a gas leak is smelled or detected with the soapy bubble test and there is no flame, turn off both the gas tank and the grill; if the leak stops, have the grill serviced by a professional before using it again, but if the leak does not stop, call the fire department
- If gas can be smelled during cooking, immediately step away from the grill and call the fire department; do not move the grill; if the flame goes out, turn the grill and gas off and wait at least 5 minutes before relighting it
The following tips apply to charcoal grills:
- If using a starter fluid, use only charcoal starter fluid; never add charcoal fluid or any other flammable liquids to the fire
- Keep charcoal fluid out of the reach of children and away from heat sources.
- If using an electric charcoal starter, have an appropriately rated extension cord available
- When finished with grilling, allow the coals to cool completely before disposing of them in a metal container.
Enjoy safe and healthy grilling!
Paul R. Block, MD, FACP, FCCP
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