One of my friends, who lives in the Pacific Northwest emailed me last week to ask if I knew of any grills that would be less likely to create cancer-causing byproducts and what I know about this issue.
I had read in Debra Lynn Dadd’s book, Home Safe Home: Creating a Healthy Come Environment by Reducing Exposure to Toxic Household Products (page 310), that something about grilling made it more risky than broiling:
"For some unexplained reason, broiling with a gas flame or electric coil above the meat produces no benzo(a)pyrene.” Her conclusion was “So slather on the barbecue sauce and stick your meats under the broiler."
She mentioned that “University of Hawaii researchers have found you can reduce the danger of carcinogens in grilled meat by eating lots of green vegetables---the chlorophyll in vegetables binds with the carcinogens during digestion, limiting their absorption."
Photo right: Rachel Albert, Copyright© 2008.
The linkI knew that the association between grilled foods and cancer is related to HCAs (heterocyclic amines) and benzo(a)pyrene. Scientists believe that cooking temp, type of food, and fat content affect the amount of these compounds formed during grilling. Grilling
(aka barbecuing) fatty foods at the highest temps and closer to the flame produces more of these compounds than does lower temperatures or cooking food farther from the flame. There is also evidence that cooking meat to well done produces more cancer producing compounds than cooking it to rare or medium-rare.
These things I knew, but I wanted to get a second opinion and additional information from someone I knew had done more research into this than I had. I wanted to know how accurate this information was. I wanted to know how risky eating grilled meat was relative to other dietary practices and what we could do to minimize the risks when we do grill.
For answers to these and other questions I consulted with my colleague
Don Matesz, a nutritionist, herbalist, licensed acupuncturist,
paleo and primal diet expert, and adjunct nutrition professor at Southwest College of Naturopathic Medicine (SCNM) and Southwest Institute of Healing Arts (SWIHA) in Tempe, AZ. Don was also my co-author who collected and synthesized all the nutritional information for the award-winning book we co-wrote,
The Garden of Eating: A Produce-Dominated Diet & Cookbook (Planetary Press 2004).
The questions below are mine. The answers are Don’s.
Q: How risky is grilling?A: First, I put this in evolutionary perspective. Neither prehistoric people nor contemporary hunter-gatherers had equipment for grilling. Paleo people used baking, roasting, steaming, and boiling, not grilling. This means we have not had any time to adapt to the by-products of grilling.
Photo right: Rachel Albert, Copyright© 2009.
I think that we have good evidence that HCAs (heterocyclic amines) produced in meat cooked at high temperatures are carcinogenic, and several studies have found them in higher concentrations in cancerous tissues of humans: see
this study and
this one.
The epidemiological evidence also implicates grilling.
Click here to learn more. The relative risks reported range from 2 to 5 times, which makes these findings significant.
Q: Do you think it's really risky to eat grilled meats?A: Yes, if you do it frequently and especially if you grill to well-done.
Q: Do you think people should limit or avoid consuming grilled meats? A: If they want to avoid unnecessary exposure to carcinogens, I advise them to avoid eating grilled food as a general rule. I think you can have eat grilled food occasionally without concern, but eating it daily presents an unnecessary risk.
Q: I’ve read that marinating meat, fish and poultry in citrus juice or vinegar with herbs or herbs and spices, particularly rosemary, oregano and garlic reduces the production of HCAs. According to this study, the polyphenol antioxidants and other compounds in herbs and spices block production of cancer causing compounds. What do you know about this?
A: In that study, the Caribbean marinade produced the greatest decrease in the total HCA content (88%), followed by the herb (72%) and Southwest (57%). So the effects clearly and markedly depend on the ingredients in the marinade. Still, none of them eliminated the HCA production.
In addition, some research actually shows increased levels of some carcinogens when rosemary is added to grilled foods. For example,
this study found that "rosemary extracts (2%, 5%, 10% and 15%) apparently enhanced the total amount of HCAs measured in beef Shawerma."
Photo right: Rachel
Albert, Copyright© 2009.
Since the research appears inconsistent, effects are highly dependent on marinade ingredients, and we only know to look for the carcinogens we already know about, I don’t feel very confident that using marinades reduces the risks of grilling reliably enough to put it into the “safe for regular use” category.
Q: How risky is ingestion of grilled meats relative to other foods and dietary factors? If people are eating a whole foods diet, particularly a paleo or primal diet, is the risk of eating grilled meats that significant?
A: Grilling produces carcinogens that initiate cancer. Other dietary factors like vegetable oils and refined carbohydrates provide conditions that suppress immune function and fuel cancer growth. Both are risky behaviors. One can even argue that grilled food does not belong in a paleo/primal diet since paleo people could not grill foods and certainly did not use Caribbean marinade. Given that, I maintain that eating grilled meats regularly presents a significant deviation from a paleo/primal diet and the evidence indicates that it presents a significant risk.
Q: So if people do use oil in marinades, am I right that the best choices would be oils rich in monounsaturated fatty acids, such as olive or avocado oil and that people should avoid consuming vegetable oils (at any temperature), including corn, canola, safflower, canola, cottonseed, peanut, Wesson, Mazola, or anything labeled "vegetable" oil because they are rich in PUFAs (polyunsaturated oils) and are very unstable and easily damaged by light, oxygen, and especially heat. Is that right?Photo right: Rachel Albert, Copyright© 2009.
A: Well, I would definitely rank primarily monounsaturated oils like olive and avocado as better for this application than corn, etc., but they still sustain damage by exposure to high heat. I think the best marinade would contain no oils, or instead use a rub containing a primarily saturated fat like coconut oil or butter.
Q: Do you think the link between grilled meat and cancer is a distraction from other more risky dietary choices/behaviors, such as eating a high-sugar, high-carbohydrate diet, and consuming liberal amounts of polyunsaturated vegetable oils? A: No. The scientists who study this don’t do it to distract anyone from other issues. In fact, I think too few people understand the risks of grilling. This may especially apply to novice paleo dieters, who might not know of any way to prepare meats other than grilling.
Q: I’ve read that the association between grilling and cancer applies to meat but not vegetables and that grilled vegetables and fruits are safe to eat because they don’t produce carcinogens. Do you think that’s correct?A: No, I don’t. High heat treatment of carbohydrates can produce carcinogens, and vegetables and fruits also contain small amounts of protein and fat that could get converted to carcinogens when grilled. Plus, people often coat the vegetables with oils before grilling, leading to formation of toxic lipid by-products. Finally, grilling vegetables and fruits usually produces some degree of crust, which contains toxic materials.
Q: I’ve read that when grilling marbled or fatty meat or poultry with the skin on, if you place a drip pan under the meat this will prevent flare ups of fatty juices and the production of HCAs. If you prevent meat juices from hitting the coals or gas and rising up through the meat, then do you think it’s safe to grill more often (provided you also cook the meat rare or medium rare and eat it with at least twice as much vegetables or vegetables and fruit)?Photo right: Stacy Maxwell, copyright 2006.
A: Yes, I agree. The majority of carcinogens get produced when juices hit the flames, which converts components of the juices into aromatic compounds that then get lodged in the meat, so a drip pan will reduce this effect.
Q: What do you think people can realistically do to reduce their risk of developing diet-related cancers?
A: I think people can risk the risk of developing diet related cancers by avoiding these things:
- Cooking techniques with high temperatures for long times with direct exposure to flames.
- Processed vegetable oils.
- Refined sugars.
- Cereal grains, particularly gluten-containing grains (wheat, barley, rye, and spelt, etc.), and cereal grain products cooked at high temperatures (e.g., dry cereals, crackers, puffed and extruded snack foods, French fries, potato chips, pizza, crusty Arisan breads, and deep fried grain products).
People can also reduce the risks of developing diet related diseases by eating these foods:
- Vegetables and herbs
- Fruits
- Nuts
- Meats cooked briefly with gentle heat (baked, roasted, steamed, boiled, stir-fried)
Q: I’ve been seeing a lot more articles about the importance of maintaining adequate vitamin D levels for preventing cancer. You wrote about this in The Garden of Eating but at the time the book came out the issue wasn’t given much press. What are your thoughts about this now?
A: I still recommend that everyone get adequate sun exposure or take a vitamin D supplement to maintain healthy levels of vitamin D (40-60ng/mL). You can get tested inexpensively through
Grassroots Health. Q: How much meat do Americans really eat relative to grains and starchy foods? Is the risk of eating baked, fried, and toasted starches on a daily basis, which contain high levels of acrylamide, a probable carcinogen, far more risky than eating grilled meats. A: In 2005, grains and starchy foods supplied 23% of energy in the U.S. food supply, sweeteners 17%, and plant-sourced oils and fats 23%, whereas meat, fish, and poultry altogether contributed only 15% of daily calories.
This means that Americans probably do get exposed to more acrylamide than HCAs, but it doesn't mean that we should ignore HCAs as a danger. If like a typical American you eat lots of processed grain products containing acrylamide, your risk would only go up by adding grilled meats, since the more carcinogens you consume, the more likely you will reach the limit of tolerance. If you eat a paleo diet and have grilled meats every day, this would present at least as much risk as eating toasted bread every day, if not more.
Q: What actions are within our control and which foods do you think are the most hazardous and pose the greatest risk for cancer and why? A: Most of the time, we control what we eat and how we prepare it or have it prepared. I think that meats grilled well-done present a significant risk for carcinogenesis. Grain products cooked at a high heat also present a risk due to their contents of acrylamide. Also, heated
gluten is "quite mutagenic" so most foods made from wheat, barley, or rye are carcinogenic.
High heat simply is not a good thing to apply to food on a regular basis. Mutagenic activity starts forming at temperatures of 100 degrees C (212 degrees F). The crust of heated food has the most mutagenic activity. Thus avoid forming or eating crusts.
Q: So which cooking techniques do you recommend most and use most at home?
A: Boiling, steaming, poaching, braising, and stewing w/o previous browning produce undetectable levels of mutagenicity. Roasting and baking produce low to intermediate levels of mutagens. Grilling and frying produce high amounts.
I eat a fair amount of my
grass-fattened meats raw, prepared in marinades, like steak tartare. When cooking meats I prepare by stewing, roasting rare, or minimal broiling, which is safer than grilling because the heat source lies above the food, so no juices drip into it. Vegetables I prepare raw or by baking, roasting, boiling, steaming, or brief stir-frying.
Q: Do you think consuming acrylamide from starches cooked at high heats is a bigger risk than grilled meat?A: In equal quantities and frequency I think they present equal risk.
Q: What do you suggest your patients and nutrition students do to reduce the risk of harmful compounds that might be produced during grilling and other forms of cooking?
A: Don't grill often, and when you do grill only briefly (rare) and use a barrier between the flames and the foods to prevent juices falling into flames. The risk is definitely highest for grilling meat to well-done; with regard to colorectal cancer, eating well-done meat leads to a risk 3.5 times greater than the level seen consuming rare meat. If you use a marinade, do not put any oil in it.
Q: I’ve read that some researchers have found evidence eating vegetables with grilled meat changes the way the body metabolizes certain chemicals associated with grilling. I recommend making your vegetable or vegetable and fruit portion at least twice the size of your protein portion. Ideally this will displace grains, which are less nutritious.
A: Yes, when you eat grilled food, I also recommend that you consume it with vegetables and fruits or tea; although inconclusive, evidence suggests the phenols in these foods may help prevent mutations caused by mutagens in grilled meat.
Q: So do the rules about grilling apply to other cooking techniques?
A: Yes. Keep meat away from direct flame and don't let juices fall on the heat source.
Photo right: Rachel Albert,
copyright 2006©.
Q: Is the risk of cancer producing compounds greater for grilled meat than for fish, poultry, or lean meat?A: Not necessarily. The risk mainly comes from the damage done to proteins by high heat. Lower fat content may reduce the risk slightly, but even the leaner meats have enough fats to generate significant amounts of toxic lipid by-products when juices hit the flames. Bottom line, grilling creates serious toxins and I recommend you avoid them as a general rule. Remember, our prehistoric ancestors did not have grills so we had no opportunity to develop a resistance to their toxic effects.
Q: Thanks Don. I really appreciate you taking the time to answer these questions. I know a lot of people wonder what to believe when they read articles about the association between various foods or practices and cancer. Do you have any other suggestions you’d like to add to help people make sense of all the information they’re bombarded with about diet and cancer?A: The only way I have found to make sense of all this information lies in comparing everything we eat and do to food to the only known cancer-free cultures, hunter-gatherers and primitive horticulturalists who don’t eat grains. If they didn’t or couldn’t eat a certain type of food or use a method of cooking, I consider that food or method of preparation a possible suspect in producing or promoting cancer and other degenerative diseases until proven otherwise. Basically, we remain stone age in our physiology, and can’t adapt to new foods or new cooking methods as quickly as we can create them. Learn what our ancestors ate and how they prepared foods, and compare every newfangled item to that baseline.
To read more about Don’s views on food, fitness, pharmacy, freedom, and philosophy using an evolutionary paradigm, visit his blog, Primal Wisdom, which refers to the accumulated wisdom of our pre-agricultural ancestors as well as the innate wisdom built into the modern human organism through millions of years of evolution.
If you're interested in this topic, please subscribe to this blog (you'll see the subscribe button about halfway down this page on the far left side) to receive updates when I post follow ups and other related topics. Im posting part 2 of this interview in a few days.