Marks Daily Apple
Serving up health and fitness insights (daily, of course) with a side of irreverence.
25 Nov

How Bad Is Charred Meat, Really?

Beef steak on grillThere’s nothing like charcoal-grilled meat. It’s not just the food itself, although that’s amazing. It’s the entire experience: being outside in fresh (albeit smokey) air, the sizzle when you slap that meat down on the hot grill, the smell of the smoke. Even the tools we use when grilling are bigger and savager and more rewarding than the dainty implements used inside. We don’t gently flip the steak. We grab it with huge metal tongs and throw it down. There’s less precision and more art. And the flavor can’t be found anywhere else. The smoke, the flame, the char, the grill marks, the color, the dripping fat—they are irreplaceable.

But is it healthy? Is that perfect sear costing you years off your life? Are those BBQ ribs adorning your colonic interior with pre-cancerous polyps?

That’s what we’ve been told happens. That’s what’s supposedly behind the relatively inconsequential increases in colorectal cancer risk seen in red meat eaters. In previous posts, even I’ve recommended gentle cooking techniques and cautioned against excessive intake of grilled, seared, barbecued, and fried meat, especially without using protective marinades and eating protective vegetables. I reiterated this stance a couple weeks ago in my response to the WHO report on red meat and colorectal cancer.

A couple nights back, I found myself hovering over a pair of lamb shoulder chops sizzling on a charcoal grill, watching the marrow render before my eyes, anticipating the blackened lamb fat and caramelized marinated meat. Could it really be so bad? Should I have dropped these chops into a pot of boiling water instead?

As it turns out, I may have overstated the danger of the carcinogenic compounds found in charred meat.

First, let’s look at heterocyclic amines (HCAs), which get the most bad press. HCAs form when sugars, amino acids, and creatine in meat react with heat. They can be carcinogenic in animal studies, and there are weak associations between colon cancer rates and estimated HCA intake in humans. The epidemiology has been covered. The animal studies purporting to show the carcinogenic effects of cooked meat compounds invariably use physiologically-irrelevant conditions; the doses of HCAs that cause colorectal cancer in animals are hundreds of 1000s times higher than the dose of HCAs humans get from cooked meat.

And when researchers try to cause cancer by feeding actual meat, they either come up empty or resort to restricting some nutrients and adding others until they get a hit.

They put the animals on a low-calcium diet. Calcium is known to inhibit the carcinogenicity of cooked meat, and researchers who want to observe colon cancer in lab animals know they have to limit the mineral.

They get things rolling by dosing the animals with powerful carcinogens. Which doesn’t even always work. In one paper, a bacon-based diet actually protected rats against colon cancer after they were injected with a known colon cancer promoter. That must have been an awkward moment in the lab.

They put the animals on a low-fat diet. Feeding well-cooked beef to rats on a high-fat (beef tallow-based) diet did not cause colon cancer in one paper, even after injection with a colon cancer-promoter. Only the rats on low-fat diets got cancer.

In addition to the mechanistic flaws, chicken is a major source of HCAs in the human diet, yet it’s never associated with colon cancer in these epidemiological studies.

A lot of things don’t really add up. While I wouldn’t say HCAs are healthy, I don’t think they’re a huge danger. And even if they’re valid and reflect causality, the associations between red meat and cancer are extremely weak.

Another candidate is heme—the animal-based iron that’s far more bioavailable than plant-based iron. It’s high in red meat and epidemiology links heme iron intake to colon cancer. Animal studies seem to show that heme iron can promote colon carcinogenesis, so what are the proposed mechanisms and do they apply to you and me?

The proposed mechanism with the most support is heme’s oxidative effect on fatty acids. In one study, feeding heme iron to rats promoted colon cancer only when fed alongside high-PUFA safflower oil. Feeding MUFA-rich and far more oxidatively-stable olive oil alongside the heme prevented the colon carcinogenesis. Oh, removing calcium from the diet also promoted colon cancer in the animals, as did the carcinogen they were summarily injected with at the start of the study.

A 2000 study purported to counter the claim that fat has an effect on heme’s toxicity, finding that whether fat was 10%, 25%, or 40% of a rat’s diet had no effect on the carcinogenicity of added heme. There’s no mention of the fatty acid composition of the added fats, but given that most rodent diets (especially 15 years ago) use corn or soy oils, it’s a safe bet that these rats were on 10%, 25%, and 40% vegetable oil diets. 10% of calories from PUFA is quite high and provides plenty of substrate for heme-induced peroxidation. 10% from PUFA may be the “ceiling” after which additional PUFA has no further effect.

A 2004 study had similar results, finding that meats containing medium to high amounts of heme—beef and beef blood sausage—promoted carcinogenic conditions in the colon, while low-heme chicken did not. Sounds bad for red meat, but take a look at the fat source in the animals’ diets: either corn oil or soybean oil, two of the most PUFA-laden, unstable fats available. Would the carcinogenic effects of heme-rich meat persist if the animals were eating MUFA or saturated fat-based diets?

A recent paper offers a potential answer. Mice were split into three groups. One group got heme iron plus omega-6 PUFA (from safflower oil). One group got heme iron plus omega-3 PUFA (from fish oil). The third group got heme iron plus saturated fat (from fully hydrogenated coconut oil, which contains zero PUFA). To determine the carcinogenicity of each feeding regimen, the researchers analyzed the effect the animals’ fecal water (which is exactly what it sounds like) had on colon cells. The fecal water of both PUFA groups was full of carcinogenic indicators and lipid oxidation byproducts, and exposing colonic epithelial cells to fecal water from PUFA-fed mice was toxic. The coconut oil-derived fecal water had no markers of toxicity or lipid oxidation.

If you’re eating lots of polyunsaturated fats with your meat, if you’re cooking your meat in bad oils, or you’re eating meat that’s been cooked in refined high-PUFA seed oils (like most prepared and restaurant food), heme may cause problems. Most people are, which may be why those modest associations between red meat and colon cancer exist. But you’re not doing that, are you?

If you’re still hanging your hat on the heme hypothesis, look again. Given the frequent (if unimpressive) relationship between eating well-done meats and colorectal cancer, you’d think that well-done meat must contain more heme iron than rarer meats. Only they don’t. A paper from 2012 sought to create a heme iron database for various meats according to cooking method. Across the board, the heme content remained unchanged whether the meat was well-done or rare.

In short, the arguments for HCAs and heme iron weaken under scrutiny, especially if we’re talking about people following the Primal eating plan, the paleo diet, or any real-food way of eating that eschews high-PUFA seed oils and emphasizes quality fruits, vegetables, spices, herbs, prebiotic fiber, and antioxidant-rich marinades.

I think I’ll keep enjoying my grilled lamb, and enjoying the grilling of lamb. Not every day, as there’s probably an upper limit and there are so many other good things to eat, but I’m not worried.

What about you, folks? Do you still enjoy grilled/seared-on-the-outside-rare-in-the-middle red meat?

Thanks for reading, everyone. Take care.

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You want comments? We got comments:

Imagine you’re George Clooney. Take a moment to admire your grooming and wit. Okay, now imagine someone walks up to you and asks, “What’s your name?” You say, “I’m George Clooney.” Or maybe you say, “I’m the Clooninator!” You don’t say “I’m George of George Clooney Sells Movies Blog” and you certainly don’t say, “I’m Clooney Weight Loss Plan”. So while spam is technically meat, it ain’t anywhere near Primal. Please nickname yourself something your friends would call you.

  1. Yet another dream come true. This is up there with the green light for bacon, full-fat dairy and KerryGold butter.

    Monikat wrote on November 25th, 2015
    • Exactly!

      Let’s be thankful for this little chestnut:

      “In one paper, a bacon-based diet actually protected rats against colon cancer after they were injected with a known colon cancer promoter. That must have been an awkward moment in the lab.”

      Rusty wrote on November 27th, 2015
  2. I was a vegetarian for over 30 years. I have no problem enjoying a charred steak from time to time, especially a pastured steak from my local market. But nice to know that some of the dangers were overstated. As always, thanks to Mark for presenting a balanced, educated view on the topic!

    Elizabeth wrote on November 25th, 2015
    • Please please tell me how you got past the eating animals part. I actually have a shocking stomach and know it is gluten, lentils and grains have tried going with out one or other and they all affect me. I find it so hard to disconnect from the animal and meat thing. Appreciate any advice.
      Cheers

      fitforlife wrote on November 26th, 2015
      • Not sure if this will help you but my hubby and I don’t want to disconnect our food from being an animal. We acknowledge and give thanks to the animal before we eat and we only purchase our meat and eggs from a local farm where we know the animals were treated as humanely as possible.

        Shauna wrote on November 26th, 2015
        • Thanks for your reply x I am living in Thailand and to be honest I am not sure where the meat comes from as I do not speak enough Thai to ask, Thai people are in general kind to animals so I am only hoping that the animals have been under good care. I have been in the background at Marks Daily for a long time,fighting between conscience and health and just can not keep doing it anymore as it is making me quite sick because I keep eating the lentils and grains. So thank you again for your reply I will think along those lines xx

          fitforlife wrote on November 26th, 2015
        • Conscious never was a part of our diet until we always had plenty of food to be selective. And then the Seventh Day Adventists came along with their vegetarian diets.

          Humans evolved as omnivores. Eat animals and animal products. Yes, it’s good to find humanely farmed sources. But the bottom line is that those animals are not giving you a pat on the back for not eating them.

          Mankind is the only animal that will eat poorly our of conscience. What’s with that?

          OnTheBayou wrote on November 27th, 2015
  3. the arguments for HCAs and heme iron weaken under scrutiny

    That would depend on who’s doing the scrutinizing. If the scrutinizer has a monetary or political agenda to uphold, then he/she will take full advantage of the public’s naiveté. Good thing we have people like you, Mark, to help unravel the mysteries of medical research comprehension.

    Wenchypoo wrote on November 25th, 2015
  4. “Do you still enjoy grilled/seared-on-the-outside-rare-in-the-middle red meat?”

    Absolutely, almost every day for the past several years.

    I use charcoal when I can (even tho it’s not exactly legal in the high rise condo where I live), and when I can’t, I cook on an electric grill and then hit the meat with a blow torch (I’m not joking!) to give it that little something something.

    mrfreddu wrote on November 25th, 2015
  5. If HCAs are formed by reaction of sugars with protein and creatine, perhaps leaving sugars out of the marinade might be good?

    I loathe sugar/honey on my meat, so I brush the raw steak or chops with melted fat and rub in the spices I want to use. The meat sits at room temperature for a couple of hours before I grill it, and it’s always tender and tasty.

    SuzU wrote on November 25th, 2015
    • I agree! Most BBQ sauces contain sugar, as do some marinades. I don’t like burnt-on sauces or sweet-tasting meat so we leave all that stuff off. We seldom even bother to marinate the meat, choosing instead to just season and grill it after it has come to room temp. Prior to serving, I like to top the cooked steaks with a big pat of Kerrygold butter to which I sometimes add chopped herbs. Simple and delicious.

      Shary wrote on November 25th, 2015
      • Boy that sounds good.
        I like my steak crawling off the plate and often eat Carpaccio. Rare to raw and I’m in heaven.

        Noconago wrote on November 25th, 2015
  6. Nothing like stacking the deck to get the propaganda down right!

    Groktimus Primal wrote on November 25th, 2015
  7. When Grok discovered fire, wasn’t he grilling and charring his meat as the only cooking method known to him? He would’ve gotten cancer long ago and might’ve been wiped off from the face of the earth if its so dangerous.

    Sana wrote on November 25th, 2015
    • Hunting is hard, often unsuccessful, even today. Without a doubt Grok didn’t get nearly as much meat as we do. Big piles of bones and tools indicate no more than that Grok lived in that place a long time.

      Rick wrote on November 25th, 2015
      • Hunting isn’t hard when you have the proper loc and tools.
        The central European woodsmen used “High-Seats” in the trees and waited there in the early morning or early evening hours for mass numbers of deer to comes out of the woods into the meadows to graze.
        They threw their spears down into the deer. A group of 6-10 men would get about 3 deer on average PER DAY for their tribe.

        The Laplanders gang’ed-up on sea mammals resting on the beaches, or making nets to catch large amounts of Lachs traveling up and down rivers.

        You have to remember that the balance between man and animal was way different than it is now in 2015.
        Back then, Europe had LARGE amount of wild animals available year round, there was an abundance of Aurox (the european version of a buffalo).
        Most died off with population growth.

        Arty wrote on November 25th, 2015
        • That’s almost the same method used today by a lot of hunters, though we aren’t allowed to use a spear in most paces in the US. Affix a tree stand to a nice, tall tree in the wee hours of the morning or evening, and hit your deer with an arrow through the vitals.
          There was a recent story I read about a guy in Missouri taking down a nice buck using an atlatl, which is pretty hardcore.
          I prefer a rifle, myself, because if you hit a deer with it, it’s likely to drop in its tracks almost instantly.

          His Dudeness wrote on November 25th, 2015
      • Hunting is fun , there are far fewer animals now , you need a license and a tag.

        Less Humans , more animals , more time spent hunting, hunting would have been easier even with less advanced weapons.

        I have no idea how much meat Grok ate, but it wasn’t from unsuccessful hunting.

        Zen MC wrote on November 26th, 2015
        • I use an Atlatl but haven’t been able to use in Wisconsin yet for hunting soon tho I hope

          paul wrote on November 27th, 2015
  8. I revisited the recipe for grill-roasted prime rib (under related posts above). It sounds like a good no-nonsense recipe that I plan to try this Christmas. I have to say, however, that partially cooking it two days ahead of time (if I understood that correctly) is going to result in prime rib that tastes like leftovers.

    Shary wrote on November 25th, 2015
  9. I’ve always had a hard time believing charred meats are any more harmful than non-charred meat of the like.

    I try to imagine our ancestors when they first had access to fire and hoards of meat… did they roast it indefinitely over the fire? Did they cook it until it was semi black so they knew the meat was cooked?

    Or did they gently cook it? I have a hard time believing they gently cooked it over a fire. I think it’s more plausible they slapped a good chunk of the animal over the fire and left it there and pulled pieces off as they needed it.

    When i think of things like colorectal cancer, I think it’s more plausible than things like sugar and excessive insulin are more behind it.

    Brian wrote on November 25th, 2015
    • When our meat-eating ancestors had too much meat they would dry it and smoke it till it became jerky. Maybe we need another set of tests to determine what the effects are of meat-jerky.

      Jed wrote on November 25th, 2015
    • About excessive insulin – protein in meat causes insulin to jump, even more than carbs. Besides the insuling growth factor meat also has a methionine – a growth factor utilizing mTOR pathway. So it is a growth signal even stronger than carbs.

      Outside of this – some cancers are crucially dependant on glutamine (so called “glutamine addiction), which meat is a rich source of.

      GTR wrote on November 29th, 2015
  10. Thank you for this post. I have questioned the validity of the charred meat scare because #1 – I love charred meat!, & #2 – People have been eating charred meat for thousands of years. I just didn’t see how it could be that toxic.

    Valerie North wrote on November 25th, 2015
  11. “In one paper, a bacon-based diet actually protected rats against colon cancer after they were injected with a known colon cancer promoter”

    Another benefit of my bacon consumption! Too bad we are told just the opposite, that bacon is correlated to degenerative disease.

    I have had bacon and eggs for breakfast so many times in my life I couldn’t count, and it is by far my favorite breakfast. I never tire of it – just the opposite. If I cannot have bacon and eggs for breakfast I am disappointed.

    grisly atoms wrote on November 25th, 2015
    • Also interesting that the low fat, no meat eating mice were actually MORE prone to the cancer – that’s going to upset a lot of vegans I guess…

      Like mark said, maybe the big factor here is the OILS being eaten by the Rats, the ironry being that eating these oils with saturated fat, they get displaced by the saturated fats being eaten, helping to reduce the damage.

      Tribal Barbarian wrote on November 25th, 2015
  12. Makes sense to me! The old films I’ve seen at museums of hunter-gatherers left around the world (1950’s or thereabouts) show them cooking monkeys and other meat in a coal fire.

    OctoberAmy wrote on November 25th, 2015
  13. I like charred meat so I just formed a belief that fiber from vegetables, fruit, and psylium simply carry out any nasty carcinogens. It’s not very scientific, but I sleep well. This has saved me a few times from long articles that prove my premise. :)

    Jay wrote on November 25th, 2015
  14. Well … I’d prefer that my wife slow roast our turkey tomorrow and not char it. :)

    HealthyGuy wrote on November 25th, 2015
  15. I reckon this is a good post and I hope you’re correct as I don’t expect to stop using the outdoor grill soon. Too much home kill to get through. Nothing like your own beef or lamb on the grill. I certainly know what it ate and how it died.

    Yum.

    kem johnson wrote on November 25th, 2015
  16. What about the issue of “oxidized” cholesterol? I understand the deal with hydrogenated oils and frying…but I’m not clear on high heat on natural fats.

    TimmyVega wrote on November 25th, 2015
  17. Great article, thank you! I am going to marinade my guilt-free grass-fed steak now :).

    Mary Thomas wrote on November 25th, 2015
  18. So many studies. So much money spent on so many studies. Experiments. Space travel. When really it’s simple, isn’t it? Look after the planet on which we live. Eat Real, Unprocessed Food. Take it easy. And accept the fact that death is going to come, in one way or another, and will probably involve a little suffering.

    Angie wrote on November 25th, 2015
  19. Hey, very good post, great to know these data! Were you able to find anything about the PAHs?

    R wrote on November 25th, 2015
  20. Mark, I hope you can hear the sigh of relief coming all the way from the mountains of Patagonia Argentina. Asado (outdoor bbq) using mostly hardwoods for fire is a way of life down here, and I’ve been concerned for a while about my habit of searing beautiful range-fed beef.

    The detailed insights you provide are precisely why I enjoy reading your site. Thanks again.

    If you ever venture to the End of the World, I’ll treat you to a traditional gaucho feast.

    Memo Stephens

    Memo Stephens wrote on November 26th, 2015
  21. Sous-vide cooking can ensure a “done” steak while reducing grill time. Cook to just short of desired done-ness by temperature (about 125F for medium rare) and then about 30 seconds per side on the grill. You can run the grill very hot as the meat is already cooked, no worries about the center being raw when the surface is done nor center cooked through but surface charred black and over-cooked. To cook for a mass of people you can get a lot of meat ready, then only have to brown the surface when the mass is ready to eat.

    (You can cook rare via sous-vide, but holding at temperature before searing and eating is not a good idea. As long as you trust your supply you can eat rare meats, but the temperature is within the “danger zone” for being held at that temperature for an extended time. What might be good for the family dinner would not hold true for large scale as the mass never gets to the table at the optimum time, some holding at temperature can’t be avoided.)

    James wrote on November 26th, 2015
    • Good pointers for those who like cooking their steak in a plastic bag. Personally, I’d rather pan fry it in a combo of butter and bacon fat or just throw it on the grill right from the get-go. Why the extra step of sous vide?

      Shary wrote on November 26th, 2015
      • For someone who wants to ensure their meat is sufficiently done and can sear it a bit afterwards rather than doing the entire cooking on the grill, in the pan, or under the broiler. There are other things that can be done sous-vide, not just meats.

        And it’s not like you *require* a fancy circulator, you can do it with a beer cooler and a probe thermometer.

        James wrote on November 29th, 2015
  22. How bad or good is the consumption of meat on a daily basis?

    Rebecca Brooke wrote on November 26th, 2015
  23. Once again, common sense prevails. Honestly, it’s not rocket science- it’s food aka fuel. Mimic the way your own personal ancient ancestors ate and you will be healthy. Obviously one size does not fit all. Northern Europeans had different dietary needs than peoples from tropical climates.
    I am of Irish decent. My research tells me that my early ancestors ate a ton of hazelnuts, wild boar, leafy greens like cress, berries, and honey. Later they became a cattle society. Lots of beef and dairy. Celts also have always been fond of alcohol; this is documented in the earliest written accounts.

    Allison wrote on November 26th, 2015
  24. This hypothesis seems mostly correct, pufa in general is a bad thing, especially when coupled with iron. I can’t help but wonder though, in the mouse study you quote on SFA protecting against HCA, you left out the part where ALL rats, including the SFA rats had a higher incidence of stomach cancer.

    Palva wrote on November 26th, 2015
  25. What about charred starch? And acrylamide?

    Coco wrote on November 26th, 2015
  26. I always suspected as much! We eat grilled lamb at least three times a week. Along with grilled eggplant, grilled peppers, grilled tomatoes & grilled garlic. And good, old Red Wine — all organic, of course! And lots of EVOO.

    judith griffin wrote on November 26th, 2015
  27. We’ve been eating cooked – meaning charred on the coals – meat for almost one million years. No PUFA’s in that mastodon tenderloin. Mother Naure usually “knows” what’s best for you.

    OnTheBayou wrote on November 27th, 2015
  28. We couldn’t have made it through 100,000 years of evolution if charred meat was gonna do us in.

    shannon wrote on November 27th, 2015
  29. GTR wrote on November 29th, 2015
  30. I purchased the DNAFit test you recommended and my results came back with a warning about potential DNA damage from chargrilled/smoked meats. This sucks because I love grilling and smoking meats.

    However, I now have more information and can mitigate long-term risk by moderating intake.

    The more you know…

    Jason wrote on November 30th, 2015
  31. This raises an interesting question. The research indicates, as Mark wrote: “If you’re eating lots of polyunsaturated fats with your meat, if you’re cooking your meat in bad oils, or you’re eating meat that’s been cooked in refined high-PUFA seed oils…heme may cause problems.”

    So, what about foods like wild salmon? Clearly it has its share of PUFA’s. Wouldn’t this suggest that grilling salmon (which is a decent source of iron, similar to chicken) might also be bad for you?

    JKinNY wrote on December 2nd, 2015
  32. Things being what they are, shouldn’t something be said about sustenances such as wild salmon? Unmistakably it has its offer of PUFA’s. Wouldn’t this recommend barbecuing salmon (which is a respectable wellspring of iron, like chicken) may likewise be terrible for you

    shonali wrote on March 24th, 2016

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