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Let me introduce myself. My name is Mark Sisson. I’m 63 years young. I live and work in Malibu, California. In a past life I was a professional marathoner and triathlete. Now my life goal is to help 100 million people get healthy. I started this blog in 2006 to empower people to take full responsibility for their own health and enjoyment of life by investigating, discussing, and critically rethinking everything we’ve assumed to be true about health and wellness...

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April 30 2019

Does Red Meat Give You Colon Cancer?

By Mark Sisson
14 Comments

Have you heard? There’s a new “red meat will kill you” study. This time, it’s colorectal cancer.

Here’s the press release.

Here’s the full study.

I covered this a couple Sundays ago in “Sunday with Sisson.” If you haven’t signed up for that, I’d recommend it. SWS is where I delve into my habits, practices, and observations, health-related and health-unrelated—stuff you won’t find on the blog. Anyway, I thought I’d expand on my response to that study here today.

How the Study Was Conducted

It’s the basic story you see with most of these observational studies. Around 175,000 or so people were asked to recall what they ate on a regular basis—a food frequency questionnaire. This is the exact questionnaire, in fact. The research team took the answers, measured some baseline characteristics of all the subjects—socioeconomic status, exercise levels, whether they smoked, education level, occupation, family history of colorectal cancer, and a few others—and then followed up with participants an average of 5.7 years later to see how many had developed colorectal cancer.

What the Study “Showed”

Those who had moderate amounts of red meat had a 20% higher chance of getting cancer.

And in the end, the increased risk was a relative risk. It wasn’t a 20% absolute increase in risk. It was a relative increase in risk. The subjects started with a 0.5% risk of getting bowel cancer. In those who ate the most processed meat and red meat, that risk increased 20%—to 0.6%!

From 0.5 to 0.6%. Sure, that’s an increase, but is it something to overhaul your entire diet for? To give up the best sources of zinc, iron, B vitamins, protein, carnosine, creatine? All that for a measly 0.1% that hasn’t even been established as causal?

Study Findings Most News Outlets Won’t Include

One head scratcher that leaps out: the link between unprocessed red meat and colon cancer was not actually statistically significant. Only processed meat was significantly linked to colon cancer.

Another head scratcher: red meat, whether processed or unprocessed, had no significant association with colorectal cancer in women. Why didn’t they highlight the fact that in women, eating red meat was completely unrelated? That’s half the world’s population. That’s you or your mom, your daughter, your grandmother, your girlfriend. And unless they were to look at the full study and read the fine print, they’d never know that red meat actually had the opposite relationship. You’d think the authors would want to mention that in the abstract or see that the press releases and media treatments highlighted that fact.

It’s probably because mentioning that red meat was neutral in women and had no statistically significant link to colon cancer in men and women would have destroyed their case for red meat as an independent carcinogen. See, carcinogens are supposed to be carcinogens. There are many meaningful differences between men and women, but a poison is a poison.

What’s the proposed mechanism for red meat triggering colon cancer in men but not in women? If they didn’t have one (and I imagine they wouldn’t have mentioned it if they did), then there’s probably something else going on.

Besides, the literature is far from unequivocal.

What Other Research Says About Red Meat and Bowel Cancer

In analyses that include consideration of cooking methods and other mitigating factors, red meat has no relationship with colon cancer.

Or what about this study, where colon cancer patients were more likely to eat red meat, but less likely to have type 2 diabetes? Should people avoid red meat and work toward getting diagnosed with type 2 diabetes?

Or how about this study, which found no difference in colorectal cancer rates between people who ate red meat-free diets and people who ate diets containing red meat? Shouldn’t the diet without any red meat at all have some effect?

Or this classic study, where rats on a bacon-based diet had the lowest rates of colon cancer. In fact, bacon protected them from colon cancer after they were dosed with a colon cancer promoter, while rats on normal “healthy” chow were not.

The Blind Spot In Red Meat Research

I don’t need to go into all the confounding factors that might predispose conventional red meat lovers to bowel cancer. Nor will I mention that it’s impossible to fully control for variables like the buns and bread and fries you eat the red meat with and the industrial seed oils it’s cooked in.

That last bit is crucial: the seed oils. It’s what nearly every cancer researcher misses. It’s not just a minor variable; it’s quite possibly the most important determinant of whether meat is carcinogenic in the colon or not. Heme iron—the compound unique to red meat that usually gets the blame for any increase in cancer—is most carcinogenic in the presence of the omega-6 fatty acid linoleic acid.

In one studyfeeding heme iron to rats promoted colon cancer only when fed alongside high-linoleic acid safflower oil. Feeding MUFA-rich and far more oxidatively-stable olive oil alongside the heme prevented the colon carcinogenesis.

Another 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 when the fat sources were linoleic acid-rich corn and soybean oil.

And most recently is this paper. 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.

I never see these (animal) studies cited in observational studies of meat and colon cancer. I think that’s a huge blindspot, and it’s one of the reasons I rarely put any stock in these scary-sounding studies.

That’s it for today, folks. Thanks for reading. Now go enjoy a steak.

I just might do that myself—my favorite grass-fed steak actually. Check out Butcher Box if you’re looking for cooking inspiration—and an excellent source for healthier, grass-fed, pastured and heritage breed meats. Full disclosure: I’m an affiliate—but also a long-time happy customer. Thanks again, everybody.

References:

Bylsma LC, Alexander DD. A review and meta-analysis of prospective studies of red and processed meat, meat cooking methods, heme iron, heterocyclic amines and prostate cancer. Nutr J. 2015;14:125.

Alsheridah N, Akhtar S. Diet, obesity and colorectal carcinoma risk: results from a national cancer registry-based middle-eastern study. BMC Cancer. 2018;18(1):1227.

Rada-fernandez de jauregui D, Evans CEL, Jones P, Greenwood DC, Hancock N, Cade JE. Common dietary patterns and risk of cancers of the colon and rectum: Analysis from the United Kingdom Women’s Cohort Study (UKWCS). Int J Cancer. 2018;143(4):773-781.

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14 thoughts on “Does Red Meat Give You Colon Cancer?”

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  1. Thanks Mark, when I saw the headlines I just knew you’d come along a week later and put all of our minds at ease.
    I hope you make millions selling your Primal Pantry products because the information you give out for free is priceless.

  2. Good lord … from .05 to .06 % … give me a break.

    I don’t eat much red meat, but I do some and have no qualms about it. My primary focus is on clean sources of meat and not to burn if grilling, that’s what you DO need to be concerned about IMHO.

    If you’re eating berries, green and multi-colored veggies, collegen, drinking green tea, olive oil, bone broth etc. you should realize protective benefits. I do recommend getting a colonoscopy at age 40 and thereafter as resluts dictate.

  3. I just read that if you want to reduce your intake of nasty red meat you should switch to lean, healthy bison. (Bison: the other white meat. Who knew?) Just finishing off quarter of grass fed beef and replaced it with a freezer load of bison. The bison is so red it looks purple next to the much paler grass-fed beef. I’m seeing iron (which I never seem to get enough of), protein, omega 3 fats, B vitamins, and minerals. I can’t imagine how avoiding a good source of so many nutrients that aren’t readily available in a grain based diet would be healthy.

    1. Are you for real? Red meat is nasty and Bison meat that is also red is the other “white meat”? That reminds me of the marketing of pork meat as white. If it’s white meat you are after stick to chicken breast no thanks. The problem is with the grass fed meat you were buying not all grass fed meat. Simply put, it was sourced from growers that butcher the animals far too early and that means that it will also be lean. Get grass fed meat of a cow that grazed for 3 years and you see what you’ve been missing.

  4. I’d like to go enjoy a steak… Alas, the only red meat I can afford regularly is frozen burgers…
    Also, is it a bad sign if whenever I do eat a steak, my digestion feels insanely sluggish? Could some people just have a harder time breaking down red meat, and could a lifetime of very infrequent red meat consumption be the cause of that? I grew up eating mostly chicken and processed pork products with some ground beef once or twice a week and the very, very occasional steak.

    1. I had that problem when I was having carbs with the meat. If it’s meat+sauteed greens, I have no issues digesting it. My body just dan’t do bread + meat.

    2. There’s a perfect explanation to your inability to digest meat and the answer is in the question; Low stomach acid. Get yourself good quality HCL capsules (hydrochloride) and digestive enzymes

      1. This. I know through experience my body doesn’t make enough HCl, so I add a minimum of 6 or more betatine HCL caps, plus 3-4 digestive enzyme caps, per meal. The more HCl, the better my body digests what I do eat.

  5. Relative risk is bunk. However, if a person is a “meat and potatoes” type and avoids greens as “rabbit food” they’re going to have problems, especially with rampant sedentary living today. From a socioeconomic perspective, it’s the same diff if you’re just too poor to be able to risk buying food that may spoil before you can eat it. And therefore, if you avoid fresh foods, but spend a bit on meat, then it’s likely to have a less than ideal effect. Since the gut is mainly made of collagen, the most important factor is the total amount of Vitamin C in the diet. Probably. I’m pretty sure they haven’t studied it, maybe out of fear that it might lead to a fact? Or am I just feeling cynical today?

  6. I wish more emphasis was put on eating more veggies rather than trying to vilify meat. Oh, well. I guess “eat your broccoli” doesn’t make for a good click bait article title.

  7. Is it just me who heard the line in the song that goes…. “ya can’t have any pudding if ya don’t eat yer meat”?
    I tried years ago to stop eating red meat (AKA beef), after a couple of months I thought I was going to die…. I was so tired all the time….. one day I thought I just need a steak! …. bought one, cooked it up and VIOLA, felt better and that was the end of my getting rid of red meat.

    1. I saw Pink Floyd live three times … so no … it’s not just you. 😉

    2. I haven’t had any red meat in nearly a year and I have no such trouble with fatigue.

  8. I think cancer is more of an environmental cause than red meat. I my self had colorectal cancer and have never been a heavy red meat eater. My background is construction and military. So I tend to think that was more of the cause of my cancer. My brother died of cancer but not colon. He was in the automotive industry. He also had a lot of diet soda intake. I am pretty sure that had a lot to do with his cancer also.