According to the World Health Organization, consumption of red meat may cause cancer in humans, and processed meat does cause cancer in humans. Here’s what they had to say about eating “red” meat:
After thoroughly reviewing the accumulated scientific literature, a Working Group of 22 experts from 10 countries convened by the IARC Monographs Programme classified the consumption of red meat as probably carcinogenic to humans (Group 2A), based on limited evidence that the consumption of red meat causes cancer in humans and strong mechanistic evidence supporting a carcinogenic effect.
And here’s what they had to say about “processed meat”:
Processed meat was classified as carcinogenic to humans (Group 1), based on sufficient evidence in humans that the consumption of processed meat causes colorectal cancer.
And:
The experts concluded that each 50 gram portion of processed meat eaten daily increases the risk of colorectal cancer by 18%.
50 grams of processed meat (where “processed” is not really defined very clearly, but includes salted, cured and smoked products) is around 2-3 slices of bacon. “Red” meat includes beef, pork, veal, lamb, goat and horse.
I am not in the pay of the meat industry, and in fact meat makes up a fairly small component of my diet most days. We eat a lot of beans and grains chez Peyton, and when we do eat animal products, it’s usually chicken. But I do love meat and sausage and hot dogs and bacon and all manner of processed meats. My guess is that I eat less red meat than the average for the U.S., (which is apparently about 71 pounds per person annually) but above the amount recommended by the WHO, which is apparently “little to none.”
I am also not a conspiracy theorist, and I am not the kind of man to deny scientific evidence of something based on my personal inclination or political beliefs. I’ve read studies over the last decade that suggested a link between meat (particularly grilled meat) and cancer, I accept that we can, in fact, infer causation from correlation, even if we do not fully understand the mechanism behind the causation.
The correlation between smoking cigarettes and many forms of cancer, for example, is well-documented, and if we can’t precisely pinpoint the link between the exposure and the disease, that’s not to say there’s no relationship. Further, the WHO is not saying that all carcinogens carry the same risk of causing cancer.
As I’ve said, I’m not a conspiracy theorist, but I do wonder whether the overall cost of producing meat, particularly beef, was a factor in the WHO’s decision to release the report. The logic, I suppose, would be that the environmental cost of producing meat far outweighs its nutritional value. That’s a debate for another day.
My concern is that the WHO report will affect how people generally view these sorts of warnings – I can assure you that the meat industry will be pointing out all of the other things that the WHO has classified as carcinogenic (of which, more below) in an attempt to blunt the impact of the report. Then, too, we’ve been inundated with claims by scientists of varying respectability for decades about what we should or shouldn’t eat, including whether some particular food or another either causes cancer or acts as a preventative. I think a lot of people are going to look at this study as just more of the same. The danger is that the WHO may lose some of the public’s respect, and that’s a bad thing, I think.
I want to stress that my opinion about the WHO report is my own and not that of the fine folks at Renaissance Publishing, my family, friends, acquaintances or people who have walked past me in a crowd. Moreover I have not read all of the (800+) studies on which the report is based. Here are some things I have read:
Here is an article that purports to explain the findings at the Lancet, a prestigious medical journal based in the UK. You’ll have to register to read it, but registration is free, and there’s a lot of good stuff in that article.
Here is what amounts to an FAQ on how the IARC (the International Association for Research on Cancer – a division of the WHO) works, including a discussion of the difference between “risk” and “hazard.”
Exposure is usually defined in terms of volume and time; in other words, how much were you exposed to, and for how long? There’s another consideration, which is what else were you exposed to that might be relevant to the subject of the study? Here’s what the Lancet article, linked above, said about that on a very basic level:
The Working Group assessed more than 800 epidemiological studies that investigated the association of cancer with consumption of red meat or processed meat in many countries, from several continents, with diverse ethnicities and diets. For the evaluation, the greatest weight was given to prospective cohort studies done in the general population. High quality population-based case-control studies provided additional evidence. For both designs, the studies judged to be most informative were those that considered red meat and processed meat separately, had quantitative dietary data obtained from validated questionnaires, a large sample size, and controlled for the major potential confounders for the cancer sites concerned.
(emphasis added)
That last part I’ve put in italics is the kicker – the studies deemed most informative were those that, among other things, controlled for the major potential confounders for the cancer sites concerned. Meaning the studies deemed less informative did not, I guess? So does that mean that the less informative studies didn’t take into account whether the participants smoked, worked with friable asbestos, spent six hours a day in tanning beds or engaged in other activities that have been correlated with an increased risk of developing cancer?
Does it suggest that other studies that were considered “less informative” did not consider red meat and processed meat separately, did not have quantitative dietary data obtained from “validated” questionnaires and relied on a small sample size? How much weight did the “less informative” studies carry?
Here’s another excerpt from the Lancet:
The largest body of epidemiological data concerned colorectal cancer. Data on the association of red meat consumption with colorectal cancer were available from 14 cohort studies. Positive associations were seen with high versus low consumption of red meat in half of those studies, including a cohort from ten European countries spanning a wide range of meat consumption and other large cohorts in Sweden and Australia. Of the 15 informative case-control studies considered, seven reported positive associations of colorectal cancer with high versus low consumption of red meat. Positive associations of colorectal cancer with consumption of processed meat were reported in 12 of the 18 cohort studies that provided relevant data, including studies in Europe, Japan, and the USA.
Again, I’m probably not smart enough to fully understand the above, but it looks to me like of the 800 studies, “half” of 14 showed an association between eating red meat and colorectal cancer, and 2/3 of the studies on processed meat showed an association with cancer.
The report does not conclude that eating meat = cancer by any means. Here’s yet another quote:
On the basis of the large amount of data and the consistent associations of colorectal cancer with consumption of processed meat across studies in different populations, which make chance, bias, and confounding unlikely as explanations, a majority of the Working Group concluded that there is sufficient evidence in human beings for the carcinogenicity of the consumption of processed meat. Chance, bias, and confounding could not be ruled out with the same degree of confidence for the data on red meat consumption, since no clear association was seen in several of the high quality studies and residual confounding from other diet and lifestyle risk is difficult to exclude. The Working Group concluded that there is limited evidence in human beings for the carcinogenicity of the consumption of red meat.
(emphasis added)
Gist: Eating “processed” meat causes cancer, and maybe eating “red” meat does too, at least according to “a majority” of the working group.
Just to put this in context, other things classified as carcinogenic on the same level (group 1) as “processed meat” include acetaminophen, aflatoxins, alcoholic beverages, arsenic, asbestos, benzene, betel quid (with or without tobacco), diesel exhaust, estrogen-progestogen in oral contraceptives and menopausal therapy, fission products (including strontium-90), formaldehyde, HIV type 1, multiple-types of HPV (herpes), leather dust, a shit-ton* of things starting with “methyl,” neutron radiation, outdoor air pollution and the particulate matter therein, being a painter, PCBs, plutonium, a few radium isotopes and their decay products, Chinese-style salted fish, solar radiation (sunlight), tobacco, UV radiation and X- and gamma radiation.” (My proposed new WHO slogan: “AVOID CANCER: EAT KALE IN THE DARK”)
(*my term, not a scientific measure)
I have no reason to believe that the WHO is in the grips of some sort of vegan-inspired frenzy. My guess is that they mean well, and honestly we could probably all stand to eat less meat generally and processed meat specifically.
But I have a very difficult time conceiving of a study performed in the United States that could adequately control for “confounding” factors as regards any cancer, and specifically colorectal cancer. And I’ll bet you that’s the case for Europe, Japan and Australia, where most of the studies appear to have been conducted took place.
I am probably wrong. And please note again that the WHO is not saying that if you eat bacon you will get colorectal cancer. What the WHO is saying is that if you eat 2-3 slices of cancer a day, you are, generally, 18% more likely to get colorectal cancer than if you abstained from eating 2-3 slices of bacon a day.
How they reached that percentage is beyond me, but ultimately the question is whether you are willing to bear the increased risk of consuming red and/or processed meats, taking into consideration what else you do that affects your risk of contracting cancer, your inherent risk factors (including your genetics and family history) and how all of that affects your quality of life.
Me? I cooked spicy pork meatballs with tofu in black bean sauce for dinner after reading the report. I’ll probably eat meat, maybe even processed meat, three or four more times this week. I don’t doubt that cutting down on the consumption of red and processed meats has a health benefit, and that as a society we should do it, but I’ll wait to be convinced that there’s a significant, direct link between eating meat and cancer that can’t be explained by other factors. I’ll apologize if I’m wrong; it won’t be the first time, but in the interim I’m going to continue to enjoy my semi-carnivorous diet.
