Debunked: What the Health: Meat and Cancer

Dan Wilson

Senior Member.

"What the Health" is a documentary that is gaining popularity and has already caused a frenzy of debunking, rebuttal, and re-rebuttal articles and videos from various media sources. It documents filmmaker Kip Anderson's investigation of the animal product industry. In order to avoid this forum becoming a mess, I want to stick with one claim here: red and processed meats cause colorectal cancer.
This claim comes up in the first 5 minutes of the film and refers to a report from the World Health Organization (WHO) that led to the classification of processed meats as a group 1 carcinogen and red meats as a group 2A. This means that there is sufficient evidence to say that processed meats increase risk of colorectal cancers but the case with red meats is not as certain. This claim itself is absolutely correct. Like so many things in this film, however, the interpretations and conclusions made from such information are dishonest.
Because of this classification, Kip compares the idea of eating meat to smoking and questions why children are allowed to eat processed meats. He also emphasizes that processed meats are in the same category as asbestos and plutonium. The misunderstanding here comes with the way the International Association for Cancer Research (IARC) classifies carcinogens. The classification system works by probability, not how dangerous the substance is. In other words, the classification system answer the question, how strong is the evidence that this substance can increase my risk of getting cancer? It does not assess how carcinogenic something is. For perspective, alcohol is also listed as a group 1 carcinogen and the profession of being a barber is classified as a group 2A carcinogen. This does not mean any of them are comparable.
A better way to think about this is to look at the estimated deaths attributed to each carcinogen. From the IARC Q&A page: http://www.who.int/features/qa/cancer-red-meat/en/

12. How many cancer cases every year can be attributed to consumption of processed meat and red meat?
According to the most recent estimates by the Global Burden of Disease Project, an independent academic research organization, about 34,000 cancer deaths per year worldwide are attributable to diets high in processed meat.

Eating red meat has not yet been established as a cause of cancer. However, if the reported associations were proven to be causal, the Global Burden of Disease Project has estimated that diets high in red meat could be responsible for 50,000 cancer deaths per year worldwide.

These numbers contrast with about 1 million cancer deaths per year globally due to tobacco smoking, 600,000 per year due to alcohol consumption, and more than 200,000 per year due to air pollution.
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From this information, Kip concludes that meat is a dangerous carcinogen that should never be eaten and that everyone who eats it is in grave danger of getting cancer. This conclusion is harsh and dishonest for two reasons. 1) According to the report, the increase in colorectal cancer risk that comes with consuming 50 grams (0.11 lb) of processed meat a day comes out to about an 18% increase. That 18% is not a net increase, it is relative to the baseline risk, which is about 5%. This means that by eating 50 grams of processed meats a day, you increase your risk of colorectal cancer from 5% to 5.8%. 2) Eating a reduced amount of meat will make this risk negligible.
This scientific information does not warrant mass warnings and drastic lifestyle changes. What it does warrant is a strong reminder that diet is important for health and cancer prevention and we should be mindful of how balanced our meals are. Going vegan can be a great decision for many reasons. The decision does not have to employ pseudoscience and scare tactics.
 
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Going vegan can be a great decision for many reasons. The decision does not have to employ pseudoscience and scare tactics.

Totally agree. Thank you for this post. As an advocate of animal welfare, I hate the pseudoscience a lot of vegans and vegetarians believe in. And this is only the tip of the iceberg lettuce.
 
Thanks for this. Sadly these dishonest scare tactics can do more harm than good.
Actually, this may be one of the rare occasions where dishonest scare tactics could (were they actually heeded) do a lot more good than harm - and I'm not talking just in terms of human lives.

But that's another topic. ;)
According to the report, [...] by eating 50 grams of processed meats a day, you increase your risk of colorectal cancer from 5% to 5.8%.

Why quote the figure of 50 grams per day? Average consumption of red meat in the US is well in excess of 100 grams per day, and the recommended maximum amount seems to be around 70 grams per day. 50 grams, therefore, is well within the 'safe' region.

What are the risk figures for 100 grams per day? Or for amounts in excess of that?
 
One place I looked was here: www.npr.org/sections/thesalt/2012/06/27/155527365/visualizing-a-nation-of-meat-eaters
At 270.7 pounds per person a year, [the US] eats more meat per person than in almost any other country on the planet. Only the Luxumbourgers eat more meat than we do.
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That's 336 grams per person per day - though that figure is for all meat. They also have a graph which shows consumption of the four most popular animals: beef + pork looks to be about 100 pounds pppa, which equals about 125 grams per person per day.

Those stats in turn come from the Food and Agriculture Organization of the United Nations (FAO), and the (now defunct) Earth Policy Institute respectively.
 
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beef + pork looks to be about 100 pounds pppa, which equals about 125 grams per person per day.
hmm, while I don't disbelieve those numbers ( I think I ate half a pound in my spaghetti sauce last night!), not sure about the source "Earth Policy Institute". :)

a 2004 breakdown is probably a bit more reliable.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3045642/
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@Dan Wilson 's 50g was for processed meats though. Not all meats are created equal re: cancer.
 
Not all meats are created equal re: cancer.
Agree with that.

So it looks like some discrepancy with the figures. The table you posted shows, for total meat, just over 103lbs per person per annum, while the figure from the FAO was 2.6 times that (271lbs).

The FAO figure is also the one used on wikipedia (265lbs pppa for 2009). There, I read:
[This figure does] not represent per capita amounts of meat eaten by humans, [but] figures for carcass mass availability, divided by population. Carcass mass availability does not account for losses, which include bones, losses in retail and food service or home preparation (including trim and cooking), spoilage and “downstream” waste, and amounts consumed by pets. As an example of the difference, when the 2002 FAO figure for US per capita meat consumption was 274.4lbs, the USDA estimate of US per capita loss-adjusted meat consumption was 138lbs.
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So it seems like the NPR article was somewhat misleading, and that actual consumption may be around half that of the wonderfully-named 'carcass availability'.

Split the difference? (138+103)/2/365*454 = 150 grams of meat per person per day (of which, going by the table you posted, maybe half is red (~75g) and 20% (~30g) is processed).

Good news! Pigs in blankets are back on the menu. :)
@Dan Wilson's 50g was for processed meats though
You're right, it was. I think I must have read it as 'red meat', due to the quote from the IARC.
 
What are the risk figures for 100 grams per day? Or for amounts in excess of that?
After posting, I was actually hoping someone would ask that question. The graph below is from a meta-analysis the WHO report references. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3108955/pdf/pone.0020456.pdf
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It represents the relative risk (RR) over grams of red AND processed meat consumed per day. The black line in the middle is the one to pay attention to. The data described in the authors' words:
There was evidence of a non-linear association of red and processed meats and colorectal cancer (P = 0.03). Visual inspection of the curve (Figure 3) suggests that the risk increases linearly up to approximately 140 g/day of intake. Above that intake level, the risk increase is less pronounced.
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At 140 grams/day, the maximum risk measured by these studies is about 1.3x the normal risk, which means a 30% increase in risk. 30% of the average 5% risk means that those who eat the most red and processed meats will increase their lifetime risk of colorectal cancer from 5% to 6.5%.
 
Do they distinguish between red meat and processed meat? I think it's mainly the processing that is the problem.
 
Do they distinguish between red meat and processed meat? I think it's mainly the processing that is the problem.
A report on the WHO monograph was published in The Lancet and it distinguishes them with the following statement: http://ac.els-cdn.com/S147020451500...t=1504285343_9b25fd7bf28c485ff5fac3812bb0a071
A meta-analysis of colorectal cancer in ten cohort studies reported a statistically significant dose–response relationship, with a 17% increased risk (95% CI 1·05–1·31) per 100 g per day of red meat and an 18% increase (95% CI 1·10–1·28) per 50 g per day of processed meat.12
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I like how that graph shows less risk for 180g/d than it does for 155. :)
Me too. I was just going to say that. Say I eat 165g a day, I can reduce my risk by the same amount by dropping to 145 or RAISING to 180. so that;s an extra rasher of bacon then!!! woohoo!!
 
12. How many cancer cases every year can be attributed to....
How are deaths attributed to general lifestyle or environmental factors (alcohol, air pollution, red meat intake) in the first place? Do they cause specific cancers with specific markers, or are these factors assumed as probable causes only?
 
How are deaths attributed to general lifestyle or environmental factors (alcohol, air pollution, red meat intake) in the first place? Do they cause specific cancers with specific markers, or are these factors assumed as probable causes only?
It depends. In the case of smoking, carcinogens in tobacco cause specific mutations to specific genes. Namely, the p53 gene. http://www.nature.com/onc/journal/v21/n48/full/1205803a.html
In lung cancers, the p53 mutational patterns are different between smokers and nonsmokers with an excess of G to T transversions in smoking-associated cancers.
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In other cases the numbers are estimates with an association and/or mechanism behind it. For example, alcohol causes tissue damage that needs to be repaired. As damaged cells are replaced with new cells, it increases the division rate of the tissue and thus the likelihood that random mutations will accumulate in the stem cells of the tissue which can eventually result in a cancer. It is impossible to tell whether or not the alcohol was the direct cause of a cancer in that case.
When it comes to consumption of red or processed meats, it is all probable cause and a mechanism is not fully understood.
 
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