Today, 26th October 2015, the World Health Organisation declared the consumption of red meat as “probably carcinogenic to humans, based on limited evidence that the consumption of red meat causes cancer in humans” and declared processed meat as “carcinogenic to humans, based on sufficient evidence in humans that the consumption of processed meat causes colorectal cancer.” The red meat association was observed mainly for colorectal cancer.
“The experts concluded that each 50 gram portion of processed meat eaten daily increases the risk of colorectal cancer by 18%.”
From the headline “carcinogenicity of consumption of red and processed meat”, we’re already down to colorectal (bowel) cancer and “probably”.
So do we need to stop eating red meat and/or processed meat? Let’s dissect the headline more accurately:
1) Where this data comes from
The gold standard of evidence is a meta-analysis of randomised controlled trials – pooling together studies where an intervention was matched against a control group to see what impact A had on B. As far as I am aware, no intervention studies have ever been done testing the impact of 50 grams of processed meat per day as an isolated intervention, or any amount of processed or red meat as a sole intervention for that matter.
We are thus looking at observational studies. This is where a large group of people (e.g. the Nurses’ Health Study or the Health Professionals Follow-up Study) are asked loads of questions and given health tests (blood pressure, weight, height, cholesterol ho ho etc) at the start of the study. This is called the baseline. These people are then followed for years to see what conditions they go on to develop.
Researchers then look at the data to try to see patterns. No pattern = no journal article, so look hard! They may observe a pattern between people who consume processed meat and people who go on to develop bowel cancer. This is then reported in a journal article and it is all such articles that have been reviewed by the World Health Organisation.
The first point to make, therefore, is that all of this is based on notoriously unreliable dietary questionnaires. Many ask what you ate yesterday or over the past 7 days. Here’s the European Prospective Investigation into Cancer questionnaire, one of the best possible questionnaires, as it asks for food intake over the past year. How accurate do you think yours would be?
2) One’s diet vs. one food
By singling out red meat/processed meat in this way, the whole diet and lifestyle of a person is not taken into account. There is a world of difference between the health of a burger/hot-dog/ketchup/white bun/fizzy drink guzzling couch potato and a grass-fed-steak eating/CrossFit/six-pack Paleo specimen.
As I showed in this blog, the baseline for the processed meat eaters showed that they were far less active, had a higher BMI, were THREE TIMES more likely to smoke and almost TWICE as likely to have diabetes. This makes processed meat a MARKER of an unhealthy person, not a MAKER of an unhealthy person.
Even if all the smoking/exercise/other conditions baseline factors are adjusted for, there is no possibility of adjusting for all the dietary factors that make up the couch potato vs. the Paleo buff. The whole diet is not adjusted for when the one line (meat) is targeted.
3) Real food vs. processed food
I’m a real foodie. I pretty much spend my life writing and talking about real food and the nutrition it contains. I am the first to say “Do eat real food; don’t eat processed food” and I include processed meat as processed food – something to avoid. However, this WHO report describes processed meat as “meat that has been transformed through salting, curing, fermentation, smoking or other processes to enhance flavour or improve preservation.”
As Peter Cleave, Surgeon Captain, (1906-1983) said: “For a modern disease to be related to an old fashioned food is one of the most ludicrous things I have ever heard in my life.” To think that real meat, or meat preserved in natural ways, is bad for us is ludicrous. 1) You’d have to explain how we survived the past 3.5 million years, since Australopithecus Lucy first walked upright; especially how we survived the ice age(s). 2) You’d have to explain why all the nutrients we need to live (essential fats, complete protein, vitamins and minerals) are found in meat if it were trying to kill us at the same time.
Meat needed to be naturally preserved with salting, curing, drying, smoking etc or we would have needed to binge on the kill and risk dying of starvation before the next kill. The WHO report should have separated traditional ways of preserving meat from modern manufactured processing (where sugars and chemicals are added – just read the label). Similarly – if there is any harm in red meat, it will be because manufacturers have got involved and fed the poor animals grains, which they cannot digest and then pumped them with drugs to medicate the resulting illness. (Chris Kresser presents the view on nitrates here, if you’re interested).
This should be a call to action to get back to your butcher, know him/her by name, know where your meat comes from, know how s/he prepares bacon & hand-made sausages and enjoy the health benefits of real food while supporting the grafters who provide it.
4) Association vs. causation
Even allowing for the weakness of observational studies, and the unreliability of dietary questionnaires, and the notion that food consumption can be a marker not a maker of health, and the whole dietary intake that has not been taken into account and the ignorance of the chasm between real and processed food, this is still association, not causation.
I always wish that these huge and expensive studies would ask what colour socks the participant is wearing. I bet I could find an association between red sock wearing and one type of cancer if I looked hard enough. Would the headline be red socks cause cancer?!
5) Relative vs. absolute risk
The press release headlines with “each 50 gram portion of processed meat eaten daily increases the risk of colorectal cancer by 18%.” Crikey. 18%! Put that bacon sarnie down now (see – don’t blame the bacon for what the white bread & ketchup did!) This, however, is the game that all of these observational study research press releases play and it’s disgraceful scare-mongering.
Shall we look at the absolute risk?
Cancer Research UK has terrific statistics on all types of cancer. I’ve just looked at the UK. They do have data for other countries if you want to do your own rummage. The incident rate for all people in the UK, age-standardised (you pretty much won’t see bowel cancer before the age of 50 – look at the age data), in 2011 was 47 per 100,000 people.
47 per 100,000 people.
You would need to know 2,128 people, including enough older people, to know 1 person who developed bowel cancer in the UK in 2011.
Now – let’s do that relative vs. absolute risk thing.
Assuming that everything the WHO did had been perfect and that there really was an 18% relative difference between those having 50g of processed meat a day and those not (and assuming that nothing else was impacting this), the absolute risk would be 51 people per 100,000 vs. 43 people per 100,000.
Now where’s the bacon and egg before my CrossFit session?!
The likely harm of this report:
The Lancet article does at least have the decency to mention the nutritional value of red meat: “Red meat contains high biological value proteins and important micronutrients such as B vitamins, iron (both free iron and haem iron), and zinc.” That’s still a bit of an understatement. Try both essential fats; complete protein; and the vitamins and minerals needed for life and health.
What will be the consequences of this report scaring people away from real meat? It takes approximately 250g of sirloin steak to get the daily 10mg of zinc; over a kilo of the same steak to get the recommended daily iron requirement – and in the right form for the body. How about over 20 eggs to get the same iron intake? Still in a useful form to the body. Or 4.5 kilos of brown rice to get iron in the wrong form for the body?
What do I take from this report? There is a heck of a lot of bad science coming out the World Health Organisation, an organisation that should know better, but then there have previous cases of not knowing better.
Nothing has changed from my fundamental belief that human beings should eat real food (especially grass-fed, naturally reared meat and naturally preserved meat). Avoid processed food, including meat processed by fake food companies. And take every observational study that doesn’t know these five points above with a hefty pinch of salt.