Is eating meat really as dangerous as smoking… Did somebody use lions to test this hypothesis?

Today’s news papers are full of the latest health scare. The World Health Organisation (WHO) announced that processed meat causes cancer and that red meat might too, leading to some choice news headlines:

Dodgy news headlines

Images sourced via BBC News

So how true are those headlines? Do sausages and bacon top the cancer list? Are they as bad as smoking?

Here are the leading causes of deaths registered in England and Wales in 2013:

Causes of death chart

Heart disease tops the list by far and whilst diet is believed to be a significant contributor, the WHO report is talking specifically about carcinogenics and the link with bowel cancer which is in 8th place.

According to the WHO report, eating 50g of processed meat daily increases the chance of developing bowel cancer by 18%.  Yikes, that sounds a lot. But that’s the relative rate. The absolute rate of getting bowel cancer in your lifetime for the UK as of 2011 was 6% – six out of 100 people are likely to get bowel cancer at some point. The WHO report is stating that people who eat 50g or more of processed meat increase their likelihood of getting bowel cancer to 7/100.

The likelihood of getting bowel cancer regardless of lifestyle is 0.06
If you eat processed meat, your likelihood increases by 18% to 0.07

The survival rate for bowel cancer is 57%

How does that compare with the risk of smoking? According to Cancer Research UK, tobacco is linked to 86% of lung cancers and 19% of all cancers. Eating processed meat is only as bad as smoking in that both have links with cancer. It’s like saying toasters are as bad as the electric chair because both have links with electricity.

The likelihood of getting lung cancer regardless of lifestyle is 0.06 
If you smoke, your likelihood increases by 86% to 0.11

The survival rate for lung cancer is 5%

There were 44.5K new cases of lung cancer and 41.5K new cases of bowel cancer, with over 330K new cases of cancer in total. Let’s visualise the stats:


Still think bacon is as bad as smoking? And the reality is you are still more likely to get cancer for reasons that have nothing to do with smoking, drinking or bacon butties. The leading known cause of cancer? Age.

We have a 50% chance of being diagnosed with some form of cancer during our lifetime and more than one third of cancers are diagnosed in people aged 75 and over. According to Cancer Research UK, more than 95% of new bowel cancer cases were diagnosed in people over 50 years old. Given few people are likely to reach that age on a diet of nothing but sausages and bacon, in many cases it will be difficult to ascertain the specific cause.

Anyway, back to the WHO study which also mentions that red meats (i.e. not processed into burgers, pies etc.) are ‘probably carcinogenic’ and might cause cancer but there was limited evidence.

And there’s the rub. There is limited evidence that meat itself is the actual cause of the increased rate of bowel cancer. Unless you conduct tests using animals that eat nothing but meat you have a lot of variables that are unlikely to be independent*. Processed meats in particular tend to come surrounded or accompanied by bread, pastry and fried potatoes. Sometimes all three manage to find a role on the dinner plate. Now that doesn’t mean the potato or wheat is the bad guy either. But all processed products come complete with a bunch of added chemicals along with mixes of sugars, fats and salt used to pad the product with cheap bulk and flavouring as well as extend the shelf life. It’s a great way for the food industry to maximise their profit margins. Then there’s the cooking at high temperatures using different oils and processes that each create different chemical reactions.

Hence the lion reference opening this post. What we need to do is provide one group of lions with their traditional source of raw red meat. And for another group of lions, substitute red meat with processed meat but none of the processed non-meat extras that humans like to add like chips (aka fries). It won’t help us figure out how much red meat is responsible for lions getting cancer. Trying to force a group to be vegetarians for their lifetime probably breaches animal ethics guidelines given lions seem to prefer eating zebras to grass. But at least it’s a way** of finding out if it is specifically the meat. or the processing of meat that causes cancer versus the processing of food in general. But maybe that would open a can of worms (erm….)

As nutritionist Zoe Harcombe says:

Man is the only species clever enough to make his own food
and the only one stupid enough to eat it.

But the headlines don’t talk about processed food in general. Or that the WHO does also mention that red meat has health benefits. The headlines imprint a dubiously proven but memorable fact – eating meat causes cancer. That sticky piece of information is all that people will remember.

Why the featured image? Another form of dangerous meat. Spot the warning 😉

Image of Rhino art

* The report is not openly accessible meaning I don’t know what 800 studies formed the scientific literature that was accumulated for review by the 22 experts who reached the conclusions. The majority of food health studies that are published and open to public scrutinisation seem to be based on people keeping food diaries which is a dubious scientific approach at best.

** Before anyone writes to complain, I am not really suggesting testing on lions.


Photo: author’s own – Artwork in support of on display at Syndey harbour (image taken in March 2014)

Blog, Data Science, Featured

Join the conversation! 3 Comments

  1. Some additional notes regarding the stats:

    The rates are based on lifetime risk. According to the Cancer Research UK web site as of 27 October 2015, in 2010 the lifetime risk of developing bowel cancer was 1 in 14 for men and 1 in 19 for women, averaging just over 1 in 16 overall (0.0625 aka 6% or 6/100). For lung cancer, the lifetime risk in 2010 was 1 in 14 for men and 1 in 18 for women.

    Age is a significant factor in risk – over 90% of new lung cancer diagnoses are in those over the age of 60 and over 95% of new bowel cancer diagnoses are in those over the age of 50. The older you are, the more other variables your body has been exposed to that will contribute to your risk factor.

  2. Thanks so much for this well done and fair analysis. I was going to continue eating as I usually do anyway, but I feel a little better about it now. I like the way you handle and explain the statistics. I understand them, but I admire your ability to explain it.

  3. Awww thanks so much Dan. Feedback like that is always appreciated.

    Given that all the WHO actually comes up with in their own press release is that red meat ‘might’ cause cancer, ignoring their advice is a good strategy for the majority of people 🙂

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