…on WHO, Bacon and Cancer

sizzling-baconSo the World Health Organisation’s International Agency for Research on Cancer has apparently classified bacon as a highly dangerous cancer-causing menace which must be avoided at all costs, and they are pretty sure all red meat probably also causes cancer in anyone who so much as thinks about it, and therefore in order to have any chance of staying alive we must all immediately become vegans (preferably a level 5 vegan at that). At least that seems to be the general view being promoted by the mass media in general, and by a great number of the more evangelical vegans across social media right now.

“WHO says eating bacon is as dangerous as smoking and alcohol” scream some headlines, whose articles go on to predict all manner of dire consequences for those foolish enough to dare to eat bacon. “And red meat probably also causes cancer” they go on to announce.

So is that it for bacon, sausages and red meats in general? Must we avoid these at all costs in order to attempt to remain alive?

Well, no. As always, the reality of the situation is rather less alarmist when one takes a few moments to look at what WHO IARC actually said.

Before we examine their findings in a little more detail and place things into their proper context, it is first important to take a step back and understand IARC’s cancer categorisation. IARC place every item they test into one of 5 different categories according to their risk of causing cancer –

  • Group 1 – Known carcinogen in humans.
  • Group 2A – Probably carcinogenic in humans (sufficient evidence in animals, limited evidence in humans)
  • Group 2B – Possibly carcinogenic in humans (insufficient evidence in animals, limited evidence in humans)
  • Group 3 – Unknown cancer risk (inadequate evidence in animals, inadequate evidence in humans)
  • Group 4 – Probably not carcinogenic (evidence in humans and animals suggests no risk)
    There is currently only 1 item in this list, the organic (in its true chemical sense) compound Caprolactam

It is important to note that the IARC classifications tell us absolutely nothing about the amount required to cause risk, nor the level of increased risk, simply whether they can pose a risk.


Life is full of risks. Some are avoidable, some are unavoidable. When deciding whether to take steps to avoid a given risk, there are two key factors to take into account –

  1. The level of risk (sometimes called the impact of the risk)
  2. The likelihood of risk (otherwise known as the probability of the risk)

It is the combination of these two factors which is important when assessing a risk. This combination is usually called the “composite risk index” and can be calculated through the following formula –

composite risk index = impact of risk x probability of occurrence

The impact of the risk is commonly assessed on a scale of 1 to 5, where 1 and 5 represent the minimum and maximum possible impact of an occurrence of a risk.

The probability of occurrence is also commonly assessed on a scale from 1 to 5, where 1 represents a very low probability of the risk event actually occurring while 5 represents a very high probability of occurrence.

The composite risk index can take values ranging from 1 through 25, and this range is usually arbitrarily divided into three sub-ranges – Low, Medium, High.

For example, a large asteroid colliding with the Earth would pretty much wipe us out and so would score a 5 on the impact of risk. However, the likelihood of it happening during our lifetime or the lifetime of our children or grand children is infinitesimally small, and so the probability would score firmly as a 1 (if not smaller). Which gives a composite risk index of 5, or Low. Thus it is not something which preoccupies most of us on a daily basis.
Walking outside in the rain without a coat or umbrella certainly gives a level 5 in terms of probability of getting wet, but the level or impact is definitely a 1, so again is a very low risk activity overall.
Driving while under the influence of alcohol would present a significant probability of a bad outcome, and the level of that could well be high, resulting in a composite risk index in the High range – which would be why it is against the law to drive in such a state.

So where does that leave us in regard to eating bacon? WHO IARC has stated it is a known carcinogen, so in terms of the risk of developing cancer – specifically colorectal cancer (which, in Europe, kills around 1 in 3 of those who contract it); that’s certainly a high level of risk. And this is the area on which the scaremongering articles have focused.

But what about the other part of the equation, namely the probability? To understand the impact here, we need to look at the figures. For a “standard” person who does not eat bacon (or other processed meats), 64 people out of 100,000 develop it in any given year. For someone who consumes 50g of bacon every day, that becomes 72 people out of 100,000. Or, to put it another way, eating 50g of bacon every single day increases your likelihood of developing colorectal cancer by 8 in 100,000 – 0.008%. Extremely small by anyone’s standards.

Which means when we take both the level AND the probability into account, the overall composite risk index is firmly in the “Low” category.

Remember, all that WHO have done is classify the level of risk, NOT the probability. That is all their 5-category scale does.

Yes, bacon is classified as Group 1 – known carcinogen, which is the group which includes (as the media delight in reminding us) alcohol and cigarette smoke. But that group also includes areca nuts, leather dust, wood dust, sunlight and Chinese style salted fish!  Presumably those seizing upon the classification to demand we all stop eating bacon will also demand we all stop receiving sunlight?

in the world 34,000 people die every year from a high processed food diet, compared with one million deaths because of alcohol.” – BBC News website

To Eat Bacon Or Not To Eat Bacon?

The reality is that unless you plan to binge-eat bacon every single day of your life, the increased risk of developing colorectal cancer through the consumption of processed meats is extremely small. If you eat 50g of bacon every day for the next 50 years, you would have an increased risk of developing colorectal cancer of 0.4% over those 50 years which, in Europe currently, equates to a risk of death of 0.12% over those 50 years.
Not exactly the greatest risk facing us, especially when you consider that requires eating 50g every single day.

If you want to eat bacon, eat it; if you don’t want to eat it, don’t eat it. As with all things, moderation is the key.

The Bigger Picture

There is more to this than just whether or not to eat bacon.
The near-hysteria in some circles around the recent WHO news highlights several important points which should be borne in mind any time you read pretty much anything (including this post) –

  • When you read an article, always ask yourself if all of the information has been presented
  • What other sources of information are there, and how to they fit? Remember to seek out concrete information, not just someone’s opinion.
  • Consider who is sharing the information – do they have an agenda?
  • If you plan to share something because it agrees with your view, have you made sure what you are sharing hasn’t missed something? Confirmation Bias is a dangerous trap into which to fall!

If you really want to test the validity of what you are reading, a great way is to attempt to disprove what has been presented (this is a key part of what is known as the scientific method) – either you will discover that it was false (in which case you have avoided believing something untrue), or you will have been unable to disprove it and thus gained a deeper understanding of the topic and be accepting something which has a much higher likelihood of being true. Either result is a good one.

Unfortunately it is all to easy for us to readily accept something uncritically just because it agrees with what we already believe, and to dismiss out of hand anything which disagrees with our own position – an easy way to figure out if you are falling into that trap is to consider how you react when you share your information and others then disagree with what you have said. Do you react by getting annoyed with them for disagreeing? Then you may well be guilty of confirmation bias!

Get the debate started here!