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Mythbusters: Does eating meat cause cancer?

Time to debunk the myths around eating meat and cancer, and start enjoying this incredibly nutritious food more than ever.

The link between eating meat and cancer

Some "studies" have found that eating meat is bad for our health, particularly when it comes to processed meat and red meat.

Not only has this contributed to the rising popularity of plant-based diets, but it has also led many meat eaters to avoid certain kinds of meat e.g. red meat - in the belief that this is best for their health.

However, much like most studies portrayed and exaggerated in the media, there is far more to these headlines than you would first think.

Let's take a look at what has caused such widely believed misinformation linking eating meat with cancer - and discover the truth behind the headlines.

A closer look at the evidence

There are hundreds of studies which have investigated the effect of eating meat on health. When it comes to the findings about meat causing cancer, there is one report in particular which catalysed panic.

In 2015 the World Health Organisation (WHO) together with the International Agency for Research on Cancer (IARC) published a report around the effect of eating certain types of meat on human health.

Their findings reported on red meat (unprocessed mammalian muscle meat e.g. beef, pork, veal, lamb, mutton, horse and goat) and processed meat (meat which has been transformed by curing, salting, smoking, drying, fermenting or any process used to enhance flavour and preserve the meat).

The conclusions of this report were summarised as follows:

  • The consumption of processed meat "is carcinogenic to humans" (Group 1)
  • The consumption of red meat "is probably carcinogenic to humans" (Group 2A)

The groups mentioned are used to categorise how much of a cancer hazard substances are, based on scientific evidence. Group 1 indicates the highest risk whereas Group 2A indicates a 'probable' cause of cancer and Group 2B indicates a 'possible' cause of cancer.

The findings were based on an evaluation of over 800 studies. They found that processed meat was linked to increased risk of colorectal cancer and stomach cancer, whilst red meat was linked to increased risk of prostate cancer and pancreatic cancer.

Flaws in the Studies

For those who are used to doing their own research beyond the mass media announcements and headlines, you may have noticed something crucial about the summary of findings.

That's right, the cancer causing effect is described as 'linked to' eating red meat and processed meat. Delve into the published study further and you will find this phrase together with 'associated with' used throughout to describe the results.

Put simply, 'linked with' and 'associated with' do not imply causality. Without causality, there is no cause and effect - and so it is impossible to say that the observations for increased risk of cancer were caused by either red meat or processed meat.

Let's take a look at some of the meaty issues with the 2015 IARC report.

 

1. Confounding factors & Healthy-user bias

    There are of course several diet and lifestyle choices which affect individual cancer risk. Smoking status, activity levels, alcohol consumption and what we eat are some of the main examples. It is a combination of all of these together with the important factor of genetics which dictates overall risk for most cancers.

    This is important because studies have shown that those who eat the most red and processed meat typically smoke, drink more alcohol, exercise less and have a poorer quality diet - higher in refined grains, sugar and junk food. Needless to say that a combination of these could significantly increase cancer risk, rather than red meat being the sole cause for the heightened risk.

    Confounding factors can also influence positive health outcomes. For example, vegetarians are far more likely to engage in a healthy lifestyle which is physically active, limits junk food and avoids alcohol and smoking - in short, making significant intentional behaviours which contribute to the 'healthy-user bias'.

    As these are all hugely influential factors for overall health, observations finding that the vegetarian population have better health outcomes on average could not imply that the reason for this is plant-based food - as there is so much else contributing to the equation.

    To really prove cause and effect, you would need to find 2 large populations whose diet and lifestyle were more or less the same aside from their meat consumption. Needless to say, this would 'probably' be very unlikely!

     

     

    2. Reverse causation

    Something else to consider with 'associations' and findings which show one thing is 'linked with' another is reverse causation. This is a fancy term which means that even if there is a statistical link between two factors, it is not always evidence that one causes the other.

    For example, if you were to hold your breath then your oxygen levels would drop. This would be statistically significant and easy to prove. However, low oxygen levels would not be the cause of someone holding their breath. The cause would be the person choosing to hold their breath, and the effect would be low oxygen levels.

    In other words, finding a link between two factors is not enough to prove cause and effect when the other mechanisms at play are not well understood - let alone when there are multiple confounding factors to consider.

     

    3. Self reported recall inaccuracies

     

    Another huge obstacle to obtaining accurate data on food consumption and disease is recall of food diaries.

    Self-reported food intake is the usual source of data for observational studies, where participants recall what they have eaten and document this themselves. As it is simple and inexpensive, this method of data collection is favoured in the majority of studies.

    However, self-reported food intake is vulnerable to inaccurate estimations, forgetfulness and a tendency to lie about or exaggerate food intake due to feeling self-conscious.

    Studies on these studies (!) have shown that traditional self-reported dietary instruments are prone to inaccuracies and that new approaches are needed to reliably assess the impact of diet on health.

    Overall, the nature of research into diet and health means that it is very difficult to overcome obstacles such as confounding factors, reverse causation and self-reported data collection. As the 800 studies analysed in the 2015 WHO report were mostly observational, their findings cannot imply cause and effect for this reason.

    What do other experts say about meat and cancer risk?

    When the IARC published their report on processed meat and red meat intake being linked to increased cancer risk, it was received with difficulty by scientists and food researchers worldwide. Here is what some notable scholars in the field had to say.

    • A 14-member international team of scientists led by Dalhousie University, Canada - "Based on the research we cannot say with any certainty that eating red or processed meat causes cancer."

    • Walter Willett, professor of epidemiology at Harvard School of Public Health (and, interestingly, an advocate of a plant-based diet) - "This report has layers of flaws and is the most egregious abuse of evidence that I have ever seen."

    • Bradley Johnston, associate professor of community health at Dalhousie University, Canada - "Among 12 randomised control trials enrolling about 54,000 individuals, we did not find a statistically significant or an important association in the risk of heart disease, cancer, or diabetes for those that consumed less red and processed meat."

    Overall, the possible link between meat and cancer risk should not be ignored - but certainly warrants further investigation. Furthermore, the notorious unreliability of self-reported dietary intake data should be a huge consideration in any future research.

    As it stands, the evidence provided by the IARC is arguably not strong enough to warrant modification of dietary intake recommendations - especially on a population level. 

     

    Not all meat is created equal

    Something which should be a consideration when choosing to eat or avoid meat is the type of meat in question. Like all food groups, 'meat' is an umbrella term encompassing a multitude of meat varieties. Each of these will have their own unique nutritional profile, benefits and sometimes health risks.

     

    Processed Meat

    One thing which we can agree on with the 2015 report is that heavily processed meat consumption is best limited, or avoided altogether.

    Processed meat includes ham, bacon, salami, sausages - and any meat which has been processed to enhance flavour or extend shelf-life. As with any food product, the more it is processed the more hidden nasties are added, and the more alien it becomes to our bodies - having a potential negative effect on health.

    One particular concern with processed meat is nitrates and nitrites. These are chemicals which are added to processed meat to keep them fresher for longer. When consumed, these substances are converted to N-nitroso compounds or NOCs, which have been found to increase cancer risk.

    As nitrates and nitrites are not allowed in fresh meat preparations, this could explain why the IARC report found that processed meat posed a higher cancer risk than red meat.

    Overall, we are firm believers that natural food just as our ancestors ate is the best route to optimal health. Anything which has been tampered with, added to, genetically modified or otherwise processed is best avoided to reduce the risk of poor health as a whole.

    However, it should be noted that some processed meats are minimally processed e.g. bacon produced without nitrates - and likely much safer to consume than others which are heavily processed e.g. mechanically recovered cured ham.

    Grass Fed, Organic and Unprocessed Meat

    On the other hand, grass fed and certified Organic meat is about as natural and unprocessed as it gets.

    When choosing to eat meat, an interesting consideration is what the animal eats and how this can impact our own health - as part of our diet and the effect of the food chain.

    Grazing animals are allowed to roam free on the land and eat the diet Mother Nature intended - without ultra-processed, GM grain-based feeds packed with preservatives or artificial ingredients, and without being pumped with hormones and preventative antibiotics.

    Not only is this a farm to fork solution, but attention is paid to the animal's diet throughout its lifecycle - with a focus on how the end product can impact health.

    The truth about red meat

    When you've got your head around the fact that there is limited (and quite frankly) weak evidence to show that red meat has cancer causing properties, you can instead spend your reading time learning about the strong and undeniable evidence that red meat is in fact a health food and is good for us!

    Red meat such as beef, lamb, venison and pork is actually a nutritional powerhouse which we consider to be a superfood.

    The vast spectrum of bioavailable nutrients you'll find in red meat includes B vitamins, minerals, antioxidants, choline, conjugated Linoleic acid (CLA), omega-3 (albeit wild-caught oily fish is a far superior source) and all 9 essential amino acids.

    Studies have also found that grass fed red meat in particular has a better nutritional profile than its grain fed counterpart (albeit not necessarily as much as you might think). You can learn more about red meat nutrition and the benefits of grass fed meat in our articles below.

    👉 What conventional dietitians get wrong about beef nutrition

    👉 Is grass fed meat really worth the hype?

     

    A word of caution for vegan 'meat' replacements

    Meat 'replacements' made from plant-based ingredients are often marketed to be the healthier, greener and a more ethical choice when compared with meat.

    However, compared with good quality, unprocessed and ethically raised meat - there is really no comparison. Furthermore, vegan meat replacements are arguably more processed than processed meat and require a significant amount of inputs with little to no regeneration/carbon sequestration associated. 

    To get something like a mushroom, soy bean or other plant-based food resembling meat in appearance, taste and texture - a whole load of added ingredients are understandably needed.

    That means that most vegan meat replacements will contain a) no nutritious meat (of course), and b) several added ingredients including artificial colours and flavourings, grains, seed oils, preservatives and added refined sugar & refined salt. So whilst plant-based meat alternatives may be seen as a better choice for the animals (a separate topic for another day!), they certainly aren't for us humans.

    Always be cautious when replacing nutritious meat in your diet with heavily processed, artificial and simply unhealthy plant-based alternatives. Instead, it is much better for vegans and vegetarians to get their protein from natural, whole foods instead.

     

    The verdict:

    Eating meat does not cause cancer! Choosing quality grass fed meat which is as natural and unprocessed as possible will contribute to a healthy and nutritious source of protein, vitamins and minerals to your diet.

    Reducing your intake of red meat based on weak observational evidence could in fact be detrimental to your health. Processed meat (like all processed food) should be minimised in the pursuit of optimal health but the occasional enjoyment of minimally processed meat is likely not harmful to health.

     

    References

    • https://www.acpjournals.org/doi/10.7326/M19-1621
    • https://www.iarc.who.int/wp-content/uploads/2018/07/pr240_E.pdf
    • Public Health EnglandThe Eatwell Guide. London, UK: Public Health England; 2016
    • https://link.springer.com/article/10.1007/s13668-013-0043-5
    • https://pubmed.ncbi.nlm.nih.gov/25969395/
    • https://www.frontiersin.org/articles/10.3389/fnut.2020.00090/full
    • https://www.theguardian.com/food/2019/sep/30/research-red-meat-poses-no-health-risk
    • https://www.researchgate.net/publication/264375804_Nitrite_and_nitrate_in_fresh_meats_A_contribution_to_the_estimation_of_admissible_maximum_limits_to_introduce_in_directive_952EC

     

    All information provided on our website and within our articles is simply information, opinion, anecdotal thoughts and experiences to provide you with the tools to thrive.

    It is not intended to treat or diagnose symptoms and is definitely not intended to be misconstrued for medical advice. We always advise you seek the advice of a trained professional when implementing any changes to your lifestyle and dietary habits.

    We do however recommend seeking the services of a trained professional who questions the conventional wisdom to enable you to become the best version of yourself.

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