Does Red Meat Cause Cancer?
We were going to write a full article here, inclusive of research links and citations. Until we stumbled (in said research) across the always fabulous Dr Sarah Ballantyne’s article which basically did our job for us.
However, it was rather lengthy and science-y. So instead of rewriting it, please read her wonderful work if you’d like the depths, but here we’re going to simplify and state the facts as the well-informed in the Paleo community see them when it comes to red meat.
For research studies and further reading – do see The Paleo Mom’s article which, as always, contains exemplary referencing!
Many people in ‘alternative’ health communities (i.e. those not backed by Big Pharma and/or medical establishments) like to criticise research studies for being a) biased by funding, b) using flawed methodology, c) skewed in terms of how the data acquired is analysed, d) flawed because of the limitations of the populations included in the study or e) failing to factor out some variables. Or a combination of all of the above.
There is no doubt that in scientific studies there can be an enormous amount of bias, or publishing pressure and there is also the notorious phenomenon of failing to publish studies that show unexpected (by which we mean ‘unwanted’) results. This occurs especially in the field of nutrition research, in which hard facts and excellent methodology is really hard to come by simply because there are so many variables and factors to control for.
Many in the Paleo community who seek to dismiss the bewildering array of studies linking red meat to cancer typically do so founded on the arguments above.
Because they are so devoted to their carnivorous consumption, they claim that factors such as ‘meat quality’ and ‘the quality of the remainder of the diet’ are variables that are not taken into account when studies link meat to cancer. They claim that there is an ‘healthy user bias’, in that people who are trying to be healthy veer towards vegetarianism because of the mass media view of this diet. This means that in epidemiological studies the data can be skewed because the people who are exercising, avoiding inflammatory foods and eating nutrient-dense diets filled with vegetables also happen to be avoiding meat because they’ve been told it’s bad for them. Thus meat consumption inadvertently becomes associated with poorer health outcomes simply because those who consume meat tend to do so in the context of otherwise unhealthy lifestyles.
Another Paleo argument dismissing the ‘red meat is bad for you’ claims revolves around the quality of the meats studied. The argument goes that the meat used or studied in scientific trials tends to be factory-reared, grain-fed and of poor nutritional value. This will undoubtedly affect the results of trials because the nutrient and fatty acid profile of such meats is certainly not up to par with wilder, grass-fed, naturally raised animals.
And yes, there is an element of truth to both of these arguments.
But we’re sorry to say to the Paleo community that these are poor retaliations against the ‘red meat causes cancer’ studies. Because actually, there are a lot of studies linking red meat to cancer, and many of them are well designed enough to not only factor out the ‘meat quality’ and ‘healthy user’ variables but also to attempt to glean data that assesses mechanisms and biological interactions, rather than just studying short- or even long- term health outcomes.
Why Red Meat Really Does Cause Cancer
What? I hear you cry – are we suddenly all to put down our bacon? Um… not really… but not just because you like it. There are real, deeper scientific reasons that the cancer arguments both have merit, but also might be not the whole story:
The question of meat quality is interesting. Poor animal husbandry may produce nutritionally inferior meat and additionally the antibiotics and hormones used to treat the animals may result in an excessively toxic end product. That said, the toxin load of any animal (including humans) is normally deposited in its fat cells where it is ‘safer’ and presents less of a burden to the body. This means that a lot of the toxins from poorer quality meat are found in the fat and not the protein.
And yet the part of the meat that is linked, in several ways, to causing cancer (not just cellular and inflammation issues from oxidised fat but actually carcinogenic compounds which go on to cause cancers) is actually found in the meat protein. Most specifically – in the haem (heme) protein, i.e. the red bit that you might think of in the context of haemoglobin, or red blood cells. Whilst poorer quality meat might have nutritionally less rich proteins and amino acids, that is not a factor in how red meat protein causes cancer.
Haem is the iron-containing compound which makes red meat red. It has the unfortunate side-effect of binding to cells in the digestive tract which metabolise it into compounds which are not just quite toxic – they’re actually carcinogenic. This is not equivocal or small, with this human study showing that in men there is a statistically significant association of the haem protein’s capacity to not only mechanistically bind to human colon cells but to do so in a way that increases incidence of colon cancer.
There is more damning evidence against red meat, however. One potential problem is found in the link between something called TMAO and red meat consumption. TMAO has been strongly linked to both cancer AND heart disease because it promotes the cardinal sin of all health outcomes: it promotes inflammation. This is definitely serious and worth considering because meat proteins have a high capacity to be converted into TMAO due to the concentrations of L-Carnitine, from which TMAO originates. There is an argument against this TMAO debate which is that TMAO is actually present in its highest in some oily fish, and nobody is saying fish cause cancer (yet!). But whether it comes in the form of meat or fish, TMAO is something to consider in terms of overall cancer burden to the human body. It is, therefore, another reason to be wary of red meat.
And lastly, there’s the way we like to cook our meat – by grilling and charring the outsides to get that beautiful caramelisation and texture. We all know that burning food causes cancer because we all read the toast article, right? And yes, there is a lot of science about the dangers of the compounds (also known as mutagens) which are given off when heating food at high enough temperatures to cause blackening. These compounds vary depending on whether they come from the cross-reaction of the meat’s amino acids with the heat source or whether they arise as the fat from the meat source is oxidised by the heat. Nevertheless it is clear that heating any food (including fat, but that’s another topic) to high temperatures creates reactions both within and on our food which have been shown to be carcinogenic, i.e. cancer causing.
Quite how much these are cancer causing is an open question – largely because measuring the charring of meat and the levels of these compounds eaten is tough. There is actually more evidence for the argument that oxidised and rancid fats (including plant fats) are more toxic and damaging to humans. But this article isn’t about that, so if you want more on fat oxidisation we’d highly, highly recommend “Deep Nutrition: Why Your Genes Need Traditional Food” by Cate Shanahan and we are working on our epic rundown of fats, which will be coming soon…
When Red Meat Doesn’t Cause Cancer
The real issue with every reason that red meat might create carcinogens and/or toxins and/or inflammation etc. etc. is that it looks at red meat in isolation – metabolically examining pathways of protein breakdown and reactivity. And though we make the argument everywhere on this site that the mechanism of food interactions underlies our scientific theory, this is a classic case where mechanism has been conflated to equal cause without recognition that more elements are at play within the human diet.
In truth, we eat meat as PART of our diet. More than that, inside our bodies are mechanisms specifically designed to handle toxins ingested and produced as part of living in the world. Toxicity is a byproduct of being alive, and our bodies have really good ‘clean-up’ machines – also known as the liver. There may be many more toxins now than there used to be, and there are many more incidences of cancer, but there isn’t more red meat in our diet than previously. In fact, our meat consumption is progressively trending downwards globally. One possible explanation is that meat forms part of an overall toxic burden that is just too high for our bodies to process.
Possibly, but let’s dig into the mechanisms again – this time of detoxification – to understand why the Paleo diet specifically is not inherently carcinogenic.
When it comes to the cytotoxic compounds produced by haem and the carcinogens produced when heating meat to high temperatures, there is a wonderful process in which these compounds can be offset. This simply requires the presence of a wonderful nutrient called chlorophyll. Whilst the study linked to here is a rat study, don’t be fooled – a large majority of the studies done to prove the haem/colon cancer connection in the first place were rat model studies.
So this is a big piece of information to bear in mind when reading isolationist and reductionist nutritional science. Life does not exist in a vacuum.
In this case, the things that make meat red cancerous can be offset by the very thing that makes plants green. More than the chlorophyll argument, the science also states that cruciferous vegetables such as broccoli and cauliflower completely alter the body’s metabolism of carcinogens. So eating huge amounts of dark green leafy and cruciferous veggies (which is always recommended when we talk about Paleo nutrition) means that a Paleo diet which is supposedly rich in red meat (and therefore cancerous) contains the antidotes, alongside the poison.
As for the TMAO – there is growing evidence that the production of L-Carnitine into TMAO is helped along by a specific gut bacterial species. That species tends to be higher in those who consume grain products. As we already know grains aren’t consumed on a Paleo diet – and even if you’ve made reintroductions of small amounts of rice/oats you aren’t basing your plate around grains and cereal. This means that for those on a proper Paleo diet the species of bacteria that metabolises L-Carnitine into TMAO is lower, so conversion into TMAO is reduced and inflammation potentials of red meat (and fish for that matter) all but disappears.
Complex Human Physiology – Why “Hard Science” Isn’t Always the Be All & End All
The best way to study nutritional interventions and to scientifically understand cause and effect of certain nutrients is to examine them in isolation.
The worst way to think about human nutrition, diet, food consumption and metabolic effects is in isolation.
The human body works in concert and the Paleo diet is constructed such that it basically covers all of the bases to allow every interlaced function to operate optimally and efficiently.
By including certain foods the Paleo template provides us with the ability to buffer the toxic byproducts of others. Avoiding certain foods boosts the ability for our bodies to eat some foods which contain a little higher percentage of anti-nutrients. And being generally attentive to nutrient density provides Paleo dieters with the health and the reserves to encounter environmental and emotional stressors and have the metabolic capacity to weather and recover from the physiological effects that come from these.
Whilst we’re sure that those who look to websites on nutrition (particularly their ‘Deeper Science’ sections!) are seeking hard facts and peer-reviewed literature as evidence, the reality is that the human body is an orchestra of complexity on which science is sometimes a poor measuring stick.
You may have heard reference to the human body being a ‘chemistry set not a maths equation’… but even that analogy falls short of describing the integrated and interdependent functions which constantly interact within the biofeedback loops of being alive.
With the red meat debate there is no doubt that, as with all things in human consumption, excess is going to tip the balance towards problems and away from health. As with all things in human nutrition, what ‘excess’ means in the individual is going to be highly dependent on many factors, not least of which is the number of other burdens within someone’s diet AND lifestyle, their genetic inheritance and also the measures they have in place to offset all of these burdens, stressors and toxins.
It is not enough for us to rely on the science of mechanisms and pathways. It is about recognising that most of human biology is based on dualities and on ebb and flow. I have witnessed this countless times in the genetics and functioning of my clients and myself. More often than not I will observe a ‘weakness’ in one pathway is offset by a different mutation in another. I see the human body as one of those weighted clowns on a bosun ball – always attempting to find ways to tip itself back to balance. As an organic and non-static system there is typically always a bit of give and take – and the red meat example illustrates this perfectly.
Red meat does create carcinogens which contribute to toxic burdens which can create tumours which can lead to cancers. However, that line is not linear and it has many, many rate-limiting and derailing steps along the way, any one of which will divert the ‘potentially cancerous’ to become an ‘easily eliminated toxin’.
The one thing the body needs more than anything in order to protect itself from any outside (and internal) threats is nutrients. We may not always know which ones, in which ratio and when – but you can’t go very far wrong with supplying enough of all of the basic nutrients and rest.
When over-taxed the body will burn through more nutrients more quickly.. and the Paleo diet and lifestyle (and its AIP offspring) are constructed around the deep recognition of the fact that life is demanding and nutrients are on high turnover – especially on those with any illness or immune system dysfunction or in those for whom life is excessively stressful.
Eating from the nutrient dense, vegetable AND animal protein rich Paleo template means that the body is being provided with everything it needs to do what it is designed to do: deal with threats and stay alive. As far as red meat is concerned it contains way too many nutrients and amino acids to be off the table. Red meat does not cause cancer. It especially does not create damage to the human physiology when consumed in the context of a nutrient-dense, phytonutrient and polyphenol rich diet… hence, Paleo.