So last week’s article discussed the epic “Meat and Milk Debate” in which I tackled the debates around farming, agriculture, Veganism and the animal consumption on a Paleo-style diet. In that post, I alluded to an ‘Is Red Meat Good For You?’ post that was in the pipeline. Herewith, please find said deep dive into red meat, cancer, nutrition, Paleo diets and all of the furore around eating animals from the human physiology (as opposed to the ethical) perspective.
The best person to go into the science and the hoopla around Red Meat and Cancer is always going to be Dr Sarah Ballantyne, of The Paleo Mom. If you’d like the depths around evolutionary dietary selections and how people have evolved as omnivores read her article here, but there’s also a fundamental component to modern consumption of red meat which must be addressed – the link between red meat and cancer.
Dr Ballantyne does go into the research studies surrounding this, and gives some lengthy science-y explanations on a Paleo Mom website article. Here I am going to not only review the data she discusses but also talk about how the act of doing nutritional science makes us forget that there is actually an art to being a human. Nutritional decisions often need to be based on the latter of these because human bodies are not simple cause-effect machines.
But first, the basics:
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 I’m 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 high 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 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 oxidation I would highly, highly recommend “Deep Nutrition: Why Your Genes Need Traditional Food” by Cate Shanahan.
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 I am a big believer in understanding the mechanism of food interactions in order to comprehend the way different foods interface with the human body, 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 within 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 grains aren’t consumed on a Paleo diet, even if you’ve made reintroductions of small amounts of rice/oats as many modern Paleo advocates do, whole plates aren’t based 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.
Food, Targeted Nutrients and Diets – and Why All Three Are Different
This is actually going to form a jumping off point for a future blog – all about treating patients not paperwork – and yet another article about how bodies are complex and targeted nutrition is a poor strategy. If you want the ultimate article on that for right now, please do read Mark Sisson’s latest ‘self-quantification is nonsense’ article over on his Mark’s Daily Apple blog.
For now, however, let me stick to red meat and reductionism.
The three elements of healthcare mentioned in this section’s title are actually three different things. Food is the single foods we eat, targeted nutrients are the vitamins, minerals and amino acids or fatty acids present in these individual foods and the “diet” is the combination of all the foods that we take in over the course of days, weeks, months and lifetimes.
Because information is literally free in the current internet age there are a wealth of factoids out there in the ether which dig down into details of diet. They are, a lot of the time, based in truth – but there is always an element of ‘simplification’. The issue comes because the best way to study nutritional interventions and to scientifically understand cause and effect of certain nutrients is to examine them in isolation.
However, the worst way to think about human nutrition, diet, food consumption and metabolic effects is in isolation. Because you don’t just eat nutrients – you eat foods, and you eat a whole diet worth of nutrients. You also put those nutrients and foods into a whole cacophony of metabolic processes, some determined by genetics, some determined by lifestyle factors and others based on current stress, emotional states and overall energy levels. This red meat example is a classic example of how the extreme conclusion neglects to account for the mirky, grey area, middle ground in which most of biology tends to sit.
A chief complaint about the modern media when it comes to food headlines is that ‘every other day they tell you some other food causes cancer’. The common conclusion is that none of the stories are true. However, I would wager that, in certain contexts, many foods really can cause cancer, and heart disease, and liver failure and other chronic illnesses which arise out of diet and lifestyle choices that are mismatched with our biology and our lives.
The chief question for us, as consumers and as nutritional professionals, is ‘in what context is this food being consumed’. The minutiae of an overall healthy diet can be debated eternally and yet there seems to be consensus that whole foods, not too processed, in a wide variety of colours, both cooked and raw, along with a smattering of good fats, good sources of protein and plenty of water will always be a good place to start. As is shown by the scientific research laid out above, we can micro-analyse our nutrients, and even our foods, until the cows come home (pun intended!) but the only way to make really sensible choices about what we eat is to look at our overall diet rather than the isolated compounds of specific foods. The diet we eat should be a place where nutrients balance and complement one another through the consumption of a wide variety of nutritionally diverse foods. Red meat can be very much a part of that broad, rounded, balanced diet.