Archeological and anthropological evidence indicate that humans and our prehuman ancestors have been eating meat for over 2 million years. The artifacts from our hunting and eating animals are beyond dispute, as is the isotope evidence showing that humans in the Upper Paleolithic ate as least as much meat as top level carnivores like canines ^[1]. This extensive period eating high levels of meat gave us ample time to adapt to meat as a food. In fact, our digestive system clearly indicates not just tolerance to meat eating, but dependence on it! Long before we had access to cooking or agriculture ^[2], we lost all but a small fraction of the ability to digest fibre ^[3]. In herbivorous primates, fibre is transformed into fat by bacteria in the colon and cecum. This fat is their primary source of energy. Without this large-scale ability to use fibre for fuel, and without extensive use of cooking and cultivating starchy food, energy from plant sources would not have been sufficient to meet our needs ^[4]. There is simply no other plausible way we could have supported those needs without using fat from large mammals. Moreover, we could not have grown the brains we did during that period without access to high levels of particular nutrients brains require to develop properly ^[5].

Comparing plants and animal foods as sources of essential nutrients, animal sources are typically superior in both quantity and bioavailability. Vitamin B12 cannot be obtained at all without either eating meat or using supplements derived from obscure sources. Without meat, other vitamins, essential fats, and amino acids need to be carefully accounted for and often rely on year-round access to plant varieties that have only recently become so accessible. As a lifestyle choice in the modern era, this can be achieved, but it would be implausible evolutionarily. When we further take into account the anti-nutrient content of plant foods, we can better understand the nutritional crises people are facing in countries with inadequate access to red meat. Studies by the World Health Organization have shown that the most detrimental worldwide deficiencies would be solved if there were less reliance on grains and legumes and more access to animal sourced nutrition ^[6]. The brain may be the most affected. Deficiencies in iron, zinc, retinol, and B vitamins caused by reliance on plant sources of protein and low meat intake are responsible for high rates of cognitive deficits, mental disturbances, and blindness in developing countries.

Most scientific literature arguing that red meat is dangerous is one of two kinds. The first kind is epidemiological. It makes associations between groups of people eating different amounts of red meat and health outcomes. Some of these studies, but not all of them (see e.g. ^[7]), find higher levels of meat intake are related to higher levels of disease intake. There are many reasons these studies do not make good evidence, all ultimately related to the problem of establishing causality. One problem is that the associations are weak, typically with hazard ratios well below 2.0, a standard of associational significance when arguing for causal relationships ^[8]. Another problem is that they are highly confounded; eating meat is associated with behaviours that undermine health which may be the true cause of the association. More generally, associations are simply not able to discriminate between different causal structures, and most follow up studies based on these studies fail to confirm the hypothesised causal relationship. In addition to these, there are some experiments demonstrating plausible mechanisms. This kind of study often involves giving an animal model high doses of particular compounds found in meat and demonstrating higher susceptibility to a disease. While these studies do reveal possible biochemical pathways, they are not representative of humans eating meat in regular quantities.

Given that we evolved eating red meat in large quantities, and that it is high in necessary nutrients, it seems unlikely that it would be dangerous compared to alternative food we might choose. It could instead be argued that not eating red meat is dangerous, because it risks nutrient deficiencies and unknown complications from deviating from the evolutionary norm.

Notes

1. Jaouen, K. et al. Exceptionally High Δ15N Values in Collagen Single Amino Acids Confirm Neandertals as High-Trophic Level Carnivores. Proceedings of the National Academy of Sciences 116, no. 11 (March 12, 2019): 4928–33.
2. Kennedy GE. From the ape’s dilemma to the weanling’s dilemma: early weaning and its evolutionary context. J Hum Evol. 2005 Feb;48(2):123-45.
3. Milton K. The critical role played by animal source foods in human (Homo) evolution. J Nutr. 2003 Nov;133(11 Suppl 2):3886S-3892S.
4. Aiello, LC. and Wheeler, P. The Expensive-Tissue Hypothesis: The Brain and the Digestive System in Human and Primate Evolution Current Anthropology, Vol. 36, No. 2 (Apr., 1995), pp. 199-221
5. Chazan, M. Toward a Long Prehistory of Fire. Current Anthropology 2017 58:S16, S351-S359
6. Allen, L. World Health Organization, and Food and Agriculture Organization of the United Nations. Guidelines on Food Fortification with Micronutrients. Geneva; Rome: World Health Organization ; Food and Agriculture Organization of the United Nations, 2006.
7. Dehghan, M. et al. Associations of Fats and Carbohydrate Intake with Cardiovascular Disease and Mortality in 18 Countries from Five Continents (PURE): A Prospective Cohort Study. The Lancet 390, no. 10107 (November 4, 2017): 2050–62.
8. Grimes, DA. and Kenneth FS. False Alarms and Pseudo-Epidemics: The Limitations of Observational Epidemiology. Obstetrics & Gynecology 120, no. 4 (October 2012): 920–27.

Amber O’Hearn, M.Sc., is a data scientist by profession with a background in math, computer science, linguistics, and psychology. She has been studying and experimenting with ketogenic diets since 1997, and more recently writing and speaking about her findings. Her review on the evolutionary appropriateness and benefit of weaning babies onto a meat-based, high fat, low carb diet, was included as testimony defending Tim Noakes in his recent trial. Amber has been eating a carnivorous diet for over 8 years. You can find more about her at her website ketotic.org.

Several key factors are thought to have been contributing to human brain growth, including hunting, cooking and increasing amounts of animal protein and fat. It is widely told, that hunting forced our ancestors to perform more complex tasks, including group hunting and e.g. anticipation and communication, and that this necessity resulted in an increase in our brain capacity. However, it is often forgotten that for evolution to take place, several factors need to be right at the same moment. In this case, several building blocks needed to be in sufficient amounts in our diet to make the growth of our brain possible.

Scientific evidence shows that the building blocks needed to build our complex brain are widely available in animal protein from aquatic resources such as molluscs, fish and shrimp, while they are nearly absent in meat from savanna dwelling counterparts, except for their organ meats. However, the latter are rarely consumed by the persons who need them most, i.e. pregnant women and small children, due to the typical roles of men and women in traditional hunter-gatherer populations and the absence of refrigerators until quite recently. Taken together, I contend that in popular science the role of hunting and consumption of mammals is grossly exaggerated, in part due to the male predominance in science in the past century.
Secondly, in contrast to the argument above in which I stated that red meat contains little, if anything at all, that cannot be deducted from other dietary sources, it can also be argued that red meat contains several components that are in fact unhealthy for us. Epidemiological evidence has long pointed to red meat as an important risk factor for cancer as well as cardiovascular disease.

Processing of red meat has long been known to be an important risk factor in this case, as sausages and salami for example contain many additives which are well known to be causing inflammation and hence both cancer and cardiovascular disease. However, these additives would not incriminate red meat per se, but rather the processing. Recently, several molecular lines of evidence have pointed to two structural components of red meat itself, which argue for it’s possible role in the genesis of diseases of civilization. First, Neu5Gc is a glycoprotein which plays a role in our immune system. Since sialic acid-binding immunoglobulin-type lecins (SIGLEC) are responsible for the recognition of ‘self’ and ‘non-self’ particles in our body the difference between humans and most other mammals in their respective Neu5Gc and Neu5Ac sialic acids, makes humans susceptible to a range of inflammatory related diseases, such as auto-immune diseases, cancer, cardiovascular disease as well as diabetes.

A second molecule that has recently (re)gained attention of trimethylamine N-oxide or TMAO. TMAO is an organic compound from the class of amine oxides and it is the degradation product of trimethylamine, which is in turn derived from choline. Several studies have shown that high intakes of dietary protein increase TMAO levels in blood, which are in turn associated with increased risk of cardiovascular events and mortality. On a molecular level, choline, carnitine, hence red meats, and lecithin have all been associated with increased levels of TMAO. Additionally, the gut microbiome plays an important role in the synthesis of TMAO, and vegan and vegetarian diets have been shown to decrease gut flora that readily convert precursors to TMAO.

Finally, we live on a planet where we have to think about other things than health from a dietary point of view. If the total mundane population would start eating the amounts of red meat presently consumed in Western countries that would mean the end of most other living species, except for our livestock’s. The ultimate consequences of this mass extinction are unknown, but will most likely have enormous impact on the possibility of human life (not to speak of the right we –do not- have to exterminate so many other species), and should (thus) be counteracted at all costs.

In summary, there is no reason to eat meat, except for e.g. palatability, while there is some evidence that meat may in fact be unhealthy, while there is ample evidence that our enormous livestock’s have major impact on the quality of both human and other life on our planet.

Remko Kuipers (1980) studied pharmacy and medicine at the University of Groningen. He is currently working as a cardiologist in training at the OLVG in Amsterdam. He is notably interested in preventive cardiology, a novel superspecialization in the Netherlands.

Kuipers also works as a writer. His first book, Het Oerdieet, was released in the beginning of 2014. His second book, Oergezond, in 2016.

Kuipers owns a small company which is specialized in Lifestyle interventions. He provides personal advice, training, workshops, seminars and presentations at national and international meetings. Contact can be made through LinkedIn or remkokuipers.com