Do humans need meat for good health?
by Dr Shireen Kassam and Michael Metoudi, RD
The simple answer to this question is a definite NO! and these are the reasons why.
What our ancestors have taught us?
Humans are opportunistic omnivores. This means we can eat a range of different foods from plants and animals and therefore have a choice on how we can obtain essential nutrients from our food. Our ancestors were foragers, mainly gatherers, and occasional hunters. Recent data published in the journal Science now suggests our ancient ancestors ate a predominantly plant-rich diet and were well adapted to eating starchy vegetables and grains, achieving around 100g of fibre a day, with only occasional meat, when available. We know this through archaeological evidence using modern techniques that analyse both chemical and physical compositions of bones and teeth, which have now been used to evaluate our ancestors’ dietary patterns. These are significant findings, as they go against the modern theory that meat is responsible for the large increase in brain size in modern humans. The meat, when consumed, would have been from wild animals that differ considerably in nutritional composition, being much lower in saturated fat and higher in omega-3 fatty acids, compared to the meat from factory farmed animals being consumed today.
From the dawn of nutrition science, we have learnt that the only foods associated with good health and a reduced risk of chronic diseases, are those derived from plants, i.e. fruits, vegetables, whole grains, legumes such as beans, nuts and seeds. Dairy only became a part of our diet after the domestication of animals around 10,000 years ago. It is only in some communities, mainly Europeans, who have acquired the ability to digest lactose beyond weaning due to a genetic mutation in the lactase enzyme gene. This was only due to selective pressure as a result of extreme famine or food scarcity during those periods for human survival. Most of the world remains lactose intolerant, the natural state.
Very few traditional hunter gatherer tribes still exist, mainly due to dietary acculturation (i.e assimilation towards modern and western-style diets). One such tribe that remains are the Tsimane people in Bolivia. They have the lowest rates of heart disease of any community around the world. Their diet is predominantly composed of high fibre whole plant foods. In contrast, when we look at tribes that often eat a predominantly meat-centred diet such as the Maasai tribe, located in southern Kenya and northern Tanzania, they supposedly are reported to have low rates of heart disease and are often used as evidence to promote meat-based diets. However we see prevalent rates of hypertension and hyperlipidemia, with atherosclerotic plaques existing among many of these tribes. Whilst their overall heart disease rates may appear to be lower, this is likely due to several important confounding factors, such as favorable genetic adaptations to cholesterol metabolism, very high physical activity levels and lower overall life expectancy relative to the countries’ average, preventing many from reaching the age at which heart disease typically manifests.
A surge of interest has also occurred in recent years on the historical paleolithic diet (or paleo), a ‘modern eating plan’ that mimics the presumed diet of humans during the paleolithic era. It is often touted as the healthiest dietary pattern due to its focus on unprocessed foods such as fruits and vegetables and high fibre, but with higher intakes of meat, fat and low intake of starch carbohydrate foods. While there is some evidence of the diet improving blood lipids linked to heart disease risk, this may be due to the very high fibre content of the diet and recent evidence shows no additional benefit compared to other healthy dietary patterns on improving other important metabolic health outcomes, such as diabetes risk.
Isn’t animal protein better quality than plant protein?
We appear to be obsessed with protein, an obsession largely fuelled it seems by the meat industry. Protein is indeed an essential macronutrient, but it only becomes an issue in situations where food is in short supply, such as in times of famine, when people are not able to meet their calorie requirements. This is often the case in certain regions of Sub-saharan Africa where conditions such as kwashiorkor and marasmus exist, characterised by protein insufficiency and are often endemic to the regions, due to severe states of malnutrition.
For those of us who can easily meet our calorie needs, protein requirements are easily met and usually exceeded by eating a diet composed of a range of healthy plant foods. Legumes such as beans, chickpeas, lentils and soya foods such as tofu, tempeh and edamame, nuts and seeds are particularly concentrated sources of plant protein but vegetables and whole grains in higher proportions often contain adequate amounts too.
People often worry that plant proteins don’t contain all the required amino acids and are therefore ‘incomplete’ proteins. The belief stems from outdated research from the 1970s, popularized by Frances Moore Lappé in her book Diet for a Small Planet. This has been debunked several times, despite it still being believed, even from many health professionals. All plants contain all 9 of the essential amino acids that the body requires, just in different proportions to animal sources of protein. You therefore don’t need to worry about combining certain foods to make up the right amount of amino acids, you only need to make sure you are eating a variety of plant protein foods daily or over a few days. Concerns also exist over the digestibility and absorption of plant protein and therefore their quality being inferior compared to meat. This is largely due to two methods that score protein digestibility such as the PDCAAS and the DIAAS scoring systems. There are several limitations to these methods, particularly when it comes to plant proteins. Most notably the fact it was designed for animals in mind and not humans!.
It turns out that plant protein is better for health than animal protein. We now have many studies globally confirming that swapping out animal protein for plant protein for our health. The most recent systematic review and meta-analysis showed a significant reduction in the risk of cardiovascular, type 2 diabetes and all cause mortality (i.e. the chances of dying) when swapping out certain animal foods for plant-based alternatives. For example, swapping out meat with nuts reduces the risk of cardiovascular disease by 28% and 22% for Type 2 diabetes. The same study showed substituting eggs with either legumes or nuts was associated with an 18% and 10% reduced risk of dying by any cause.
Why might plant protein be better for health?
The reason plant sources of protein are healthier is because the protein comes packaged with healthy and protective nutrients. These nutrients include fibre, unsaturated fatty acids, vitamins, minerals, antioxidants and anti-inflammatory compounds. In contrast, animal protein comes packaged with nutrients we know are harmful to health including saturated fat, implicated in the development of cardiovascular disease. Haem iron, predominantly found in red meat, is known to create inflammation and also increases the risk of cardiovascular disease and type 2 diabetes. Higher levels of advanced glycation end products, compounds that are produced in meat during cooking are implicated in a number of chronic diseases, including dementia and certain cancers. Animal protein is also completely devoid of fibre and other beneficial anti-inflammatory compounds which appears to have a negative impact on beneficial gut bacteria and an increase in harmful gut bacteria, depending on the source of the protein. Certain gut bacteria utilise and convert meat into a harmful metabolite known as TMAO which is known to accelerate the onset of cardiovascular disease. A more recent pro-inflammatory molecule known as Neu5Gc, found within red meat, has also been identified and appears to have the potential in driving certain cancers.
The protein from meat itself in isolation also appears problematic. Because of the unique composition, animal proteins are high in branched chain amino acids (BCAAs) that have links to several inflammatory diseases. Dietary BCAAs from meat were recently shown to more than double the risk of developing rheumatoid arthritis These amino acids have also been implicated in cancer development, and increases the risk of type 2 diabetes and kidney disease. The Academy of Nutrition and Dietetics, the world’s leading organisation of nutrition and dietetics, have recently updated their guidance on vegan and vegetarian diets (devoid of meat) in a position paper and state that “vegan dietary patterns can be nutritionally adequate and can offer long-term health benefits”, significantly reducing the risk of heart disease.
Don’t you need animal protein to gain muscle?
This is a myth that has been debunked by several recent scientific articles. For example, a meta-analysis of randomised control trials showed that protein from soya is just as effective at supporting muscle strength, lean muscle mass and growth as animal protein. Similarly, another recent meta-analysis also showed no difference in muscle mass, strength and overall performance, particularly within older adults too, when comparing plant protein from soya vs. animal protein. It is important to note that resistance exercise is also an important factor in maintaining muscle mass, particularly in the older adults and works synergistically with adequate intakes of protein.
Wider implications of eating meat
Our obsession with animal protein is also harming the planet. Animal agriculture is a leading driver of greenhouse gas emissions, biodiversity loss, species extinction, ocean and land pollution and more. Raising animals for food is fuelling the rise of antibiotic resistant infections in humans and poses a major risk for the generation of new infections with pandemic potential. When all these factors are considered, in addition to the negative impact of animal protein on human health, the evidence supporting the removal of animals from the plate becomes irrefutable.
Conclusion
It is clear that meat is not necessary in the human diet. Replacing animal protein with plant protein can significantly improve personal and planetary health and is of course kinder to the non-human animals with which we share this earth. In this era of increasingly conflicting information surrounding meat consumption and health, it is important to consider how we can evaluate non-bias research on this topic, which often is biased depending on who is funding the research studies. This is usually through conflicts of interest from special interest groups.
Read more about meeting protein requirements on a plant-based diet in our factsheet.