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Meat consumption research – Part 6 Impact of meat and diet on human health

See Introduction/aim of research for the background to this work.

The Western “killer” diet

Modern food production systems ended millennia of food uncertainty for much of the world’s population. Unfortunately, this security has not reached the poorest billion of population who still struggle to feed themselves due to lack of income or resources. For the richer populations, effective food price deflation has stimulated over-consumption and considerable changes in diet. After years of increasing longevity, life expectancy is starting to retreat as more of the population succumbs to obesity, diabetes, cancer and heart disease.

The situation is so bad that diet-related diseases are now the largest cause of death in Western populations with over half the adult population being affected (Cordain et al. 2005). These diseases, which disproportionately affect populations of economically advanced countries include coronary heart disease, cancer and diabetes and have become known as “Western diseases”. Much of this disease can be prevented, which is shown by comparing disease rates between people that emigrate to the West and those that remain in their traditional environment.

When comparing the diets of populations suffering from these diseases and those that do not, some interesting features emerge. Firstly, the level of meat consumption does not seem to affect disease rates in traditional diets (Cordain et al. 2002). Even traditional communities living in Arctic areas with almost completely carnivorous diets are broadly free from the Western diseases.

This contrasts to studies done in Western countries that find links between increased consumption of red meat to increased disease rates of cancer for example. One of the primary recommendations from a 10 year study of the evidence by the World Cancer Research Fund and the American Institute for Cancer Research (WCRF/AICR 2007) is to limit the intake of red meat and processed meat.

The benefit of traditional diets

These findings show that when studying diets, it is necessary to consider the whole diet and that drawing conclusions on constituent parts can be problematic. It also shows that the evolutionary process behind the development of traditional diets has created healthy diets based on extremely diverse food constituents. Due to the evolutionary nature of the food choices in traditional diets, only choices that promoted survival tend to be passed on to later generations. An excellent example of how well such adaptation works and what can happen in its absence is seen in the history of maize consumption. Native populations in the Americas that ate maize as a staple food mixed lime from ash or shells into their cornmeal releasing the niacin that is usually unavailable in the grain (Levetin & McMahon 2003). They also tended to eat the maize with other foods such as beans, which ensured that they were eating a balance of the essential amino acids. When maize became popular to Europeans, the preparation methods of the native Americans were not copied and large numbers of people that came to rely almost exclusively on maize developed pelagra, a niacin deficiency disease which can be fatal.

The need to consider whole diets rather than constituents parts puts nutritional scientists in a difficult position. There are too many variables to analyse when attempting to study a sample’s current diet, previous diet and environmental factors in detail. Therefore, they have no choice but to study broader categorisations within diets and produce data that cannot explain all factors.

Confusion over official nutritional guidance

Unlike in countries with stronger traditional food traditions, in the US and similar cultures, official nutritional guidance has come to play a considerable role in people’s relationship with food. Consumers have ended up being confused by such advice as it appears to change over time. A closer look at the issue reveals a complex situation where guidance from official nutritional science is often affected by other political interests.  In her book Food Politics Marion Nestle (2002) highlights how advice in 1977 to “decrease consumption of meat” was changed to “choose meats… which reduce saturated fat intake” after intense pressure from the meat industry. Further interference resulted in this being changed to “[consume] relatively… less red meat” in 1979 and “choose lean meats” in the 1980s.

The situation is further confused by nutritional information disseminated or sponsored by food companies which may be mistaken for official guidance. Media reporting of guidance and theories are prone to exaggerate differences and sensationalise in order to make a more interesting story. As a result, consumers are often left worried and confused.

This confusion does little harm to the food industry as it undermines other, clearer dietary messages. It also creates opportunities for new products which cater for whatever nutritional idea is popular at the time like “low fat” or “low carb” products.

Suspects within the Western diet

When the whole evolutionary background of humans is taken into account along with the evidence of how little our physiology has changed recently, it becomes clear that staple agricultural foods are relatively novel introductions that have been eaten for a fraction of the time of our recent evolution. Agriculture has been around for 15,000 years at most and many of the worlds populations have taken it up much more recently. The nutritional profile of grains, agriculture’s staple, make them very different from the foods that we traditionally exploited. Technology to refine their already high concentrations of carbohydrates have exacerbated this situation. From this perspective, meat can seem completely benign, with its long historic consumption, often at high concentrations.

When we look at the modern Western diet and how it has developed in the last century we see novel foods taking over quite significant parts of the diet. Vegetable oils, which apart from olive oil are a relatively recent product of industrial processing, have become ubiquitous, used for margarines, frying and in the processing of many foods. Cheap sweeteners, originally cane sugar and more recently high fructose corn syrup (HFCS) have become a worryingly significant source of calories for much of the population. HFCS, invented in the 1970s and used widely to replace sugar from the mid 1980s raises particular questions regarding the long-term affects of high consumption of a novel food.

More concerns are raised by the recent dominance that soya bean derivatives have come to play in the food system. In her recent book Eat your heart out, Felicity Lawrence (2008) pulls together some of these concerns… Soya has been used in Asian societies for a long time but almost exclusively after complex processing such as fermentation. This type of processing is found to significantly reduce the levels of phyto-oestrogens that naturally occur in the beans. Furthermore, traditional varieties used in Asia have reduced levels of these compounds in general compared to the disease-resistant modern Western varieties. These phyto-oestrogens have spread throughout the Western processed food chain due to the benefits that soya products provide the food processing industry. Unfortunately, there is growing concern about the side-effects these compounds may cause due to their potential to disrupt human hormonal systems.

Although meat looked like a safe food when looking at the evolutionary diet, some of the radical changes in animal raising that domestication and especially modern industrial systems have introduced throw doubt on that safety. Most of the meat we ate in the past was from wild animals which tend to have little fat unless they are very large or live in cold climates. These wild animals obviously ate natural diets and lead active lives. Ever since animal husbandry took off we have been affecting some of these variables through breeding, dietary change and movement restriction. Modern livestock systems take these changes to an extreme.

The fattening of cows with grain for example, which accounts for most of the beef eaten in the US, forces a completely unnatural diet on the animals, causing physiological problems that have to be mitigated through the use of pharmaceuticals. The diet causes acidification of the cow’s digestive organ, the rumen, which has led to development of acid-tolerant and therefore more dangerous Escherichia coli bacteria (Pollan 2006).

The unnatural diet for cattle also changes the nutritional profile of the meat, raising overall fat levels and increasing the ratio of omega-6 to omega-3 fatty acids. The increased total intake ratio of omega-6 to omega-3 fatty acids in our diets is thought to be linked with various health problems (Pollan 2008). When factors such as the unnatural speed of growth on such a high-energy diet and the lack of exercise available to penned animals are taken into account, it is clear that beef meat has significantly changed from how it used to be. Grass-fed beef can still be found, even in the US and this provides a meat that is virtually unchanged from that produced a hundred years ago. It would even be similar to the meat that was hunted from wild prairie-grazing animals that hunter-gatherers would have exploited.

When it comes to the other two main meat-sources, chicken and pork. Most industrially-raised chicken is raised in sheds with very high population concentrations making exercise, natural behaviour and disease control difficult. The chickens have been bred for extreme efficiency of converting feed into meat in as short a time as possible. This selective breeding has been so extreme that many birds suffer serious health problems from the speed of their growth. Industrially raised pigs are again usually raised indoors in high concentrations and sometimes extreme confinement with little chance to practice natural behaviour. Although bred for fast growth, their health is not impacted to the same extent as with chickens.   Again there are alternatives available, free-ranging and naturally-fed chicken and pork can be found, if not at the same cost as the industrial versions.

It is reasonable to conclude that these modern changes to animal raising are implicated in the decline of our dietary health and may explain how meat-eating has shifted from being an aid to health to being a risk factor.

The spread of modern production systems has made the Western diet available to a greater proportion of the world’s population. This means that today’s developing countries can afford to eat meat at a much lower GDP than countries in the past (WCRF/AICR 2007). This helps to explain why the Western diseases are becoming more prevalent in countries like China, India and Brazil.

In Michael Pollan’s new book “In Defence of Food” (2008) he investigates the possible causes of the Western diseases. Afterwards he proposes some rules that would help avoid the diet that causes them. The first of these is “Don’t eat anything your great grandmother wouldn’t recognize as food” in order to avoid many of the novel additions to our diets that are implicated in ill-health and return to a diet based more on tradition than on industry, marketing and science.

With consideration of our greater evolutionary diet in the last couple of hundred thousands years, perhaps the best possible advice for a healthy diet would be to eat like our palaeolithic ancestors or modern hunter-gatherers. However, few of us would have access to the knowledge that would be essential to eat such a diet, nor would there be the environment to feed more than a fraction of humanity in that way. However, some nutritional scientists are now putting together research on evolutionary and traditional diets and the impact of more novel food introductions. This may lead to better ideas for improving Western dietary health.

Food pathogens

One final health issue that is often caused by livestock production and meat processing is that of food poisoning or food-borne illness – modern livestock production, with its concentration of vast numbers of genetically similar animals together in close confinement makes disease evolution and proliferation a major issue. Some of these diseases threaten human health on a gigantic scale. The avian influenza outbreak that caused panic in 2005 could have become a human epidemic with the right conditions. A similar disease outbreak in 1918 killed around 20 million people (Singer & Mason 2006).

Practices such as feeding unnatural diets to cows create more dangerous pathogens (Pollan 2006). Liberal use of antibiotics helps create antibiotic-resistance and threatens our ability to treat diseases. Due to the size of the industry and its operations, when mistakes are made the results impact large numbers of people. In the US, something like 200,000 people are thought to be affected by food-borne illness every day with 900 of those needing hospital treatment and 14 being killed (Schlosser 2002).

One of the most dangerous pathogens is a recently mutated form of Escherichia coli, type O157:H7, first identified in 1982. Its danger lies in its virulence, ingesting as few as 10 bacteria could prove fatal (Pollan 2006). Most of its spread is from undercooked, contaminated beef products, at slaughter meat can be contaminated with cow faeces that harbour the bacteria, around 40% of feedlot cattle are found to contain it. Even avoiding beef does not guarantee safety, in 2006 an outbreak was traced to Californian spinach which may have become contaminated by manure run-off from a cattle farm (San Francisco Chronicle 2007).


Cordain L, Eaton SB, Brand Miller J, Mann N and Hill K. 2002. The paradoxical nature of hunter-gatherer diets: meat-based, yet non-atherogenic. European Journal of Clinical Nutrition (2002) 56, Suppl 1, S42–S52

Cordain L, Eaton SB, Sebastian A, Mann N, Lindeberg S, Watkins BA, O’Keefe JH and Brand-Miller J. 2005. Origins and evolution of the Western diet: health implications for the 21st century. American Journal of Clinical Nutrition 2005;81:341–54.

Lawrence, Felicity. 2008. Eat Your Heart Out: Why the food business is bad for the planet and your health. Penguin Books.

Levetin, Estelle & McMahon, Karen. 2003. Plants and Society, 3rd Edition. McGraw-Hill Higher Education

Nestle, Marion. 2002. Food Politics: How the food industry influences nutrition and health. University of California Press.

Pollan, Michael. 2006. The Omnivore’s Dilemma. Penguin Press.

Pollan, Michael. 2008. In Defence of Food: The myth of nutrition and the pleasures of eating. Allen Lane.

San Francisco Chronicle. March 23rd 2007. San Benito County ranch source of tainted spinach. Available at http://www.sfgate.com Accessed: February 13th 2009

Schlosser, Eric. 2002. Fast Food Nation: What the all American meal is doing to the world. Penguin Books.

Singer, Peter and Mason, Jim. 2006. The way we eat: Why our food choices matter. Rodale.

World Cancer Research Fund / American Institute for Cancer Research (WCRF/AICR). 2007. Food, Nutrition, Physical Activity, and the Prevention of Cancer: a Global Perspective. Washington DC: AICR

3 Responses

  1. This is an awesome paper on meat consumption.

    I have yet to read it all, but what an exciting find! Best,


  2. I read the whole thing Henry! Very well written clarification of what is wrong and why…. thank you x

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