EXPERT REACTION: Downsides to high meat consumption

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A review has examined the consequences of a high meat diet and says future changes in global meat consumption will have major effects on both the environment and our own health. Though meat can be an important source of nutrients, the researchers say high consumption can increase the risk of some types of diseases, particularly colorectal cancer. Coupled with environmental impacts, including greenhouse gas emissions, they suggest we need to know more about how best to convince people to change their diets and cut back on meat.

Journal/conference: Science

Link to research (DOI): 10.1126/science.aam5324

Organisation/s: University of Oxford, UK

Funder: Wellcome Trust.

Media Release

From: AAAS

What Does Science Tell Us About the Effects of High Meat Consumption?

In this Review, part of the ongoing Tomorrow’s Earth series at Science, Charles Godfray et al. highlight the impacts of meat consumption on human health and the environment. Although meat can be an important source of nutrients, high meat consumption may increase the risk of some types of disease. The authors note that, although teasing apart confounding factors such as smoking and obesity can be tricky, large-scale studies of Western countries have linked high-red and -processed meat intake with greater mortality rates and some diseases, and colorectal cancer in particular. In terms of environmental impacts, meat production results in more greenhouse gas (GHG) emissions per unit of energy compared with plant-based foods. The long-term implications of livestock-associated GHGs on climate change depend on the type of gas and at what rate it is being emitted; since some accumulate and decay differently than others, methane and nitrous oxide will contribute the most to climate change over the long-term. After discussing the impacts of water allocation and rainforest conversion for agricultural purposes, Godfray et al. highlight possible ways to change peoples’ meat consumption behavior, a tricky feat, but with some options to date showing efficacy. One example they cite is certification programs run by the private sector or nongovernmental organizations, which provide trusted evidence about welfare or environmental standards. As well, they note that fiscal interventions show some promise, citing a case in Denmark where meat was taxed higher.


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Expert Reaction

These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.

Bradley Ridoutt is a Principal Research Scientist for CSIRO Agriculture and Food

Godfray et al. argue the need for diets to shift away from meat consumption for the sake of human health and the environment. However, their analysis misses the mark.

Overlooked is the importance of reducing the intake of discretionary foods to improve diet quality and reduce environmental impacts. Discretionary foods, which are energy rich and nutrient poor, come in many different forms. They include sugar-sweetened beverages, beer and wine, dairy desserts, processed meats, biscuits, cakes and pastries, fried hot potato chips, salted snacks, jam, honey, confectionery, and many others.

For individuals with low to moderate levels of physical activity, there is little room for discretionary foods in a nutritious and energy balanced diet. As such, the National Health and Medical Research Council in Australia recommends they be eaten only occasionally and in small amounts (1).

However, in practice, these foods make up a considerable proportion of food consumption in developed and developing countries alike (2). In Australia, teenagers from 14 to 18 years obtained more than 40 per cent of dietary energy from these sources (3). Discretionary foods also greatly inflate environmental impacts from the food system.

In Australia, more than 9,000 individual adult daily diets were assessed for diet quality and greenhouse gas emissions (GHGE) (4). When higher-quality and lower-GHGE diets were compared to lower-quality and higher-GHGE diets, the differences in GHGE were 44 per cent for males and 46 per cent  for females, mainly due to differences in discretionary food consumption. At the population level, eating according to dietary guidelines and reducing food waste are the safest and least controversial recommendations to make diets healthier and more sustainable.

Animal-based foods can be an important and high-quality source of nutrients. The Australian Dietary Guidelines suggest that some children and young women may benefit from the additional nutrients associated with an increase in lean red meat consumption (1).

In addition, the environmental impacts of animal-based foods are not necessarily higher than plant-based foods (5). A comprehensive study of water footprints in Australia has shown that the agricultural products with highest water footprint were rice, nuts, cotton, summer legumes, stone fruit, summer oilseeds, grapes and citrus (6).

1National Health and Medical Research Council and Department of Health and Ageing, “Australian Dietary Guidelines” (2013;
2B. M. Popkin, Obes. Rev. 15 (Suppl. 1), 60–67 (2014).
3Australian Bureau of Statistics, “4364.0.55.007 - Australian Health Survey: Nutrition First Results - Foods and Nutrients, 2011-12” (Canberra, 2014).
4B. Ridoutt, G. Hendrie, D. Baird, M. Hadjikakou, M. Noakes, paper presented at the 10th International Conference on Life Cycle Assessment in the Agri-Food Sector, Dublin, Ireland, 19-21 October 2016.
5B. G. Ridoutt, G. A. Hendrie, M. Noakes, Adv. Nutr. 8:933–46 (2017); doi:
6B. G. Ridoutt, M. Hadjikakou, M. Nolan, B. A. Bryan, Environ. Sci. Technol. 52(12):6761–6770 (2018); DOI: 10.1021/acs.est.8b00416


Last updated: 20 Jul 2018 1:48pm
Declared conflicts of interest:
Bradley Ridoutt has undertaken food systems research related to environmental issues for a variety of private sector organisations and Australian government agencies. This includes Meat and Livestock Australia.
Professor Ralph Sims, Professor of Sustainable Energy, Massey University.

The analysis in the recent Science paper on meat consumption and the environmental and health issues involved is a good contribution to the current debate. Air New Zealand serving 'meatless' hamburgers has given it higher public attention but is just one example of growing trends. Another example is the recent contract for Israel to supply China with $US 300 million worth of synthetic protein products.

The global food supply system that has successfully fed the world’s growing demand for food protein is unsustainable in the long term. It consumes around 70% of freshwater withdrawals, uses around one-third of all end-use energy, has caused much loss of biodiversity as a result of land-use change and agri-chemicals, and produces almost one-quarter of greenhouse gases (GHG). Moves towards a more circular economy for food supply will grow rapidly.

As explained in this Science paper, meat consumption is the reason for a major share of these environmental impacts. As an example, for climate change, sheep and beef production result in greenhouse gas emissions of around 30-60 kg CO2-equivalent per kg of meat product (less for grass-fed animals than if kept in feedlots); seafood from fisheries is around 10 kg CO2-eq / kg product or less for aqua-cultural production; pork and poultry are lower at around 5 kg CO2-eq / kg product (mainly as they are mono-gastric animals, not ruminants, so do not produce methane during their food digestion process); and vegetable protein crops and 'synthetic' meat produced in laboratories can be as low as 2-3 kg CO2-eq /kg product.

The health risks from red meat consumption and impacts from the continuing use of antibiotics, are identified in the Science paper, but the additional  issue of animal welfare is only briefly mentioned, even though it is a major reason why some people choose to become vegetarians.

New Zealand sheep, deer and beef farmers, should pay close attention to changing global food consumption trends – as should the dairy farming sector. There will probably be continuing global demand for meat and milk proteins and there are areas of pasture land in New Zealand unsuitable for growing crops or even for forestry. So grazing animals there could be the best land use option. In addition, there are communities and cultures in many countries where meat is the main protein source – such as for the Masai in Kenya. However, there is a growing debate that demand per capita for animal protein provided by commodity products may decline in future.

Given the global food sector will have to produce around 70% more food by 2050 to meet growing demands (or possibly less if we can reduce the one third of food we currently fail to consume globally as a result of either losses after harvest or wastes after purchase); that land degradation and soil loss is increasing; and that the goals of the Paris Climate Agreement cannot be met unless the food sector plays a major role; increasing productivity per hectare may provide a partial solution in the short term but in the longer term we will have to make the transition to a more sustainable food supply system – and reducing meat consumption will have to play a part.  

Last updated: 19 Jul 2018 2:45pm
Declared conflicts of interest:
None declared.

Fiona Greig, Head of Nutrition, Beef + Lamb New Zealand Inc

The Godfray et al. paper acknowledges red meat provides a good source of nutrients, and diets low in meat may have negative health impacts when meat substitutes are not available.

"In New Zealand, this reinforces beef and lamb provide an efficient and sustainable source of essential nutrients to the diet, which can address nutrient intake needs and nutrient deficiencies including zinc, iron and vitamin B12.

"The body of evidence supports a moderate amount of lean red meat within a healthy diet, reinforced by the World Cancer Research Fund Report, which outlines overall dietary and exercise patterns are more important than individual foods. This underpins the New Zealand Ministry of Health’s eating and activity guidelines that includes 500g cooked red meat per week. 

"The theme of dietary patterns opposed to single foods, and an emphasis of dietary patterns that comprise mainly whole, less processed foods through our dietary guidelines, is echoed in a review of the evidence looking at dietary strategies to reduce environmental impact by Ridoutt and colleagues. They highlight assessing environmental performance of diets is complex due to the wide range of foods we eat, the diversity of agricultural systems and local environmental systems. The review highlights that in general, recommended diets, i.e. those in dietary guidelines, have a lower environmental impact than what is typically eaten, largely due to an overconsumption of food energy.

Last updated: 19 Jul 2018 2:02pm
Declared conflicts of interest:
Beef + Lamb NZ Inc is is responsible for the promotion of beef and lamb within New Zealand.

Garrett Lentz, PhD Candidate, University of Otago,

"The consumption of meat, at least when viewed from the global perspective, is one of the most environmentally damaging day-to-day behaviours that humans perform. This is due to the vast range and severity of impacts tied to the raising of animals for food, including land and water degradation; habitat and biodiversity loss; and contribution to pollution, ocean dead zones, and climate change. No matter the driver for change, whether it be for environmental sustainability; improved public health; or animal welfare; reduced meat consumption would result in a more efficient food system that could feed more people with fewer resources, thereby minimising at least some of the associated environmental impacts that are being seen today.

"Based upon findings from our research, it seems that people are unaware of the range and severity of meat’s environmental impacts — at least in comparison to other food behaviours — and that environmental sustainability, as a motivation for reducing meat consumption, is a low priority for the majority of consumers (at least in comparison with other motivations such as monetary and health considerations). In addition, it seems that attitudes and feelings of attachment towards meat are strongly correlated with willingness and intentions to reduce meat in the diet, as well as agreement with potential policy measures that could be implemented to promote reduced meat diets across larger society. Based upon these results, we believe that the next step is to investigate how motivations, attitudes, meat attachment, and agreement with policy measures might be shifted among consumers in order to promote reduced-meat diets for environmental sustainability benefits.

Last updated: 19 Jul 2018 2:01pm
Declared conflicts of interest:
None declared.

Professor Dave Frame, School of Geography, Environment and Earth Sciences, Victoria University of Wellington

Among other things, the paper reminds us that the effects of agricultural methane on the climate system are temporary, while those of carbon dioxide are far more permanent. The paper shows that agriculture sector is both crucial, and a sector that faces significant challenges in coming decades; challenges that climate change will usually amplify through disruptive impacts like droughts, extreme weather, and changes in the water cycle.

Last updated: 19 Jul 2018 2:01pm
Declared conflicts of interest:
None declared.

Dr Mike Joy, Senior Researcher, School of Government, Victoria University of Wellington

This paper follows on from a multitude of recent papers and reports highlighting the impacts of meat production on aquatic ecosystems, human health, antibiotic use atmosphere and much more. There is an interesting section on choices around changing diets, what drives changes and relationships with meat consumption and income, temporally and spatially.

"The section on economic assessment using the value of animal agriculture for different countries notably only includes gross income and ignores the much more important net income and the cost of externalities. The most glaring omission though, was the role of fossil energy in agriculture, not just on-farm but transport and processing and especially the massive input of fossil fuel energy in artificial fertilisers.

"The huge population growth enabled by the so-called ‘green revolution’ was almost completely driven by fossil fuel-derived nitrogen fertilisers. Now the vast majority of humans on the planet are dependant on fossil fuel-derived fertilisers and meat production is a very inefficient way to transfer this fossil energy to humans. Thus, the omission of fossil energy is crucial because, notwithstanding the other issues in the paper, feeding 9 billion people with the meat-based diets anything like today will be impossible given fossil fuel declines (details here).

Last updated: 19 Jul 2018 1:41pm
Declared conflicts of interest:
None declared.

Professor Robert McLachlan, Centre for Sustainable Futures & Professor in Applied Mathematics at Massey University

This is a thorough review by a multidisciplinary team spanning climate, environment, agriculture, health, behaviour, and ethics. It’s a model for how to approach such large-scale, complex, diverse issues. 

"On the health side, the main conclusion is the increased risk of bowel cancer from eating processed meat (and probably also red meat) — this was widely publicised in New Zealand last year. It’s highly relevant as bowel cancer causes about 4% of all deaths in New Zealand, high by world standards. 

"On the environment side, it is striking that the main issues worldwide — nitrogen and phosphorus runoff, water use, water quality, and greenhouse gas emissions — are the same as those we are grappling with in New Zealand. Demand for meat is expected to double by mid-century, so pressure for meat production to become sustainable, and for a carbon charge on its greenhouse gas emissions, is likely to increase.

"Meat and dairy are the main source of agricultural greenhouse gases. Globally, both short- and long-lived gases contribute, but in New Zealand’s pastoral system, methane is the main factor. The review concludes that 'meat production really matters in calculations of global warming but that distinguishing the effects of the different types of GHGs is very important for policy-makers'. So, the present debate in New Zealand has global significance.

"Unfortunately, the review also concludes that the tools available to influence meat consumption are limited and of uncertain impact, although this may be because, as in New Zealand, 'The existence of major vested interests and centres of power makes the political economy of diet change highly challenging'. But change is possible. In New Zealand, the consumption of red meat has fallen by 58% in just 10 years, and is now close to the average for rich nations, and close to recommended health limits on a population basis.

Last updated: 19 Jul 2018 12:19pm
Declared conflicts of interest:
No conflict of interest.
Associate Professor Taciano Milfont from the School of Psychology at Victoria University of Wellington

This Science article provides a state-of-the-art review of evidence regarding the increase in meat consumption worldwide as well as the impact of meat consumption on health and the environment. The article makes it clear that quantifying the effects of meat consumption on population health and the environment is not an easy task, but the available evidence indicates that global meat consumption has major negative effects on human health and the environment, and this might not be sustainable in years to come.

"Notably, the article focuses on interventions that might change individuals’ consumption preferences to favour a meat-free diet; however, this approach puts the responsibility on citizens while takes away the responsibility and mandate of governments to guarantee the wellbeing of citizens and their natural environment. Behaviour change interventions should be coupled with governments interventions on meat production, supply, and distribution.

"To contribute with knowledge about meat consumption in New Zealand, we are measuring dietary preference as part of the New Zealand Attitudes and Values Study. This will allow us to measure societal norms regarding meat consumption, change in meat consumption of New Zealanders over time, whether over-time increase/decrease in meat consumption is linked to their wealth (i.e., Bennett’s law), as well as effects of meat consumption on their health and wellbeing. 

Last updated: 19 Jul 2018 12:18pm
Declared conflicts of interest:
No conflict of interest.
Dr Cristina Cleghorn, Senior Research Fellow at the University of Otago

The consumption of processed meat is associated with a higher risk of colorectal cancer and processed and red meat may also increase people’s risk of cardiovascular disease and type 2 diabetes. Reducing consumption of processed and red meat could reduce the substantial health loss and costs to the New Zealand health system these diseases currently cause. This new review reports that transitioning from high meat to more plant-based diets might reduce global mortality rates by 6 to 10%. 

"It is possible for people to meet their nutritional needs without consuming meat and substantial reductions in meat intake would have a net positive impact on health. The World Cancer Research Fund recommends that people who eat red meat should consume less than 500g a week while the Global Burden of Disease project suggests people eat no more than 100g a week.

"New Zealand is economically invested in the production of meat which may be slowing the progress we could be making towards reducing average meat consumption. There is an opportunity for New Zealand to contribute to the production of new plant-based meat alternatives and start the shift away from animal-based agriculture.

"In order to generate health and climate co-benefits New Zealand could consider introducing an agricultural greenhouse gas tax, health and sustainability warning labels on meats and promotional campaigns to decrease meat consumption.

Last updated: 19 Jul 2018 12:12pm
Declared conflicts of interest:
No conflict of interest.

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