Should Humanists be Vegans?

Can we feed a future population of 10 billion people a healthy diet within planetary boundaries? The EAT-Lancet Commission recently brought together more than 30 world-leading scientists from across the globe to address this question and reach a scientific consensus that defines a healthy and sustainable diet. Their landmark report (Food, Planet, Health) integrates, with quantification of universal healthy diets, global targets for sustainable food system (1). The conclusions in this report suggest that all of us should be drastically reducing our meat and dairy consumption if we care for the health of our fellow humans and the long-term health of our planet.

The Food and Agriculture Organization defines sustainable diets as those that are protective and respectful of biodiversity and ecosystems, nutritionally adequate, safe, healthy, culturally acceptable, economically affordable, while optimising natural and human resources (2). Calls for dietary guidelines to include sustainability began more than thirty years ago (3) and a number of international dietary guidelines panels have considered the sustainability of the food system when producing recommendations (4). Nonetheless there is a wide disparity in the carbon emissions intensity of the healthy diets recommended in different countries, ranging from 687kg CO2 equivalents per capita per year in India to 1579kg in the USA (5).

Today global climate change is recognised as an urgent problem, along with other pressing environmental issues including loss of biodiversity, land degradation, fresh water shortages, and water pollution (6). The latest Intergovernmental Panel on Climate Change special report assessed energy, land and ecosystems, infrastructure and industry to see how they would need to be transformed to limit global warming to 1.5°C. It concluded that among the actions needed is changing food systems and promoting diet changes away from land-intensive animal products (7).

Global agriculture and food production release more than 25% of all greenhouse gases (GHG) (8). Emissions vary widely between foods; ruminant meats such as beef and lamb can have emissions per gram of protein 250 times that of legumes, while eggs, seafood, poultry and pork have much lower emissions than ruminant meat. How a given food is produced also affects emissions. When sustainably grazed on lands unsuitable for cropping, dairy and red meat production can increase food security, dietary quality and provide environmental benefits via nutrient cycling (9). Nonetheless, while producers have some limited ability to reduce the environmental impacts of food production, dietary change will remain the most effective mechanism to deliver environmental benefits (10). Using global life-cycle analysis of emission data, it has been calculated that a move to a Mediterranean, pescatarian or vegetarian diet could reduce GHG emissions from food production by 30-55% (8).

The literature on sustainable diets has grown substantially in the last decade (11-13). A recent study examined 66 different dietary studies that enabled comparison of their nutritional quality and carbon footprints (14). The authors found that the Mediterranean diet and the Atlantic dietary pattern (common in northern Portugal and Galicia), as well as those in India and Peru had much lower carbon footprint scores than the diets of north or western Europe and concluded that a shift to a diet rich in vegetables and lower in animal protein would be healthier and more environmentally friendly. Other studies have also concluded that reductions in meat consumption would lead to reductions in GHG emissions since those of meat and dairy consumers are about twice those of vegans (15-18).

In the current Australian dietary guidelines, published in 2013, the topic of environmental sustainability is only briefly mentioned in a five page appendix, and its key messages focus on issues of food waste, healthy food choices and buying locally grown food, rather than any recommendations to change food patterns substantially (19). There have been attempts to describe what a healthy and sustainable diet could look like in Australia (20) but in general the topic does not get the attention it deserves at the level of government policy making (21) and intersectoral action has been hampered by disparate definitions, a perceived lack of robust evidence, and divergent views about the role of government in environmental policy and food regulation (22).

It seems clear that moving to a diet based on more whole and plant-based foods is going to be one of the most important dietary strategies at a global level both for the planet and for human health. However, the dietary choices that an individual makes are influenced by culture, price, availability, taste and convenience, as well as nutritional knowledge. If we are going to encourage the move to a food system that is more environmentally sustainable, there will need to be programs to educate consumers on how to do this and the development of food policy, dietary guidelines and labelling regulations that articulate the changes needed. There is already a high level of community concern in Australia about the environmental impact of the food supply (23). We may discover that many individuals find concerns about environmental impact more motivating than concerns about health when considering whether to make a dietary change.

Peter Williams, BSc(Hons), DipNutrDiet, MHP, PhD, FDAA
Honorary Professorial Fellow, School of Medicine, University of Wollongong


1. Willett W, Rocktröm J, Loken B et al. Food in the Anthropocene: the EAT-Lancet Commission on healthy diets from sustainable food systems. The Lancet. 2019;online:

2. Food and Agriculture Organization of the United Nations. International Scientific Symposium on Biodiversity and Sustainable Diets United Against Hunger. Rome: FAO; 2010 [Available from: Accessed 29 January 2019.

3. Gussow J. Dietary guidelines for sustainability. J Nutr Educ. 1986;18:1-5.

4. Gonzalvez Fischer C, Garnett T. Plates, pyramids and planets. Developments in national healthy and sustainable dietary guidelines: a state of play assessment. Rome: Food and Agriculture Organization of the UN and the Food Climate Research Network, 2016.

5. Ritchie H, Reay D, Higgins P. The impact of dietary guidelines on climate change. Global Environ Change. 2018;49:46-55.

6. Cribb J. The Coming Famine. The gobal food crisis and what we can do about it. Collingwood: CSIRO Publishing, 2010.

7. Masson-Delmotte V, Zhai P, Pörtner H et al. Global warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty. Geneva: World Meterological Organization, 2018.

8. Tillman D, Clark M. Global diets link environmental sustainability and human health. Nature. 2014;515:518-22.

9. Eisler MC, Lee MR, Tarlton JF et al. Agriculture: steps to sustainable livestock. Nature. 2014;507(7490):32-4.

10. Poore J, Nemecek T. Reducing food's environmental impacts through producers and consumers. Science. 2018;360:987-92.

11. Nelson ME, Hamm MW, Hu FB et al. Alignment of healthy dietary patterns and environmental sustainability: a systematic review. Adv Nutr. 2016;7(6):1005-25.

12. Hallström E, Carlsson-Kanyama A, Börjesson P. Environmental impact of dietary change: a systematic review. J Clean Prod. 2015;91:1-11.

13. Aleksandrowicz L, Green R, Joy E et al. The impacts of dietary change on greenhouse gas emissions, land use, water use, and health: a systematic review. PLoS One. 2016;11(11):e0165797.

14. Gonzalez-Garcia S, Esteve-Llorens X, Moreira M et al. Carbon footprint and nutritional quality of human dietary choices. Sci Total Environ. 2018;644:77-94.

15. Scarborough P, Appleby PN, Mizdrak A et al. Dietary greenhouse gas emissions of meat-eaters, fish-eaters, vegetarians and vegans in the UK. Clim Change. 2014;125:179-92.

16. Springmann M, Wiebe K, Masson-D'Croz D et al. Health and nutritional aspects of sustainable diet strategies and their association with environmental impacts: a global modelling analysis with country-level detail. Lancet Planet Health. 2018;2(10):e451-e61.

17. Perignon M, Vieux F, Soler L et al. Improving food sustainability through evolution of food choices: review of epidemiological studies on the environmental impact of diets. Nutr Rev. 2017;75(1):2-17.

18. van de Kamp M, van Dooren C, Hollander A et al. Healty diets with reduced environmental impact? The greenhouse gas emissions of various diets adhering to the Dutch food based dietary guidelines. Food Res Int. 2018;104:14-24.

19. National Health and Medical Research Council. Food, nutrition and environmental sustainability.  Eat for Health Australian Dietary Guidelines. Canberra: NHMRC; 2013. p. 130-4.

20. Friel S, Barosh LJ, Lawrence M. Towards healthy and sustainable food consumption: an Australian case study. Pub Health Nutr. 2013;17(5):1156-66.

21. Trevena H, Kaldor JC, Downs SM. 'Sustainability does not quite get the attention it deserves': synergies and tensions in the sustainability frames of Australian food policy actors. Pub Health Nutr. 2014;18(13):2323-32.

22. James S, Friel S, Lawrence M et al. Inter-sectoral action to support healthy and environmentally sustainable food behaviours: a study of sectoral knowledge, governance and implementation opportunities. Sustain Sci. 2018;13(2):465-77.

23. Harray A, Meng X, Kerr D et al. Healthy and sustainable diets: community concerns about the effect of food environments and support for government regulating sustainable food supplies in Western Australia. Appetite. 2018;125:252-32.