What, and indeed, how we eat can have a huge impact on not just our own health and wellbeing, but also the health of the planet and ensuring sustainable food supplies for future generations. When we bear in mind that agriculture is responsible for around 25% of all greenhouse gas (GHG) emissions and 80% of deforestation, occupies about 40% of the earth’s surface and uses 70% of the whole planet’s freshwater resources we can really appreciate that the foods we eat directly affect the planet’s future in a big way.1 The production of our food is also one of the largest drivers of biodiversity loss, species extinction and the degradation of natural resources, both on land and in marine systems which are heavily overburdened, with 60% of the world’s fish stocks fully fished, and 30% overfished.2
Our food system and consumption practices have, since prehistoric times, shaped and transformed our world and societies. Undeniable advances in agricultural practice and systems of storage and distribution have enabled population growth and improved the diets for many but these advances have also come at a cost, particularly to the environment. The global burden of morbidity from diet-related chronic diseases such as cardiovascular disease and type 2 diabetes is increasing, driven by both poor diet quality and an overconsumption of calories, and at the same time the world’s food production system is draining the planet’s resources, jeopardizing the environment and future food security. Personal, population and planetary health are closely intertwined through the food we eat, and all are vulnerable to threat unless we take action.9
The current steady shift of more of the planet towards a traditional western diet: typically low in fruits, vegetables, nuts, and wholegrains and high in red and processed meats, refined sugars, fats and oils, is responsible for many of the global health burdens. The incidence of overweight and obesity is also on the rise, with an estimated 1.9 billion adults being overweight, of which 600 million are obese, and childhood overweight is also becoming a global concern. This overconsumption and obesity, aside from its obvious health dangers also translates directly and indirectly into increased agricultural demand, excess utilisation of resources and the accompanying environmental impacts.15
In this vicious cycle, the environmental impacts of our diet are expected to intensify as the population grows from 7 billion to a predicted 10 billion in the next 30 years, and meanwhile the impacts of climate and environmental change are starting to make food production more difficult and unpredictable in many regions of the world.1,3 It’s a stark message, but unless dietary patterns change, by 2050 our unhealthy diets are likely to contribute to an anticipated 80% increase in agricultural GHG emissions and global land clearing.2
What is a sustainable diet?
Defining the concept of a sustainable diet is no easy feat and combines the challenges of creating a food system that supplies healthy, nutritious diets for a growing population whilst reducing its environmental impacts. According to the Food and Agriculture Organization of the United Nations, sustainable diets can be defined those diets with low environmental impacts which contribute to food and nutrition security and to healthy life for present and future generations. Sustainable diets are protective and respectful of biodiversity and ecosystems, culturally acceptable, accessible, economically fair and affordable; nutritionally adequate, safe and healthy; while optimizing natural and human resources.4
But how does this look in practice and what changes can we, as individuals make to ensure our own diets contribute to this sustainability? What, and how much we eat directly affects what, and how much is produced, so we can all play a pivotal role in adopting healthy and sustainable eating patterns to help address both health and environmental challenges.
It is a well-accepted and commonly held view that following a more plant-based diet is the most effective strategy for systematically reducing the GHG emissions and agricultural land use related to food production. This is not a new concept by any means and in 1971 the bestselling book “Diet for a Small Planet” argued that from a resource perspective, meat eating was highly ineffective and environmentally damaging.3
Producing plant protein generally uses less land, water and energy compared to producing animal protein, and animal products require more life cycle inputs per kilogram than plant products..6 For example, producing 1000Kcal of lamb or beef generates 14 and 10kg of GHG emissions respectively, compared with just 1kg and 3kg for the same amount of lentils and tofu, and producing just 1 serving of beef requires 1211L of water, compared with just 220 L to provide 1 serving of dry beans.9
The rearing of livestock for meat, eggs and dairy products is estimated to generate some 15% of total GHG emissions and monopolises 70% of agricultural land, including a third of arable land which could otherwise be used to produce crops. Animals grazing and indirectly, the production of animal feed are together key agricultural drivers of deforestation, biodiversity loss and land degradation.8 On average in the UK, a 2000kcal high meat diet was estimated to have 2.5 times as many GHG emissions than the average vegan diet – and two adults shifting from a high meat diet to a vegetarian diet for a year could save roughly the same carbon saving as running a small family car for 10,000 miles.13,14
Healthy plant-based diets are not only more sustainable but have also been associated with lower risk of chronic diseases such as obesity, type 2 diabetes, cardiovascular disease and some cancers. The term “plant based” encompasses a wide variety of dietary patterns that contain lower amount of animal products and higher levels of plant products such as vegetables, fruits, wholegrains, legumes and nuts and seeds.9
- Fruit and vegetables are rich sources of fibre, antioxidants, vitamins and minerals and have been inversely associated with risks of chronic diseases and mortality: indeed, a 200g/day increase in fruit and vegetable consumption has shown to increase the risk of stroke by 16%, cardiovascular disease by 8%, total cancer by 3% as well as providing a 10% lower risk of all-cause mortality.
- Wholegrains also serve as an excellent source of dietary fibre and other beneficial bioactive compounds, and one meta-analysis found a strong dose-dependent relationship between wholegrain consumption and consuming at least 70g of wholegrains daily was associated with around 20% risk reduction in cardiovascular disease, cancer and total mortality when compared to consuming little or no wholegrains.
- Legumes can also contribute to the reduction in chronic disease due to their high fibre, micronutrient and protein content and their intake has been associated with a lower risk of ischemic heart disease. Trials have also demonstrated that without changing body weight, increased legume consumption can lower total cholesterol, LDL cholesterol and triglycerides.9
While animal products are rich in protein and micronutrients, and as such can have a positive nutritional role to play in many people’s diets, it should also be mentioned that they are implicated, alongside other foods and lifestyle factors in the growing problem of obesity and chronic diseases and therefore reducing their consumption could benefit the health of the individual as well as the environment.
So which diet is best?
Although we have demonstrated that a more plant-based diet can have environmental benefits, evidence suggests that changing to a vegan, vegetarian or even flexitarian diet (predominantly plant-based diet with the occasional inclusion of meat or fish), unless properly managed, carries the risk of deficiency in certain micronutrients such as Vitamin B12, Choline and Calcium, which are currently supplied primarily through animal based products, and the addition of fruits, vegetables and legumes do not necessarily compensate for these nutrients.5 It should also be noted that just because a diet is more sustainable, doesn’t necessarily mean it is healthier and a vegan diet that consists of refined carbohydrates and added sugars such as juices/sweetened beverages, refined grains, potatoes/fries could put the individual at higher risk for weight gain and chronic disease including coronary heart disease and type 2 diabetes, than an omnivorous diet consisting of meat and a variety of healthy plant-based foods.9
The terms “vegetarian and vegan diets” can encompass a wide range of different dietary patterns and there is evidence that some can have a higher environmental impact than that of some omnivorous diets, which demonstrates the fact that when considering a sustainable diet, it is important to think in terms of individual dietary habits and the actual foods consumed. 11
Whist it is true that well managed vegetarian and vegan diets can afford many potential health benefits and with the support of appropriate supplements can provide a well rounded and comprehensive nutrient profile, cutting out whole food groups is unlikely to be manageable or appropriate for all of the population whereas striving towards a more plant-based diet is something we can all aim towards.
A systematic review of the alignment of various dietary patterns with environmental sustainability concluded that it is possible to achieve a sustainable diet that meets nutritional requirements without eliminating meat and dairy completely. Several different plant-based diets have been shown to reduce the risk of chronic disease, including the Mediterranean and Flexitarian diets, and all of these diets can include animal products such as dairy, and some even allow red meat in moderation – but all have been shown to be both healthier and associated with less environmental impact than the current standard Western diet.10
Although vegan and vegetarian diets undoubtedly have the capacity to dramatically reduce GHG emissions, it is estimated that a mere 25% reduction in meat consumption could minimise the impact of agricultural land expansion on ecosystems, biodiversity and carbon dioxide emissions. 6 One proposed strategy that aims balance the needs of nutritional health, ecological footprint and people’s personal dietary preferences is to encourage a global reduction in animal product consumption to 10% of daily calories: an amount approximately equivalent to 100g of animal product or one portion of meat about the size of a deck of playing cards.7
Contrary to much of the evidence, one study found that the vegan diet was not always associated with significantly lower environmental footprints when compared to a vegetarian diet. A likely explanation might be that in a hypothetical vegan diet animal-based products will be replaced with unprocessed, nutritious plant-based foodstuffs, whereas in reality it is often the case that the diets are high in highly-processed, high fat meat and dairy substitutes such as soy yogurts and vegan bacon and sausages. Moreover, the lower energy density of plant-based foodstuffs results in a higher food intake in a vegan diet when compared with a vegetarian (around 12.5% in terms of food weight) which could also contribute to reduced environmental benefits in some vegan diets.11 Likewise if, in a vegetarian diet meat is replaced with larger quantities of dairy, the environmental impact gains may be reduced or even eliminated and if meat is replaced with vegetables grown in high energy-demand greenhouses or out-of-season fruits flown from afar, any GHG emission offsets could be reversed. 12 This again demonstrates the need to consider the individual foods in whichever diet you choose to follow.
A Word on Waste
While being mindful of your diet is extremely important when trying to improve sustainability, food waste is also an important consideration as it embodies the sum of resources used to produce uneaten food, including cropland, agricultural fertilisers like pesticides and fertilisers and water for irrigation: these inputs being used to grow food that is ultimately wasted by the consumer. Globally, enough food is wasted each year to feed nearly 2 billion people a 2,100 kcal diet each day – a very sobering statistic indeed.16
While the evidence does suggest that higher quality, healthier diets also have less of an environmental impact, the production of fruit and vegetables wasted in high proportions carries environmental burdens as well, partially due to the relatively high rates of pesticides use and irrigation. Although higher levels of fruit and vegetables require far less land to produce than livestock, for example, they are typically wasted in much greater proportions than other food groups, thus reducing their benefits to the environment. In the developed world, more than 30% of food purchased is wasted, and if we were to reduce this figure, we would see a reduction in food production and corresponding reductions in land and water use and other inputs.12
So it becomes clear that although we should increase our consumption of plant foods, it is very important that we do so whilst simultaneously wasting less of them. This can be particularly challenging for individuals with limited time or money, including families with children and different food preferences, but by increasing the effort to plan meals ahead, we can reduce over-purchasing and ultimately reduce our food waste.
- Agriculture and food production have a huge impact on the health of our planet and our diets directly impact its future
- Our health and the planet’s health are intertwined and both need to be factored into a “sustainable diet”.
- Eating less animal products and more plant-based foods can be the most beneficial changes we can make for both the planet and our health
- While vegan and vegetarian diets can bring many environmental benefits, it is important to consider the individual foods consumed
- Food waste also contributes greatly to the environmental impact of our diets and should be reduced.
If you have questions regarding the topics that have been raised, or any other health matters, please do contact me by phone or email at any time.
Amanda Williams and the Cytoplan Editorial Team
- Springmann M, Wiebe K, Mason-D’Croz D, Sulser TB, Rayner M, Scarborough P. 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 Oct;2(10):e451-e461. doi: 10.1016/S2542-5196(18)30206-7. PMID: 30318102; PMCID: PMC6182055.
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- Gonzalez Fischer C, Garnett T. Plates, pyramids, planet. [Internet] 2016. Available at https://www.fao.org/3/i5640e/I5640E.pdf
- Burlingame B, Dernini, S. Sustainable Diets and Biodiversity: Directions and Solutions for Policy, Research and Action. [Internet] 2010. Available at https://www.fao.org/3/i3004e/i3004e.pdf
- Chen C, Chaudhary A, Mathys A. Dietary Change Scenarios and Implications for Environmental, Nutrition, Human Health and Economic Dimensions of Food Sustainability. Nutrients. 2019 Apr 16;11(4):856. doi: 10.3390/nu11040856. PMID: 30995719; PMCID: PMC6520741.
- Lynch H, Johnston C, Wharton C. Plant-Based Diets: Considerations for Environmental Impact, Protein Quality, and Exercise Performance. Nutrients. 2018 Dec 1;10(12):1841. doi: 10.3390/nu10121841. PMID: 30513704; PMCID: PMC6316289.
- Machovina B, Feeley KJ, Ripple WJ. Biodiversity conservation: The key is reducing meat consumption. Sci Total Environ. 2015 Dec 1;536:419-431. doi: 10.1016/j.scitotenv.2015.07.022. Epub 2015 Jul 29. PMID: 26231772.)
- Garnett T. Changing what we eat – A call for research and action on widespread adoption of sustainable healthy eating. [Internet] 2014. Available at https://www.oxfordmartin.ox.ac.uk/downloads/reports/FCRN%20Wellcome%20GFS%20CHANGING%20CONSUMPTION%20REPORT%20FINAL.pdf
- Hemler EC, Hu FB. Plant-Based Diets for Personal, Population, and Planetary Health. Adv Nutr. 2019 Nov 1;10(Suppl_4):S275-S283. doi: 10.1093/advances/nmy117. PMID: 31728495; PMCID: PMC6855934.
- Nelson ME, Hamm MW, Hu FB, Abrams SA, Griffin TS. Alignment of Healthy Dietary Patterns and Environmental Sustainability: A Systematic Review. Adv Nutr. 2016 Nov 15;7(6):1005-1025. doi: 10.3945/an.116.012567. PMID: 28140320; PMCID: PMC5105037.
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- Fresán U, Sabaté J. Vegetarian Diets: Planetary Health and Its Alignment with Human Health. Adv Nutr. 2019 Nov 1;10(Suppl_4):S380-S388. doi: 10.1093/advances/nmz019. PMID: 31728487; PMCID: PMC6855976.
- Scarborough P, Appleby PN, Mizdrak A, Briggs AD, Travis RC, Bradbury KE, Key TJ. Dietary greenhouse gas emissions of meat-eaters, fish-eaters, vegetarians and vegans in the UK. Clim Change. 2014;125(2):179-192. doi: 10.1007/s10584-014-1169-1. Epub 2014 Jun 11. PMID: 25834298; PMCID: PMC4372775.
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- Heller MC, Keoleian GA. Greenhouse gas emission estimates of U.S. dietary choices and food loss. J Ind Ecol. 2015;19(3):391–401.
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