What Does a Sustainable Diet Look Like?

sustainable diet

It can be hard to know exactly what a sustainable diet looks like. For instance, a study from the University of Oxford, published in Climatic Change, found that the vegan diet produces the least greenhouse gas emissions. Comparisons were made between meat-eaters, fish-eaters, vegetarians, and vegans. In this way, a plant-based diet would be considered the most sustainable. But is it not possible to include some animal products in one’s diet in a sustainable way? After all, the flexitarian diet, which involves the occasional consumption of fish and meat, may also be sustainable. This is because – referring back to the Oxford study – low meat-eaters have a significantly lower carbon footprint compared to high meat-eaters, and only a slightly larger footprint compared to a vegetarian diet.

We can also look at how countries differ in their dietary guidelines to get a sense of whether government recommendations on diet are actually sustainable. Comparing the dietary guidelines of the US and the Nordic countries will be illuminating in this regard, as their recommendations differ in some significant ways in their ecological ramifications. These guidelines are based on what to include in your diet and what to limit in order to stay fit and healthy. It’s up for debate whether these guidelines promote balanced and accurate information. But a crucial component of diet that is often left out of these guidelines is sustainability. The Nordic diet recommendations, as we will see, stand out as having a positive ecological impact.

USDA Dietary Guidelines Do Not Promote a Sustainable Diet

If we wanted to grow enough food to feed the entire world according to United States Department of Agriculture (USDA) dietary guidelines, then we would need an area of arable land the size of Canada (3.8 million square miles). This goes to show that these guidelines promote an unsustainable diet – it puts immense pressure on our natural resources. A 2018 study, published in PLOS One, analysed crop data and yields at national, continental, and global levels. The researchers wrote:

Our analysis shows that there is not enough land for the world to adhere to the USDA guidelines under current agricultural practices. This is despite the fact that the USDA guideline diet is already less land-intensive than the current U.S. diet.

The standard North and South American diets are very high in animal products, which entails all kinds of environmental damage. Yet even if everyone in North and South America restricted their meat consumption to the more moderate levels recommended by the USDA, there still wouldn’t be enough land in the world to meet their agricultural needs. This suggests that health can’t be the only factor taken into account when devising dietary guidelines.

Nordic Recommendations

The latest Nordic eating guidelines – those that apply to Denmark, Finland, Iceland, Norway, and Sweden – were published in 2018 and include the following recommendations:

  1. Eat more fruit and vegetables every day
  2. Eat more whole grain produce
  3. Eat more food from the seas and lakes
  4. Eat higher-quality meat, and less of it
  5. Eat more food from wild landscapes
  6. Eat organic produce whenever possible
  7. Avoid food additives
  8. Eat more meals based on seasonal produce
  9. Eat more home-cooked food
  10. Produce less waste

The World Health Organization conducted a review of the Guidelines for the New Nordic Diet (NDD) and found that it was effective at preventing non-communicable diseases, which consist primarily of cancer, cardiovascular diseases, chronic respiratory disease, and cancer. These diseases are the leading cause of death on a global scale, so WHO praised the NDD, as well as the Mediterranean diet, for its healthfulness. WHO also noted the impressive environmental benefits of the NDD. Its review stated that the Nordic countries have:

adopted a collaborative regional approach within the wider Region to improve the diet, reduce production and consumption impacts on the environment, increase intervention sustainability and facilitate the achievement of the SDGs [Sustainable Development Goals].

Changing our diets is just one aspect of making the human presence on the planet sustainable. Even if we halted all our emissions tomorrow (not just from diet, but in general), we would not avoid all the harmful effects of climate change. However, this could help us avoid the most severe effects; and furthermore, with the current population, which is exponentially growing, a sustainable diet will have to be one that does not over-exploit the planet’s precious resources, such as water and arable land. Drastically cutting meat consumption is recommended as a way to eat more sustainably. Widespread veganism would be ideal, since this diet is associated with the least amount of emissions, but could normalised flexitarianism also be sustainable? The Nordic recommendations are sensible and evidence-based, but they are not specific or comprehensive enough. Calls to ‘eat less’ or ‘eat more’ of a certain type of food are vague. What constitutes sufficiently ‘less’ or ‘more’ that would be part of a genuinely sustainable diet?

Does a Sustainable Diet Need to Exclude Animal Products?

Chiara Vitali, Forests Campaigner from Greenpeace UK, states that if we want to avoid climate breakdown in an evidence-based way, then we need to reduce the amount of meat and dairy we consume by about 70%. These dietary changes would go beyond a flexitarian diet (or casual vegetarianism) since the latter does not involve occasional consumption of dairy, only meat and fish. It may be, then, that we need to adopt a flexi-vegan diet, whereby you don’t consume animal products very often, as it is these types of foods that tend to carry the highest carbon footprint.

A potential issue with any current dietary recommendation aimed at sustainability is that it does not take into account factors like population growth and changes to technology and energy systems, all of which can affect the sustainability of a diet (so dietary recommendations should either reflect this or be open and flexible). For instance, if the population continues to increase dramatically, projected to reach 10.9 billion by 2100, then a 70% reduction in meat and dairy may no longer be sufficient. If animal agriculture exists in its current form by that time, then even greater reductions will be necessary to make one’s diet sustainable, or perhaps the complete elimination of animal products will be recommended.

Also, despite promises that lab-grown meat (or cultured meat) will make regular meat-eating sustainable, research suggests artificially grown beef may not be better for the environment than cattle farming. In fact, cultured meat production meats require larger energy outputs over the long-term (if energy systems rely on fossil fuels), which will make this much-hyped meat unsustainable. This is because the environmentally damaging methane produced by cows stays in the atmosphere for a shorter amount of time than the carbon dioxide that would be created through lab-grown beef. Dr John Lynch, the lead author of this 2019 research, stated: “The climate impacts of cultured meat production will depend on what level of sustainable energy generation can be achieved, as well as the efficiency of future culture processes.”

Thus, it is possible that a diet including the regular consumption of meat could be sustainable if cultured meat production methods are improved. But if these production methods cannot be made sustainable, the occasional consumption of animal products (70% less than standard consumption levels) could still be sustainable, so long as the global population was brought under control. However, it is far easier to imagine food productions becoming sustainable, through a shift towards renewable or nuclear fusion energy, than it is to picture a stabilisation or reduction of the global population (achieved either voluntarily or through policy measures).

There is also the argument that the introduction of a meat tax – a tax that takes into account the environmental damage associated with meat – would help promote sustainability. And indeed, studies illustrate that the environmental benefits of such a tax (15% or 30%) would be enormous. This is because the revenue generated from a meat tax could go towards subsidies on fruit and vegetables, bringing down the price of these foods, thereby increasing their consumption and the environmental benefits associated with this behaviour. This revenue could also go towards other environmental projects that aim to cut emissions. Similar arguments are made in favour of carbon offsetting, which is when you try to compensate for your carbon emissions (e.g. through flying) by funding carbon dioxide reducing projects (e.g. tree planting). However, carbon offsetting is not a simple solution, nor is it the most effective one for our ecological woes. For example, it is difficult – perhaps impossible – to know if funding a particular environmental project can actually compensate for the harm caused by, say, flying. The exact extent of harm is not necessarily balanced out by the funded benefits. The same criticism could be levelled against a meat tax proposal. Would subsidies for fruit and vegetables really nullify the issues associated with meat production?

A vegan diet would be ideal from a sustainability perspective. A global shift towards a plant-based diet could sustainably feed 10 billion people, according to a study published in Nature. In fact, we already produce enough calories to feed 10 billion on the planet; the reason so many people aren’t sufficiently fed is that the majority of these calories go towards livestock, which is a highly inefficient way to produce food. Worldwide flexi-veganism could be sustainable too if followed consistently and within certain parameters. The problem with this solution, however, is that trying to achieve, say, a 70% reduction in animal products is, in some ways, practically harder than the elimination of animal products. How are we to track whether or not we are achieving this 70% reduction? On the other hand, loosely following a significant reduction (maybe 50% some weeks and 90% in other weeks) could be sufficient. Flexi-veganism would be sustainable up to a certain point of population growth, but this limit would be met sooner than with a vegan diet. It is possible that, with flexi-veganism, greater reductions in animal products would be needed over time (i.e. 70%, then 80%, then 90%), until a fully vegan diet is recommended.

As we have seen, sustainable lab-grown meat could make meat-eating sustainable. But diets heavy in farmed animal products are unlikely to ever be sustainable unless a serious reduction in population is achieved. Lastly, the meat tax debate is a tricky and contentious one, and it is not clear whether such a tax, in itself, would be enough to make meat-eating sustainable (this would depend on how high the tax is, how the tax changes meat consumption, and if – at all – revenue from the tax can adequately ameliorate the emissions from meat production and other harmful environmental effects). 

Promoting Sustainable Diets

Food policy expert Tim Lang and nutritionist Pamela Mason have co-authored a book titled Sustainable Diets: How Ecological Nutrition Can Transform Consumption and the Food System. They argue that people in both developed and developing countries need to transform their diets, for both environmental and health reasons. Poorer countries are now adopting the American diet, which is heavy in cheap, processed meat, dairy and refined carbs. We know that this kind of diet is not sustainable.

The authors state it is clear from the available evidence that people need to increase their intake of plant-based foods – including fruits, vegetables and whole grains – and limit their consumption of meat and processed foods high in sugar. But they also define a sustainable diet as one that prevents socio-economic divisions, such as those caused by economic inequality, bad governance, poor wages, and lack of education. Mason argues that a certain amount of ignorance can explain why so many people are failing to transform their diets. She lays the blame on the food industry:

Consumers are largely ignorant of how many ticking time bombs there are within the food system. Many supermarkets and food processors know but are acting below the radar, when it is time for them to come clean with the public and to engage people in the change.

People are also worried that changing their diets, in a way that reduces meat and includes more fruit and veg (or which shifts towards veganism), will be expensive. Undoubtedly, fast food is affordable. But this attitude reflects a common misconception about sustainable diets. They’re not actually expensive. In fact, they can be cheaper than a diet heavy in animal products. As a case in point, data collected by Kantar reveals that vegan meals are, on average, 40% cheaper than meat or fish equivalents. This is true despite the fact that meat is heavily subsidised and fruit and vegetables aren’t. A vegan diet can easily be affordable because staple foods like beans and rice are some of the cheapest foods that exist.

Some countries are doing a better job than others in helping consumers change their eating habits. Mason and Lang claim that only Sweden, Germany, Brazil, and Qatar have been acting effectively in this regard. Part of the problem lies in the fact that meat and dairy lobbies can block attempts to introduce sustainable dietary guidelines. Lang, who is a professor at the Centre for Food Policy at City, University of London, states:

Humanity is entering a new era for food consumption. The new goal for consumers is to eat low impact diets. Only sustainable diets will give future generations the chance of decent living. It is a fantasy to say we can produce our way out of the coming crunch.

It can be difficult to change your diet when you’re just thinking about carbon emissions. Even if you know that eating beef is more significantly more environmentally harmful than eating beans, this can still seem very abstract. However, we can see the real effects of unsustainable diets in the form of extreme weather events (e.g. flooding, slides, tornadoes, cyclones, and hurricanes). One study highlights that carbon emissions from human activity are linked to extreme weather, which can result in many human lives being lost and ruined. Our diet is implicated. And as Lang stresses, it’s not only present human lives that are at stake but the lives of future generations as well. People need to make the connection. The food on our plates, therefore, is one crucial aspect of the climate crisis that is threatening our very existence.

A holistic and strongly risk-averse response to the climate crisis would be organic plant-based farming (also called ‘veganic farming’), alongside replacement level fertility (when a population exactly replaces itself from one generation to the next – to achieve this, the total fertility would need to be 2.1 children per woman). But of course, this is not the only viable solution. Lab-grown meat has the potential to be a sustainable alternative, one that also does away with the most egregious forms of animal exploitation. However, lab-grown meat does not necessarily entail the elimination of animal exploitation since it would depend on the use of a small number of non-human animals (we would still need live animals to extract cells from, which would then be used to artificially grow meat). If our aim is to reduce both animal suffering and environmental harm as effectively as possible, then a vegan diet seems to be the most logical option.

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