Sustainable diets are becoming a factor that increasing numbers of us consider when doing our weekly food shop. However, it is a pretty complex and confusing concept, with many disagreements over what constitutes a sustainable food. Should we be eating a completely vegan diet? One that only uses local ingredients, including meat? Farmed, wild or no seafood? and what does this look like when we take healthy diets into consideration? The FAO’s definition of sustainable, healthy diet is one that “promotes all dimensions of individuals’ health and wellbeing; have low environmental pressure and impact; are accessible, affordable, safe and equitable; and are culturally acceptable”(1). I think the inclusion of points that emphasise the importance of diets being both affordable and culturally acceptable is really key. It is very easy to find oneself in a dietary bubble or echo chamber and to forget the factors that come into dietary decision making for others.
There are three main aspects that are measured to assess sustainability of foods: carbon and greenhouse gas (GHG) emissions; land use; and water. The interplay between these factors is one source of disagreement between which of two foods is more sustainable. Moreover, heavy watering, deforestation and international shipping or flying of foods are very visible forms of environmental impact; GHG emissions from the field or barn can feel more abstract.
Carbon emissions are often the factor most referred to when comparing how environmentally food products are. Carbon emissions are produced during the growing, rearing, farming, transporting of the plants, animals and products that we eat, as well as their storage, cooking and disposal. As such, estimating the carbon footprint of a food is tricky, and subject to huge variation. Some brands, such as Oatly, may display their carbon dioxide equivalent per kg of product. The carbon footprint of foods is often used as the main form of assessing sustainability. It gives a good idea of the energy that is required to go in to producing a food, however it is by no means the only factor to be considered when deciding whether a food is sustainable.
Some foods require more water to be produced than others, with chocolate, meat and dairy having a higher water demand than potatoes or oats. For some crops, location is key. The water demand of almonds grown in dry California is exceptionally high per weight of product produced, but nuts grown in naturally wet climates may need no additional irrigation at all (2).
Animal-based foods tend to have a higher demand for water, and greater output of carbon as to raise an animal, you need to provide it with water, grains and other foods, which will have in turn needed resources to grow. In this respect, it is easier to compare foods looking at just carbon and water, and using this, plant-based foods will often be seen as more sustainable than animals, simply because of removing an energetic step in the food chain. When eating plants, you only need to put water and energy into feeding and harvesting the crop. When eating animal products, you need to put energy into growing those crops for the animal to eat as well.
This is where sustainable food becomes harder to quantify. Intensive crop monoculture will deplete soil of nutrients if farmed improperly. In contrast, manure from farm animals can return nitrates to the soil. One method of animal husbandry is “mob grazing” where a farmer divides their land into several smaller fields to keep cattle in, and moves the cows on every few days so that they are always grazing on fresh grass. Some days after the cows have been in a field, chickens are let loose, and they can both feed on potential parasites, and work cow pats into the soil, improving the structure and nutrient content. There are many different agricultural practices, some involving animals, some not, that are based around improving the quality and condition of the land.
In terms of land use, more land is required to raise animals than to grow crops. This can be reduced by housing animals in barns instead, but this raises ethical implications, especially when this is a year-round practice offering animals very little space. On the other hand though, animals can be raised on land inappropriate for crop growth, such as sheep living on upland areas of the UK. Then, there is also the question of wild animals, who require little or no actions of humans to live, and in some cases, such as deer, there may already exist a cull quota due to a lack of natural predators to maintain population size at an ecologically healthy level.
It is impossible to prescribe a perfect sustainable diet. There are several ways to eat sustainably, which are influenced by geographic location, cultural and ethical factors, and unique dietary requirements. Many people do not have the privilege of being selective about their diet, and those of us who are should not shame those who have less freedom of choice. Where possible, inclusion of more plant foods can be a positive step for the environment, and for health.
For centuries, eating meat was a luxury reserved for the wealthy, or perhaps only for a few meals. That joint of beef or whole chicken served in a classic Sunday roast might be the only piece of meat bought in a week, and could be stretched to several meals. This mentality is one that many of us could look at adopting. Buy a little less and make it last longer. If you’re eating a little less animal products, and are able to chose what you buy, you might look to prioritise meat grown locally, from farms utilising more sustainable practices.
For those of you who use dairy-free milk alternatives, you might swap almond milk for oat. You can still enjoy avocado on toast, but maybe consider buying slightly less per week. Whilst seasonal food gets put on a bit more of a pedestal than it perhaps deserves, favouring in-season food can reduce your food miles, and give you a greater appreciation for flavour of fresh, local produce, and the diversity of the seasons offering’s.
Much of sustainable food is about exploring what options fit best with your lifestyle, ethics and tastes rather than rigidly sticking to views presented from one camp or another.