- Generally meat and dairy are always seen as the most environmentally damaging foods.
- Widely cited figures don't take into account nutrient density. Not an accurate or useful measure.
- Meat and dairy very nutrient dense. Need to account for this in sustainability measures.
- Meat and dairy are ready source of key nutrients and can still be part of a sustainable diet.
Almost everywhere you look, people are sharing figures about the carbon footprint of different foods and using seemingly concrete evidence to make strong claims about what a sustainable diet should look like. At first glance, these figures seem to tell a clear cut story. However, as I'm about to explain in this month's blog, all too often, this is just not correct.
How many times have you seen a graph showing the relative carbon footprint (emissions intensity) of a kilo of different foods? Generally, beef, lamb and dairy are at the top, with vegetables, beans and pulses towards the bottom.
The most commonly cited study is by Poore and Nemecek (2018) who conducted what is generally seen as the largest meta analyses of food systems environmental data to-date. This study is cited time and time again by policymakers, activists and concerned individuals.
Unsurprisingly, their results show beef, lamb and cheese at the top of the emissions table. In fact, based on their data, the emissions associated with a kilo of beef are over 31 times greater than a kilo of tofu. As such, many proponents of a plant-based diet cite this as clear evidence that meat and dairy should be eliminated from our diets.
However, whilst this may seem like fairly damming evidence against animal-derived foods, it's absolutely vital to add some context to these numbers. Firstly, these are global average figures, taking into account the very worst and very best production systems.
In the UK for example a typical emissions figure for a kilo of beef is generally around 20-30 kg CO2e/kg beef* as opposed to the whopping 99.48kg CO2e. quoted by Poore & Nemecek. These global figures account for direct land use change for example, from cattle production in South America that is linked to Amazon deforestation, something that is not the case for UK beef producers.
Whilst there are of course still emissions associated with livestock and dairy production in the UK, in reality they are nowhere near the level this study would suggest.
In fact, for beef producers in temperate regions like the UK, through practices like careful management of pasture to sequester (lock up) maximum carbon and eliminating the feeding of imported grain to cattle, it's possible to produce beef with a relatively low carbon footprint.
In some cases there are even farms that are sequestering more carbon each year than their animals emit, which means they are at or below net zero. This is not something taken into account by studies like Poore & Nemecek that produce global average figures.
However, regional differences in emissions aside, there's an inherent flaw with studies like this, that simply compare the emissions of a kilo of one food against another. Each food is unique in its nutritional composition and other characteristics, therefore, a kilo of spinach can't and shouldn't be compared to a litre of milk.
The point of food is to nourish and sustain you, not just to tick a box on a spreadsheet. Reducing discussion on the sustainability of different foods to simply comparing total emissions, completely overlooks all of this.
Much of the population in the UK are poorly nourished, not through lack of food, but because of the wrong food. Therefore any discussions on "sustainable" diets need to take the relative nutrient density of food into account too.
Foods like spinach, beans and tofu (or muesli) are full of essential nutrients, but you may need to eat a lot more of these foods to get the same amount as meat, dairy or eggs. Are these nutrients as bioavailable to your body in all food types?
Enter Katz-Rosene et al. (2023). Their recent study aims to overcome this analytical challenge by coupling a Lifecycle Assessment (LCA) with a measure of priority micronutrient value to assess different foods. I would encourage everyone to take a moment to look at this, because it's absolutely fascinating.
While (most) red meat is still high up the list of emissions, when nutrient density is taken into account, by far the most emissions intense foods are 1.palm oil, 2.olive oil and 3.chocolate. Milk, eggs and liver fall way down the list, below many plant-based foods.
As a basis for informing consumers to adopt a more sustainable diet (in the broadest sense), a measure like this is absolutely essential. Just focusing on total emissions per kilo of food may well lead to poorer nutritional outcomes, with limited environmental benefit.
I have no issue with those who choose not to consume meat or dairy, but from a farming perspective (see previous blogs), integration of livestock into sustainable crop production systems is absolutely essential. What studies like Katz-Rosene et al. show us, is that as well as being a fundamental part of a low input farming system, meat and dairy (in moderate quantities) can also be an efficient source of nutrient-dense food.
*I spend my working day measuring the carbon footprint of farming systems. Trust me on this.