Sustainable diets are a hot topic at the moment. It’s almost impossible to turn on the television, scroll your social media feed, or flick through a glossy mag without encountering advice about what you should - and shouldn’t - be eating to save the planet.
We are told that individual dietary change is an easy and essential step as we transition to a more sustainable way of living.
The reality, of course, is a little more complicated.
Most studies into the environmental impact of food production focus on just one metric - often the associated greenhouse gas (GHG) emissions - and fail to consider other aspects such as water and land use.
CSIRO’s Dr Bradley Ridoutt is a research scientist whose expertise is life cycle sustainability assessment in the agriculture and food sectors. He believes that we need a broader approach, and that simplified messaging around what constitutes ‘sustainable eating’ often ignores the problems that are encountered when trying to achieve multiple environmental objectives along with a healthy, high quality, diet.
“There has been a big focus on food that produces the most emissions,” says Dr Ridoutt. “Emissions are certainly an important consideration, but in Australia particularly – the driest inhabited continent – we need to be taking a more scientific approach and thinking about water too.”
Alongside colleagues in CSIRO’s Nutrition & Health Program, Dr Ridoutt has recently published a paper in the journal Sustainable Production and Consumption that explores the potential for achieving healthy diets within planetary boundaries – in other words, diets that are the result of food systems that do not exceed the limits for natural resource use and emissions.
The (hidden environmental) cost of food
Dr Ridoutt’s method was to develop a weighted Environmental Impact (EI) score, which in addition to GHG also takes into account the water-scarcity footprint and cropland-scarcity footprint of each food. Cropland is an area of concern because ploughing new lands for crop production entails the loss of forest and grassland, threatens biodiversity, and disturbs water and nutrient cycles.
The EI scores were calculated for a large number of processed and unprocessed foods in the Australian food system, and then used to assess more than 9000 individual Australian adult diets obtained from the Australian Health Survey. Crucially, a diet quality score, assessing the compliance with the Australian Dietary Guidelines, was also applied.
The resulting data was then used by Dr Ridoutt to assess the potential for dietary change to concurrently reduce environmental impacts and improve diet quality.
“What we found was that yes, you can reduce your environmental impact to some extent through dietary choices – but it’s really a very modest change, and when there are multiple objectives they tend to constrain each other. We’re not just looking to achieve a sustainable diet; rather we’re looking to achieve a sustainable, healthy diet – and that’s significantly more challenging.”
Dr Ridoutt and his colleagues also discovered that while it was possible to identify dietary patterns that scored well for one of the metrics, there were often significant trade-offs involved. The dietary model that achieved the largest climate impact reduction resulted in the largest water-scarcity footprint tradeoff.
The complexity of value chains
When it comes to analysing the environmental impact of different foods, an additional complexity that often goes unaddressed is the role of highly processed foods. There is a tendency in many studies to focus only on the agricultural production phase, which excludes the resource use associated with manufacturing and processing.
“Agriculture is easiest to research because we can model farming systems, but it’s what comes after the farm and further down the supply chain that can sometimes have the biggest impacts,” says Dr Ridoutt. “Individual companies have different practices, leading to varying levels of water and energy use. If you ignore that, you can easily end up with an analysis that might favour foods made from highly refined ingredients and makes wholefoods look unsustainable, when in actual fact it’s the other way round.”
Dr Ridoutt and his colleagues avoided this potential bias by undertaking a ‘cradle to food producer’ analysis which included processing but excluded packaging. Taking this comprehensive approach results in more accurate data from a diet quality perspective as well as a sustainability one: for example, it allows a distinction to be made between potatoes that are eaten baked or boiled and counted as a healthy, core food, and potatoes that have been processed into crisps or fries and are counted as discretionary or an unhealthy food.
A future focus on Australia’s fondness for discretionary foods seems like a potentially fruitful area of common ground between sustainability advocates and nutritionists. They were the largest contributor to the EI score, at 28.9 per cent, and are also a key contributor to poor nutrition, as they are energy-dense and nutrient-poor.
At an individual level, perhaps the single most important thing you can do - for the planet’s health and for your own – is to reduce your intake of highly processed discretionary foods.
However, the key message from Dr Ridoutt’s research is less about the role of individual diets, and more about the changes that are required in the food production system if we want to eat more sustainably.
“The potential for individual dietary choices to force change is limited,” he says. “In Australia, you simply can’t eat a climate neutral diet. The required variety of climate neutral foods is not available to enable this. So, the work needs to be done on the production side of the equation more than the consumption side. It’s already happening to some extent – but farmers and the agricultural industry need support and encouragement. Priority needs to be given to innovation to make lower-impact food choices available. We can – all of us – only eat what’s available.”