The environmental and nutritional attributes of different food types can vary greatly. Consequently, diets composed of different sets of food types, will differ in their environmental footprints, and in their nutritional quality; so affecting human health. When such differences are multiplied by many millions of people, the overall effect is considerable.
Human diets are, therefore, an important point of interconnection in food systems via which change is driven – for better or worse – by shifts how people consume. At least in theory, diets might provide a means by which to achieve both health and environmental goals simultaneously. But the reality is not so simple.
Understanding these complexities, helps provide a window on both the opportunities and difficulties of taking a food systems approach, and on the important role that diets play.
The chapter addresses the following:
- What would make an eating pattern sustainable and healthy?
- What dietary patterns would contribute to fewer GHG emissions and other environmental impacts, and are these necessarily healthier, or closer to recommended healthy diets?
- How do the multiple environmental, health, societal and cultural aims of “sustainable healthy eating patterns” support or conflict with one another?
- When attempting to define sustainable healthy eating patterns (SHEPs) it is important to consider that “sustainable” is in itself a difficult concept to define; as is a “healthy” diet. Both of these concepts are multifaceted, with some aspects receiving more attention. Combining them complicates things further.
- Definitions of SHEPs exist, but these tend to list things they should account for, such as nutrition and health, biodiversity protections, optimisation of natural and human resources, affordability, availability and cultural relevance. This does not give us tools to measure which eating patterns are better for health and sustainability.
- For the idea of SHEPs to be useful, we need to be able to say what they look like on a plate. This requires the development of metrics and methodologies to measure the many different attributes of diets, and understand the ways in which they affect people, and the wider world.
- Our ability to measure these different attributes is still limited. Most research has focussed on greenhouse gases, land, and water footprints via the application of life cycle assessment methods; and on nutritional quality and health outcomes by looking at clinical studies of real diets. Some things such as cultural impacts are extremely hard to quantify and compare, but are still important.
- Multiple studies have shown that healthy diets (as defined by government guidelines), and nutritionally balanced diets containing less or no meat or animal products, are associated with significantly reduced levels of greenhouse gas emissions and associated land-use.
- Whether a dietary change brings benefits for health and sustainability, depends on what foods are removed, and what they are then replaced by (if at all). For example, replacing sugary snacks with fruits and vegetables may improve health, but increase greenhouse gas emissions.
- While not inevitable, diets that are healthier and more sustainable that today are possible for many people in many contexts. Although what they actually consist of will vary depending on the individual's specific bodily characteristics, their cultural context, and the socio-economic and environmental characteristics of where they live.
- There are also many instances where an improvement in one dimension of a diet with respect to health or environmental outcomes, can lead to increased impacts in another: i.e. a trade-off. Similarly, there may be trade-offs between different environmental outcomes (e.g. lower emissions but greater water use).
- For many, typically in high-income countries, meat and dairy are over-consumed, and consumption of fruit, vegetables, pulses and whole grains is below recommended levels. Making these substitutions would result in decreased environmental impacts, and improved health.
- Many people, often in lower-income countries, do not have sufficient dietary diversity and so would benefit from more meat and dairy, as well as more fruit and vegetables. Making these substitutions or additions to their diet would benefit health, but likely increase the environmental impacts of their diet.
- In high-income countries, significant reductions in GHG emissions can be achieved by average changing diets across the population. But achieving cuts beyond ~40% in an individual's diet-related emissions, may require changes that are culturally unacceptable, and so may not be realistic.
- While general trends can be outlined already, our understanding of sustainable health eating patterns is still developing and is highly uncertain. This makes context specific recommendations difficult to provide. Much more research is needed for the concept to be able to be put into practical use worldwide.
Tara Garnet, FCRN, University of Oxford
Jess Finch, FCRN, Warwick University;
Dr Peter Scarborough, University of Oxford;
Samuel Lee-Gammage, FCRN, University of Oxford;
Marie Persson, FCRN, University of Oxford;
Professor Mike Hamm, Michigan State University;
Dr Elin Röös, Swedish Agricultural University;
Dr Tim Hess, Cranfield University;
Professor Tim Key, University of Oxford;
Professor Tim Benton, University of Leeds;
Professor David Little, University of Stirling;
Professor Peter Smith, University of Aberdeen;
Mara Galeano Carraro.
Any inaccuracies and errors, remain the responsibility of the FCRN.
The production of this chapter was enabled by funding from the following sources:
The Daniel and Nina Carasso Foundation;
The Oxford Martin Programme on the Future of Food;
The Wellcome Trust;
The Esmée Fairbairn Foundation;
Waste Resources Action Programme (WRAP);
The Sustainable Consumption Institute at Manchester University.