Measuring land use impacts of national dietary guidelines: a scoping review of methods, trade-offs and policy...

Background. As agriculture uses a substantial proportion of the world's habitable land, it is important to consider how the food we eat, and different dietary patterns, impact the pressures put on land. Aim. This scoping review aims to 1. explore the approaches to measuring potential land use impacts of aligning diets or the food supply with national dietary guidelines, 2. summarise the additional environmental factors included in these studies, and specifically how often biodiversity is included, 3. identify policy recommendations made. Method. The Joanna Briggs Institute scoping review framework was used to identify studies measuring potential land use changes of shifting national diets or the food supply towards national dietary guidelines. Only official national dietary guidelines were included. Due to heterogeneity in how dietary and environmental impacts were calculated, results are represented in terms of increases and decreases, rather than average percentage change. Results. Of the forty-five papers included, only 4 measured biodiversity impacts, compared to 35 measuring greenhouse gas (GHG) emissions, 24 water, and 10 fertiliser use. Most studies used life cycle assessment to measure the potential land use and environmental impacts. All studies found an increase in fruit and vegetables would be needed to meet dietary guidelines, and all but two found a reduction in meat is required. Papers mostly reported reduction in resource in land use and GHGs (28/45 and 22/35 papers, respectively). Impacts on water, energy and biodiversity, which were less frequently included, were more mixed. Over half of the papers included policy recommendations (n = 29), with the most being to incorporate sustainability into dietary guidelines. Conclusion. A wider range of environmental outcomes should be included when assessing the environmental sustainability of dietary changes to get a more holistic view of the potential trade-offs and co-benefits that need to be navigated with these dietary shifts.