Scientific Study

Debate persists around the food production and dietary changes needed to improve sustainability of our global food system. We reviewed 29 studies in high-income countries that used various methodologies to define a healthier, more sustainable diet. Diets aligned with dietary guidelines, containing less meat and higher amounts of plant-derived foods (vegetables, pulses [beans/lentils], fruit, wholegrains, nuts, seeds) would likely offer environmental benefits (~20–50% lower greenhouse gas emissions [GHGE] and land use) and improve population health, although may not reduce water footprint. Changes in consumption of milk products and eggs were inconsistent in optimisation studies, perhaps reflecting trade-offs between their nutrient contribution and environmental impact. Foods high in fat, salt and/or sugar, and beverages (e.g. tea, coffee and fruit juices) contributed substantially to environmental footprints in some studies. Vegetarian and vegan diets may deliver larger environmental benefits, but are unlikely to be widely adopted, and may reduce intakes and/or bioavailability of some essential nutrients (e.g. iron, zinc, iodine and B12). We recommend adherence to existing government dietary guidelines as a more realistic goal to improve environmental (e.g. 30% lower GHGE in the UK) and health impacts of diets, recognising that adherence is currently relatively poor. Wider considerations include: context-specific nutritional, health, cost and cultural needs; need for public engagement to understand barriers/motivators; better understanding of the wider implications and trade-offs linked to dietary and food system changes and how these can be managed, so that benefits in high-income countries do not come at the expense of greater ‘outsourced’ environmental impacts in other regions. https://doi.org/10.1111/nbu.12518