The challenges of defining a healthy and ‘sustainable’ diet

Abstract

Considerable debate exists about changes required to current diets to deliver simultaneous improvements for both human health and environmental sustainability. Media coverage has focussed largely on the environmental and health impacts of animal source foods, particularly red meat. However, animal source foods contribute notably to intakes of micronutrients (e.g. iron, zinc, iodine, calcium) in current UK diets, and evidence indicates nutrient intakes/status may be inadequate if appropriate substitutions are not made when restricting such foods in the diet, highlighting the need to consider the overall dietary pattern. Healthy and sustainable dietary patterns have been modelled based on nutritional adequacy alone (e.g. Eatwell Guide), or nutrition combined with environmental impact (e.g. WWF Livewell Plates). Studies have also considered other aspects, such as the health impact or cost, with some analyses providing ‘optimised’ diets representing the smallest required changes to current diets. Consistent changes are evident for most food groups (e.g. increases in fruit and vegetables, starchy carbohydrates, fish and – in most cases – beans, pulses and other legumes; decreases in red/processed meat, cheese and high-fat/sugar foods). However, recommendations for dairy consumption (particularly milk) are less consistent. Methodological variation makes it difficult to directly compare recommendations to date, due to use of different data sources, environmental metrics and modelling assumptions/constraints, although reducing food waste is an important consideration regardless of dietary pattern. In the UK, adopting the government’s Eatwell Guide, which incorporates affordability and familiarity, appears a sensible direction of travel at the current time, likely to deliver nutritional, health and environmental benefits.