Achieving dietary recommendations and reducing greenhouse gas emissions: modelling diets to minimise the change from current intakes

International audienceBackground: Average population dietary intakes do not reflect the wide diversity of dietary patterns across thepopulation. It is recognised that most people in the UK do not meet dietary recommendations and have diets witha high environmental impact, but changing dietary habits has proved very difficult. The purpose of this study wasto investigate the diversity in dietary changes needed to achieve a healthy diet and a healthy diet with lowergreenhouse gas emissions (GHGE) (referred to as a sustainable diet) by taking into account each individual’s currentdiet and then minimising the changes they need to make.Methods: Linear programming was used to construct two new diets for each adult in the UK National Diet andNutrition Survey (n = 1491) by minimising the changes to their current intake. Stepwise changes were applied until(i) dietary recommendations were achieved and (ii) dietary recommendations and a GHGE target were met. First,gradual changes (≤50 %) were made to the amount of any foods currently eaten. Second, new foods were addedto the diet. Third, greater reductions (≤75 %) were made to the amount of any food currently eaten and finally,foods were removed from the diet.Results: One person out of 1491 in the sample met all the dietary requirements based on their reported dietaryintake. Only 7.5 and 4.6 % of people achieved a healthy diet and a sustainable diet, respectively, by changing theamount of any food they currently ate by up to 50 %. The majority required changes to the amount of each foodeaten plus the addition of new foods. Fewer than 5 % had to remove foods they ate to meet recommendations.Sodium proved the most difficult nutrient recommendation to meet. The healthy diets and sustainable dietsproduced a 15 and 27 % reduction in greenhouse gas emissions respectively.Conclusions: Since healthy diets alone do not produce substantial reductions in greenhouse gas emissions, dietaryguidelines need to include recommendations for environmental sustainability. Minimising the shift from currentdietary intakes is likely to make dietary change more realistic and achievabl