Sustainability of Diets Consumed by UK Adolescents and Associations Between Diet Sustainability and Meeting Nutritional Requirements

<b>Background/Objectives</b>: The EAT-Lancet Commission proposed a healthy and sustainable 'planetary health diet' (PHD) based on the nutritional needs of adults, but recommended for all population groups over the age of two years. This study investigated the extent to which UK adolescent diets meet these recommendations, and the association between meeting recommendations and nutritional intake. <b>Methods</b>: Dietary intake data collected from students aged 11-15 years between 2019 and 2022 as part of the Food provision, cUlture and Environment in secondary schooLs (FUEL) study was used. Specifically, 24 h intakes of food groups and key nutrients were summarised for each participant, and micronutrient intake was expressed as a percentage of the reference nutrient intake (RNI). The proportion of participants meeting each PHD recommendation was calculated. A PHD index score was developed to measure the overall adherence to recommendations. Multilevel linear regression models were fitted to explore the association between the PHD score and intake of each nutrient. <b>Results</b>: No participants fully met the recommendations. The mean PHD score was 14.2 (3.3) out of 39. Adherence was low for the emphasised foods, and lowest for nuts (1.3%) and unsaturated oils (0.2%). Higher PHD index scores were associated with lower intakes of all micronutrients, with the largest association for vitamin B12 [regression coefficient: -12.9% (95% CI: -16.3, -9.4) of RNI] and the smallest for vitamin D [regression coefficient: -0.4 (95% CI: -0.7, -0.2) of RNI]. <b>Conclusions</b>: Substantial dietary changes are needed for this population group to meet the PHD guidelines. Further research should focus on why these recommendations may lead to the inadequate intake of some nutrients in this age group. We propose that the PHD guidance needs to be reviewed and potentially adapted for this specific population, with consideration of the typical dietary behaviours of this age group.