Balancing Diet Quality and Environmental Impact in Self-Selected Diets of Older Adults in Ireland

Background Shifting toward sustainable diets is a key strategy for addressing both climate change and public health challenges. However, many proposed sustainable diets rely on theoretical models that differ markedly from current eating habits and may overlook important trade-offs. This study aimed to identify self-selected eating patterns in older adults in Ireland that are both nutritionally adequate and environmentally favorable. Methods Dietary data were analysed from 1,860 free-living, older adults from a population-based cohort in the southwest of Ireland (2010–2011). Diet quality was assessed using the Mean Adequacy Ratio (MAR) and Mean Excess Ratio (MER). Environmental impact was estimated for each diet using greenhouse gas emissions (GHGE) and blue water use (BWU) indicators, based on life cycle assessment data from UK studies. Energy-adjusted multiple factor analysis, followed by hierarchical clustering identified dietary patterns with lower environmental impacts and higher nutritional quality. Results Four distinct dietary clusters were identified. One cluster, comprising 31% of the sample, had the highest micronutrient adequacy and moderate daily GHGE (6.3 kg CO₂-equivalent) and BWU (344 litres), making it the most nutritionally and environmentally balanced pattern. The cluster with the lowest environmental impact had the lowest nutritional quality. In contrast, the cluster with the highest GHGE (9.63 kg CO₂-equivalent/day) had the highest protein intake, with a greater proportion of participants meeting proposed higher protein targets important for preserving muscle mass and function. Conclusion One cluster had the highest nutritional quality and moderate environmental impacts, offering a promising compromise. While not the lowest in environmental burden, it highlights the potential to identify healthier, more sustainable diets grounded in existing eating behaviours. For older adults, dietary shifts that promote healthy ageing and advance environmental goals are more likely to succeed when grounded in realistic, culturally acceptable changes rather than idealised or prescriptive models that diverge from current practices.