Discretionary foods have notable environmental and expenditure relevance across meat and plant protein preferences.

Real-world data help clarify the contribution of food to nutrition, the environment, and food expenditure. We studied the implications of a hypothetical transition in protein sources for these sustainability dimensions using loyalty-card holders' (n = 22,901) food purchases. Six consumer clusters were identified via sequence analysis, representing realistic transitions in protein sources alongside other food consumption changes. Cross-sectional comparisons revealed that higher expenditure of Plant-based and Fish clusters per 2500 kcal was largely driven by other food groups than the protein sources, while the protein source expenditure was relatively consistent across clusters. Environmental impact differences were largely attributable to the protein sources, with meat and fish contributing the most. Aside from protein sources, discretionary foods accounted for 22% of spending and contributed up to 17-32% of environmental impacts. Therefore, alongside protein source changes, reducing discretionary food consumption could yield notable environmental benefits and allow reallocation of expenditure towards more nutritious foods.