Purpose While nutritional life cycle assessment (n-LCA) aims to integrate health and environmental sustainability, the compatibility of underlying data and methodological choices remains unclear. So, this study critically evaluates whether nutritional and environmental dimensions are methodologically adequate and aligned in n-LCAs. We assessed the consistency of functional units, system boundaries, data sources, geographic representativeness, and characterization methods to identify key misalignments and provide recommendations to improve robustness, comparability, and policy relevance. Methods A narrative scoping review was conducted on peer-reviewed n-LCA studies published between 2014 and June 2024. Articles were identified through reference mining, snowballing of prior reviews, and searches in PubMed and Scopus. Data extraction covered general characteristics, environmental assessment features (functional units, system boundaries, life cycle inventory sources, impact categories, characterization methods), and nutritional assessment features (nutritional indicators, food composition databases, preparation stage). Methodological alignment was qualitatively evaluated across three domains: (i) consistency between study context and environmental assessment, (ii) consistency between study context and nutritional assessment, and (iii) cross-dimensional compatibility. Alignment was categorized as full, partial, or absent based on predefined criteria. Results and discussion Twenty-three studies met inclusion criteria. Substantial methodological heterogeneity was observed. Mass-based functional units predominated, though energy- and nutrient-based units are increasing. Many studies relied on heterogeneous or poorly documented environmental datasets, often without transparent characterization methods. Climate change was assessed in all studies, whereas other impact categories were inconsistently reported. Nutritional assessments frequently used national food composition databases, yet 35% were partially or fully geographically misaligned. Crossdimensional inconsistencies were common, particularly regarding system boundaries (e.g., farm-gate environmental data versus ready-to-eat nutritional data), product scope, and geographic representativeness. These structural mismatches limit comparability, increase uncertainty, and risk misleading conclusions about health–environment synergies or trade-offs. Conclusions Although n-LCA holds strong potential to inform sustainable diet transitions, current practice remains fragmented due to methodological misalignments across study context, and the nutritional and environmental dimensions. Improved transparency, geographically coherent data, harmonized scope, and integration of health-outcome metrics are essential to enhance validity and policy relevance.