A new review maps the growing toolbox used to judge meals and diets on both nutrition and environmental impact, but shows that inconsistent methods still stand in the way of a clear standard.
Food-based indices for the assessment of nutritive value and environmental impact of meals and diets: A systematic review. Image Credit: PeopleImages / Shutterstock
In a recent study published in the journal PLOS ONE, researchers examined food-based indices that classify or rank meals and diets based on environmental impact and nutritive value.
Food labeling is widely used to influence consumption practices by providing consumers with product information. While nutrition labeling is mandatory and regulated in the United Kingdom (UK), there has been substantial interest in integrating sustainability information into labeling. This reflects increasing awareness of the food system's role in resource depletion, climate change, and biodiversity loss.
Sustainability is a broad concept with multiple dimensions, including cultural acceptability and affordability, which may lead to inconsistencies in application. Focusing specifically on environmental impact and nutritional value may help reduce consumer misperceptions and improve understanding of environmentally responsible and healthy dietary choices.
About the study
In this study, researchers investigated food-based indices that assess environmental impact and nutritive value to classify or rank diets and meals. These indices were termed nutritive and environmental combined indices (NECIs).
Six bibliographic databases were searched for relevant original studies published between January 2009 and August 2025. Reviews were excluded, although their reference lists were screened for additional studies.
Eligible studies assessed both the environmental impact and the nutritional value of diets or meals. Studies focusing on only one aspect or on individual foods were excluded. Broader sustainability dimensions, including sociocultural and economic factors, were also considered.
Relevant data, including study characteristics, methodological details, and public health purposes, were extracted. Replicability was used as a quality assessment metric, defined as the transparency and reproducibility of an NECI’s methodology. The review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines and was conducted by two independent reviewers. The protocol was registered in the International Prospective Register of Systematic Reviews (PROSPERO).
Findings
Database searches identified 13,634 records, and an additional 9 were identified through reference screening. After deduplication and screening, 25 studies describing 27 methodological approaches for 25 NECIs were included.
Two studies presented a single index with two scoring methods, whereas others presented a single index. Nine NECIs were designed for diets, six for meals, and 10 for both.
Twelve NECIs incorporated additional sustainability dimensions beyond environmental impact and nutrition, most commonly economic and sociocultural factors. Fifteen NECIs were developed by individual institutions, while 10 were developed through collaborations, primarily involving universities and research institutions.
Most NECIs (24) targeted adults, and one addressed the general population. Seventeen were developed for European populations. Nutritional scoring commonly uses variations of the Nutrient Rich Diet score, typically calculated based on mass, though some use energy-based metrics.
Nutritional scoring relied on individual nutrients in most approaches, with fewer using food groups or combined methods. Life cycle assessment was the most common approach for environmental scoring, typically based on food quantity.
Substantial variation was observed in scoring methods, functional units, system boundaries, weighting approaches, ranking criteria, and presentation formats. Some NECIs used a single integrated score, whereas others presented environmental and nutritional scores separately, limiting direct comparability.
Twenty-one NECIs were considered replicable, one possibly replicable, and one non-replicable. Key public health applications included policy development, research, decision support, dietary guideline development, and consumer education.
Conclusions
The study identified 25 indices that assess both the environmental impact and the nutritive value of diets and meals. Findings highlight considerable methodological heterogeneity across NECIs, underscoring the need for harmonized criteria.
Standardization of these indices may support more consistent comparisons and improve their utility for public health decision-making, ultimately helping promote environmentally sustainable and healthy dietary choices.
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