26 Jul The SHED Index: how broad should dietary assessment be to really understand sustainability?
A sustainable diet is defined as a diet that improves health, minimises the environmental impact, and is economically accessible and culturally acceptable. With the various interpretations of what a sustainable diet looks like from day to day, a recent paper proposed that this international goal would benefit from a valid and reliable index as an essential tool for its evaluation.
The evaluation of healthy diets has been well studied, but it has only more recently been combined with environmental sustainability aspects. Assessment methods for sustainable diets can require various sources of information that are not always accessible to consumers or nutrition practitioners. Also, many indicators, such as food waste, are omitted in the majority of these approaches, as are the broader dimensions of sustainability, such as socio-cultural and economic.
This research team set out to establish a practical assessment tool, including indicators as diverse as recycling efforts and the ratio of animal-to-plant protein consumption to both measure and score sustainable and healthy eating patterns, reflecting the nutritional, environmental, and socio-cultural aspects of individual diets.
Agreement of participants with statements asked as part of the SHED assessment, which ultimately combine to give a SHED index score for their diet.
In trialling their index, the authors recruited 348 people to complete the questionnaire. Higher scores correlated strongly with existing metrics for healthy diets.
The authors acknowledge that the study has some limitations; for example, the index does not quantify greenhouse gas emissions. Moreover, the results were self-reported, and therefore subject to the same challenges as food frequency questionnaires. Finally, the questions asked, although already diverse (see figure), cover only a subset of the aspects that need to be considered when assessing health and sustainability.
The SHED Index score brings together nutritional and environmental information about dietary behaviour that may be useful in intervention studies. However, as we look into the future of sustainable nutrition, the integration of health and sustainability measures into one composite score could become commonplace. We must ask to what extent such measures inform our decision making, and to what extent they reduce the information available in favour of simplicity.