The SHED Index: a tool for assessing a Sustainable HEalthy Diet

Purpose: Promoting sustainable diets through sustainable food choices is essential for achieving the sustainable development goals set by the United Nations. Establishing a practical tool that can measure and score sustainable and healthy eating is highly important. Methods: We established a 30-item questionnaire to evaluate sustainable-dietary consumption. Based on the literature and a multidisciplinary advisory panel, the questionnaire was computed by principal component analysis, yielding the Sustainable-HEalthy-Diet (SHED) Index. A rigorous multi-stage process included validation in training-verification sets, across recycling efforts, as an indicator of environmental commitment; and validation across the proportion of animal-protein consumption, as an indicator of adherence to a sustainable and healthy dietary-pattern. The EAT-Lancet reference-diet and the Mediterranean-Diet-score were used to investigate the construct validity of the SHED Index score. Reliability was assessed with a test–retest sample. Results: Three-hundred-forty-eight men and women, aged 20–45 years, completed both the SHED Index questionnaire and a validated Food-Frequency-Questionnaire. Increased dietary animal-protein intake was associated with a lower SHED Index total score (p < 0.001). Higher recycling efforts were associated with a higher total SHED Index score (p < 0.001). A linear correlation was found between the SHED Index score and food-groups of the Eat-Lancet-reference diet. A significant correlation was found between the Mediterranean-Diet-score and the SHED Index score (r = 0.575, p < 0.001). The SHED Index score revealed high reliability in test–retest, high validity in training and verification sets, and internal consistency. Conclusion: We developed the SHED Index score, a simple, practical tool, for measuring healthy and sustainable individual-diets. The score reflects the nutritional, environmental and sociocultural aspects of sustainable diets; and provides a tangible tool to be used in intervention studies and in daily practice.