(P05-20-26) Does Functional Unit Choice Change Conclusions About the Environmental Sustainability of Diets? A Nutritional Life Cycle Assessment of a Pulse-Forward Pattern

Objectives:
Sustainable healthy diet interventions are of growing interest to institutions, researchers, and practitioners. However, the magnitude and directionality of environmental impacts of dietary patterns may depend on the selected functional unit (FU). We evaluated how FU affects interpretation of environmental impacts in a pulse (dry edible seeds of non-oilseed legumes, e.g., chickpeas, dry beans, lentils)-forward dietary pattern compared with an isocaloric, isonitrogenous pulse-free control.

Methods: We conducted a comparative nutritional life cycle assessment. Nutrient density was quantified using the Nutrient Rich Foods Index (NRF15.3), which includes 15 encouraged nutrients and 3 to limit. Inventory data were obtained from the ecoinvent 3.11 database; when unavailable, data were sourced from the literature and Agri-footprint version 6. Environmental impacts were estimated using the ReCiPe 2016 midpoint (H) method and included global warming potential (GWP), freshwater eutrophication and ecotoxicity, and water and land use. Impacts were expressed with two FUs: per kilogram (kg) of food and per nutrient density unit (NDU).

Results: The pulse-forward dietary pattern was more nutrient dense than the control, with nearly twice the fiber, higher B vitamin content, and lower sodium. It also had lower environmental impacts than the control for all indicators and both FUs. However, FU choice changed the magnitude of these differences. For example, the percent difference in GWP between the diets exceeded 100% per kg, but was only 46% per NDU.

Conclusions: Functional units can shape conclusions about the environmental impacts of diets. Because the primary function of food is nourishment, mass or individual nutrient-based comparisons may misrepresent environmental impacts. Incorporating multi-nutrient-based FUs is essential for advancing rigorous, nutrition-centered approaches to sustainable diet research.

Funding Sources: This work is supported by the Pulse Crop Health Initiative from the U.S. Department of Agriculture’s National Institute of Food and Agriculture.