Using nutritional functional units provides a nuanced view of the environmental performance of food products within the same category

PurposeAccording to ISO norm 14044, life cycle assessment (LCA) calculations should be based on a functional unit (FU) that is representative of a product's function. Despite this, LCAs of food products rarely deviate from a mass-based FU. This study aimed to evaluate how the use of different nutritional FUs might influence analyses of the environmental performance of food products within the same food category.MethodsDifferent FUs were used to conduct LCAs of two sets of food products: 80 industrial pizzas and 44 artisanal cheeses. For both food categories, we investigated FUs based on energy content, protein content, and a French nutritional index (SAIN). For pizza, we assessed additional FUs based on portion size, fiber content, and a combination of protein and fiber content; for cheese, we also calculated FUs for calcium content and a combination of protein and calcium content. LCAs were performed using SimaPro software. We then examined how the relative environmental performance (ranking) of the 80 pizzas and the 44 cheeses changed depending on the FU used for analysis.Results and discussionThe use of a FU based on a particular nutrient always improved the apparent environmental performance of products that were rich in that nutrient. This phenomenon was particularly pronounced in cases where a mass-based FU revealed only small variation in environmental impacts between products, when products were rich in the nutrients analyzed by the FU, and when there was a range in the nutrient content of products. Therefore, different nutritional FUs yielded different results depending on the product and the environmental indicator studied, and proper interpretation also required critical analysis of the reference flows involved. Finally, we found that products from the same category were not necessarily nutritionally similar, and that nutritional and environmental dimensions could be contradictory, meaning that both should be evaluated together.ConclusionsUsing nutritional FU can influence greatly the results when the goal is to compare different food products from the same category. Each of the nutritional FU used in this study brings out different information and could therefore be used complementary in order to get a deeper understanding of the environmental performance of the products. However, different FUs can yield contradictory results, potentially complicating interpretation by stakeholders.