Extending the product-group-specific approach in nutritional life cycle assessment

Purpose Recent methodological developments have integrated nutritional aspects into life cycle assessment (LCA) by using nutrient indices as functional units (nFUs). Previous developments have focused on protein-rich foods, but environmental impacts and nutritional composition vary across products in other product groups, highlighting the need to develop nFUs also for other product groups. Here, we present product-group-specific nFUs for vegetables, fruit and berries, and sources of carbohydrates as an extension to our previous study on protein sources. Methods We first justified the basis of product grouping and the procedure to develop product-group-specific nutrient indices to be used as the nFU in the LCA for product groups of vegetables, fruit and berries, and sources of carbohydrates. The practical application of these indices was then tested through demonstrative LCAs for the selection of different foods. The performance and results obtained with product-group-specific nFUs, including previously developed nFU for protein sources, were evaluated through a comparison with an assessment done using a general index, which included all the nutrients with the recommended daily intake in Finnish nutrition recommendations. Results and discussion The results showed that the product-group-specific nFUs resulted in index scores that were an average of 2.5 times higher, and therefore lower climate impacts per nFU for the assessed food products, than the general index. This demonstrated that product-group-specific nFUs accurately represented the relevant nutrients for the studied product group and provided specific information on the impact of substituting currently consumed foods. The relative results obtained with either product-group-specific indices or a general index were similar except in the protein source product group, showing that a product-group-specific nFU might favour a certain type of products, such as traditional protein source foods, when applied to a very heterogenous group of products. Conclusions This study showed that the product-group-specific approach could provide valuable information when evaluating the sustainability of different meal components. The approach presented here can be adapted elsewhere and revised for different populations. However, future research is needed to extend the method to cover other product groups as well and validate the selection of nutrients in the nFUs.