Can we estimate the impact of small targeted dietary changes on human health and environmental sustainability?

A recent analysis by Stylianou et al. (2021) estimated the impact of small dietary changes in the consumption of individual foods on human health and the environment, expressed as minutes of healthy life lost or gained daily combined with dietary carbon footprints. While an appealing concept given its simplistic interpretation, we aim to draw the attention of nLCA practitioners and developers to the significant limitations and uncertainties of this analysis, based on existing evidence. Stylianou's approach produces results that fail to recognize the importance of essential nutrient density and the risks associated with ultra-processed foods, added sugar, and refined starches. The novel impact assessment undoubtedly brings a new perspective to the growing field of nutritional Life Cycle Assessment. However, the authors neglect numerous methodological limitations, fail to direct the readers' attention to (mis)interpretation risks, and draw highly definitive recommendations aiming to directly influence consumer choices and policymaking. Due to extensive data limitations and associated uncertainties in extant databases (both environmental and nutritional), we recommend caution in the use of this (or any other) food classification system to inform consumer behavior, front-of-package labelling, policies, and programs.