Comprehensive assessment frameworks are required to measure both environmental effect (carbon footprint, greenhouse gas (GHG) emissions) and nutritional efficacy of foods. Nutritional Life Cycle Assessment (nLCA) is an imperative tool of assessment framework. The objective of this review was the synthesis of global nLCA literature to assess the existing methodologies and standards, the various tools utilized, and the outcome measures implemented to evaluate the environmental impact of various raw and packaged food products. We conducted a narrative review to synthesize the key findings from nLCA studies published between 2016 to 2020 using the PubMed database. The comparative reliability of nLCA was undermined by widespread methodological variations. The functional unit (FU) significantly determines ranking, which acts as a key and frequently contradictory conclusion. Reliance on FUs based on mass sometimes renders comparisons useless by neglecting to take nutrient profiling into account. Nutritional FUs show that products such as pulses, microbial proteins, and some intensive livestock systems can offer high nutrient delivery for a lower environmental burden, while beef and dairy consistently register as environmental hotspots. The high heterogeneity resulting from co-product allocation strategies and localized production efficiency (example: precision nutrition) was a major limitation to drawing broadly applicable findings. The nLCA community needs to get an agreement on globally standardized, nutritionally weighted FUs, prioritizing the development of public-health focused indicators such as the HENI score. Furthermore, systematic integration of social and economic factors into LCSA is required for converting complex data into holistic, region-specific actions.

Keywords:Nutritional life cycle assessment; Life cycle assessment; greenhouse gases; carbon footprint