How stable isotopes can advance nutrition assessments to inform sustainable food systems.

Global food security challenges, driven by the need to feed an estimated 10 billion people by 2050, require sustainable agricultural practices which strengthen nutritional adequacy while minimising environmental impacts. Yet, decision-making to foster food systems which consider both human and planetary health is growing in complexity. This paper, presented at an International Atomic Energy Agency-supported symposium at the 14th European Nutrition Conference of the Federation of European Nutrition Societies, highlights the potential of stable isotope techniques in generating valuable evidence to help support the development of sustainable food systems. It focuses on three methods: the dual tracer stable isotope technique for measuring protein digestibility, the Fe isotope dilution technique for assessing Fe absorption, loss and balance and the deuterium oxide dose-to-mother technique for estimating breast milk intake. The dual tracer isotope method provides a minimally invasive assessment of protein quality from a diverse variety of crops and novel sources, supporting the transition towards environmentally conscious, protein-rich diets. The Fe isotope dilution technique can be used to address Fe requirements across different population groups and calculate Fe absorption from whole diets or after consuming crops designed to be nutritionally sufficient, thus guiding dietary guidelines and agricultural strategies. Finally, the deuterium oxide dose-to-mother technique provides precise data on breast milk intake, underscoring the role of breastfeeding in sustaining optimal infant nutrition and the conservation of resources. These methods have the ability to generate critical evidence to support policy development and food system innovations that prioritise human health and environmental preservation.