The goal of activities and processes at the science-policy interface (SPI) is to improve the outcome of decision- and policy-making. The underlying rationale is that decisions and policies will be more robust and effective if they are informed by scientific evidence. The pressing challenges that humanity is facing are complex and can only be addressed by integrating across academic disciplines and by incorporating the knowledge, experience and expertise of non-academic actors. This is illustrated for the development of pathways for sustainable food systems, specifically in the context of Switzerland. Inter- and transdisciplinarity (ITD) provide valuable insights, methods, and approaches for SPI activities. Co-production of knowledge is a central ITD concept, which could be extended to co-production of policy. At the same time, the involvement of unelected experts in policy development can compromise democratic legitimacy, posing a challenge to the ITD approach.