What happens when nutrition research moves beyond asking whether an intervention works and starts examining why it works, for whom and under which conditions?

Alejandro is joined by Saffron Whyton, a PhD researcher at the University of Surrey whose work sits at the intersection of nutrition and psychology, with a particular focus on plant-based diets, healthy ageing and care homes.

Drawing on her realist synthesis, Saffron explores a challenge familiar across nutrition and public health research: conventional evidence reviews can tell us whether anintervention appears to work, but they often give less attention to the social context and underlying mechanisms that shape whether people can or will change what they eat. These questions become especially important in care homes, where settings and resident needs vary considerably.

The conversation explores how realist approaches can support the design of plant-based meal interventions that are both evidence-informed and sensitive to context. Saffron discusses person-centred care, theoretical transferabilitywhen direct evidence is limited, the use of substantive theory and the value of combining qualitative and quantitative evidence to develop and refine initial programme theories.

But applying realist approaches in nutrition also brings challenges. Alejandro and Saffron discuss sparse reporting of contexts and mechanisms, the technical language surrounding realist methods, the shift from a predominantly positivist background, and the importance of being transparent about limitations while treating programme theories as iterative and open to refinement.

Whether you are a realist evaluator, realist reviewer, nutrition researcher, dietitian, public health researcher, care-home practitioner, student, supervisor, or PhD researcher, this episode offers an accessible exploration of how realistthinking can produce more useful explanations of dietary change and more practical recommendations for policy and practice