There is growing international consensus that current patterns of food consumption are not sustainable and global change is needed. Understanding the mechanisms for a transition towards more sustainable diets requires systematic temporal monitoring at the individual or household level. Whilst many countries collect panel data on food expenditure and dietary intake, these datasets are often not designed to monitor progress towards dietary sustainability, therefore using them to understand how or why diets are becoming more or less sustainable can prove challenging. What is also lacking is a curated dataset catalogue or a library where all relevant data could be easily accessible to enable such evaluation. Our aim was to identify, classify and describe existing food expenditure and diet datasets available in the UK and to assess the extent to which they can be used to monitor transitions to sustainable diets. We found that despite the large number of datasets tracking UK individual or household food purchases and consumption over time, these datasets are not suited to understand how and why individuals are transitioning to sustainable diets. With the exception of proprietary datasets, most datasets only collect data annually, making it challenging to understand fine-scale behavioural change over shorter timeframes. There is an opportunity to design and implement an open-access UK sustainable diets data collection effort at the individual and household level. These efforts can be complemented with recent innovations in data science methods and digital technologies – such as dietary intake trackers – that, along with supporting individuals in their dietary behaviour change, may enable the collection of high-quality datasets.