Use of 24-Hour Recalls to Assess Adherence to Cancer Specific Dietary Guidelines: Experiences from the Advancing Survivorship Cancer Outcomes Trial (ASCOT)

People living with and beyond cancer (LWBC) are advised to follow World Cancer Research Fund (WCRF) dietary guidelines. However, there is no established methodology to assess adherence. This study aimed to: (i) develop methodology to process dietary recalls into a format comparable to WCRF guidelines and (ii) evaluate the impact of additional data processing on estimates of dietary intake, in people LWBC. Advancing Survivorship Cancer Outcomes Trial (ASCOT) participants completed two 24-h dietary recalls at four timepoints using myfood24. Five WCRF recommendations (limiting consumption of energy dense foods, red meat and processed meat, and increasing consumption of fruit and vegetables and wholegrains and pulses) were operationalized (e.g. ≤ 500 g red meat per week). Quality control checks indicated the need for additional processing, including changing portion sizes and choosing alternative items from myfood24 to improve accuracy. Compared to myfood24 output, the processed dietary data indicated lower intake of fruit and vegetables, and higher intake of NSP and AOAC fiber (all ps < 0.001). Developing methodology to allow assessment of 24-h dietary recall data against WCRF guidelines was possible and necessary but resource intensive. Additional data processing impacted estimates of the key foods and nutrients consumed by trial participants in a meaningful way.