Background:
A substantial body of epidemiological and experimental evidence indicates that nutrition influences cancer risk, but quantifying the effects of specific dietary factors and broader dietary patterns remains difficult because of exposure misclassification, confounding, and limitations in capturing long-term habitual intake. Recent advances in digital data collection and omics technologies provide opportunities to strengthen the evidence base and inform cancer prevention, including in the context of sustainability.

Objectives:
To identify key methodological challenges in research on diet and cancer and to consider how integrating dietary, lifestyle, and biomarker and genetic data may improve epidemiological evidence at the population level.

Methods:
Developments in nutritional epidemiology include improved assessment of long-term diet using repeated, web-based dietary tools, together with more extensive use of biomarkers and multi-omics data, including proteomics. Integrating dietary and molecular data allows examination of biological processes relevant to cancer and is increasingly being incorporated into both new and existing large-scale prospective studies. The potential to apply this integrative approach will be demonstrated using a new study, EPIC-Oxford 2.

Results:
Evidence shows that dietary assessment alone has limitations for characterising usual intake, which has implications for investigating diet-cancer relationships. Biomarkers of dietary intake and nutritional status add complementary information, and help improve exposure assessment, although careful validation and interpretation are required. Proteomics is a promising approach and may offer insights into underlying biological mechanisms, but substantial methodological challenges remain in analysing and interpreting integrated datasets.

Conclusions/Implications:
Further progress in research on diet and cancer will require well-designed population-based studies that combine improved assessment of long-term diet alongside complementary data to further improve our understanding. Strengthening the evidence base is essential for developing effective cancer prevention strategies, with particular relevance for addressing established diet-related risk factors at the population level.