Dietary-Lifestyle Patterns and Colorectal Cancer Risk: Global Cancer Update Programme (CUP Global) Systematic Literature Review.

Background: While healthy dietary and lifestyle factors have been individually linked to lower colorectal cancer (CRC) risks, recommendations for whole diet-lifestyle patterns remained unestablished due to limited studies and inconsistent pattern definitions.

Objective: This updated review synthesized literature on dietary-lifestyle patterns and CRC risk/mortality.

Methods: PubMed and Embase were searched through 31 March 2023 for randomized controlled trials and prospective cohort studies examining adulthood dietary patterns combined with modifiable lifestyle factors such as adiposity, smoking, alcohol consumption, physical activity, and/or others. Patterns were categorized by derivation methods: a priori, a posteriori, and a hybrid combining both; and were then descriptively reviewed for the primary outcomes: CRC risk or mortality. The Global Cancer Update Programme Expert Committee and Expert Panel independently graded the evidence on the likelihood of causality using pre-defined grading criteria.

Results: Thirty-three observational studies were reviewed. 'Strong-probable' evidence was concluded for higher levels of alignment with the a priori-derived World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) recommendations score and lower CRC risk; and 'limited-suggestive' evidence for the American Cancer Society guidelines and Healthy Lifestyle Index with lower CRC risk (mainly due to concerns about risk of bias for confounding). A posteriori-derived patterns lack firm evidence (only one study). 'Strong-probable' evidence was concluded for higher levels of alignment with the Empirical Lifestyle Index for Hyperinsulinemia hybrid pattern and higher CRC risk. By cancer subsite, only the WCRF/AICR recommendations score showed 'strong-probable' evidence with lower colon cancer risk. All exposure-mortality pairs were graded 'limited-no conclusion'. The evidence for other pattern-outcome associations was graded as 'limited-no conclusion'.

Conclusions: Adopting a healthy pattern of diet, maintaining a healthy weight, staying physically active, and embracing health-conscious habits, such as avoiding tobacco and moderating alcohol, are collectively associated with a lower CRC risk. Healthy lifestyle habits are key to primary CRC prevention.