Dietary patterns and risk of multiple cancers: umbrella review of meta-analyses of prospective cohort studies.

Background: Numerous prospective cohort studies have investigated the influence of dietary patterns on the risks of various cancers, although the findings differed.

Objectives: To evaluate the associations of dietary patterns with risks of various cancers and assess the strength and validity of the evidence.

Methods: Relevant articles were retrieved from the PubMed, EMBASE, Web of Science, and Cochrane library databases from inception to February 22, 2024. The included systematic reviews were meta-analyses of prospective cohort studies that reported an effect size to calculate the association between dietary patterns and cancer risk. The quality of the included studies was evaluated using a measurement tool to assess systematic reviews and the certainty of evidence was assessed using credibility assessment of evidence. Outcomes of interest included any incident cancers. This study was registered with PROSPERO (CRD42023425237).

Results: Overall, 74 meta-analyses from 30 articles were identified. Three meta-analyses (4.1%) were graded as convincing evidence and included associations between adherence to the 2007 World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) dietary recommendations (per 1-unit score increase) and lower risk of all cancers (relative risk [RR] = 0.93, 95% confidence interval [CI]: 0.92, 0.95), whereas negative associations were found comparing the highest compared with lowest categories for a prudent diet (RR = 0.89, 95% CI: 0.85, 0.93) and vegetable-fruit-soybean diet (RR = 0.87, 95% CI: 0.83, 0.92) in relation to breast cancer. After credibility assessment of evidence by Grading of Recommendations, Assessment, Development, and Evaluation, 4 (5.4%) meta-analyses were classified as high, including adherence to the 2007 WCRF/AICR dietary recommendations and decreased risks of all cancers, breast cancer, colorectal cancer, and prostate cancer.

Conclusions: These findings suggest that adherence to certain healthy dietary patterns is associated with lower risk of all cancers and certain individual cancers. This study was registered at crd.york.ac.uk, PROSPERO as CRD42023425237 and /PROSPERO/display_record.php?RecordID=425237.