The Relationship Between Plant-Based Diet and Risk of Digestive System Cancers: A Meta-Analysis Based on 3,059,009 Subjects

Abstract

Background and ObjectivesDiets containing red or processed meat are associated with a growing risk of digestive system cancers. Whether a plant-based diet is protective against cancer needs a high level of statistical evidence.MethodsWe performed a meta-analysis of five English databases, including PubMed, Medline, Embase, Web of Science databases, and Scopus, on October 24, 2021 to identify published papers. Cohort studies or case-control studies that reported a relationship between plant-based diets and cancers of the digestive system were included. Summary effect-size estimates are expressed as Risk ratios (RRs) or Odds ratios (ORs) with 95% confidence intervals and were evaluated using random-effect models. The inconsistency index (I2) and τ2 (Tau2) index were used to quantify the magnitude of heterogeneity derived from the random-effects Mantel-Haenszel model.ResultsThe same results were found in cohort (adjusted RR = 0.82, 95% CI: 0.78–0.86, P < 0.001, I2 = 46.4%, Tau2 = 0.017) and case-control (adjusted OR = 0.70, 95% CI: 0.64–0.77, P < 0.001, I2 = 83.8%, Tau2 = 0.160) studies. The overall analysis concluded that plant-based diets played a protective role in the risk of digestive system neoplasms. Subgroup analyses demonstrated that the plant-based diets reduced the risk of cancers, especially pancreatic (adjusted RR = 0.71, 95% CI: 0.59–0.86, P < 0.001, I2 = 55.1%, Tau2 = 0.028), colorectal (adjusted RR = 0.76, 95% CI: 0.69–0.83, P < 0.001, I2 = 53.4%, Tau2 = 0.023), rectal (adjusted RR = 0.84, 95% CI: 0.78–0.91, P < 0.001, I2 = 1.6%, Tau2 = 0.005) and colon (adjusted RR = 0.88, 95% CI: 0.82–0.95, P < 0.001, I2 = 0.0%, Tau2 = 0.000) cancers, in cohort studies. The correlation between vegan and other plant-based diets was compared using Z-tests, and the results showed no difference.ConclusionsPlant-based diets were protective against cancers of the digestive system, with no significant differences between different types of cancer.Systematic Review Registrationhttps://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022322276, Identifier: CRD42022322276.

Diets, Dietary Patterns, Single Foods and Pancreatic Cancer Risk: An Umbrella Review of Meta-Analyses

“…The reasons for exclusion are shown in Supplementary Table S2 . At the end of the screening process, 23 articles met the inclusion criteria and were included in the current review [ 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 ]. All the included systematic reviews and meta-analyses only included original observational studies (case-control and/or cohort studies).…”

“…All the included articles were meta-analyses of observational studies (case-controls or cohort studies). Among the 23 articles included, 7 were studies assessing the association between dietary patterns and PC risk [ 35 , 39 , 40 , 43 , 48 , 52 , 56 ], whereas the remaining 16 studies analyzed the association between one or more dietary components and the risk of PC [ 36 , 37 , 38 , 41 , 42 , 44 , 45 , 46 , 47 , 49 , 50 , 51 , 53 , 54 , 55 , 57 ]. However, out of the 23 included articles, a total of 13 unique meta-analyses on dietary patterns and 29 unique meta-analyses on dietary components were detected because the articles reported the summary effect size separately by sex or study design.…”

“…The oldest article retrieved was published in 1998 and assessed the association between whole grain and PC risk [ 42 ]. The two newest meta-analyses were published in 2022: one assessed two dietary components (poultry and fish) [ 38 ], and the other one assessed the association between plant-based diets and the risk of PC [ 56 ]. In all meta-analyses except one [ 41 ], authors compared the highest vs lowest dietary pattern adherence or diet component intake.…”

Vegetarian and Vegan Diets: Beliefs and Attitudes of General Practitioners and Pediatricians in France

“…A protective effect of the vegetarian diets was found on blood pressure as well as on type 2 diabetes and obesity, even in childhood [ 7 , 8 , 9 , 10 , 11 , 12 ]. Regarding cancer, the results of studies are inconsistent, except for the consumption of red meat (especially of processed meat), which is associated with an increased risk of cancer (especially colorectal and stomach) [ 13 , 14 , 15 ]. For stroke, myocardial infarction, and overall mortality, the results are inconsistent [ 16 , 17 , 18 ].…”

Flavonoid Intake in Relation to Colorectal Cancer Risk and Blood Bacterial DNA

“…In our population, anthocyanidins mainly came from the consumption of red fruits and wine, and flavanones from citrus fruit. Adjustment for fruit and vegetable consumption did not materially change the association we found between flavonoids and CRC, suggesting that these subclasses of flavonoids can explain, at least in part, the protective effects of a diet rich in plant foods on this cancer [ 38 , 39 ].…”