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Meta-Analysis
. 2022 Jun 3:10:892153.
doi: 10.3389/fpubh.2022.892153. eCollection 2022.

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

Yujie Zhao  1 , Junyi Zhan  2 , Yongsen Wang  1 , Dongli Wang  1
Affiliations
Meta-Analysis

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

Yujie Zhao et al. Front Public Health. .

Abstract

Background and objectives: Diets 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.

Methods: We 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.

Results: The 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.

Conclusions: Plant-based diets were protective against cancers of the digestive system, with no significant differences between different types of cancer.

Systematic review registration: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022322276, Identifier: CRD42022322276.

Keywords: cancer; digestive system; eating habits; meta-analysis; plant-based diet.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Flow chart of records retrieved, screened and included in this meta-analysis.
Figure 2
Figure 2
Overall analysis of plant-based diets and cancer risk in cohort studies and case-control studies with risk ratio (RR), odds ratio (OR) and 95% confidence interval (CI). (A) Pancreas cancer with cohort study in overall analysis (adjusted). (B) Pancreas cancer with case- control study in overall analysis (adjusted). (C) Colorectal cancer with cohort study in overall analysis (adjusted). (D) Colorectal cancer with case-control study in overall analysis (adjusted). (E) Colon cancer with cohort study in overall analysis (adjusted). (F) Colon cancer with case- control study in overall analysis (adjusted). (G) Rectal cancer with cohort study in overall analysis (adjusted). (H) Rectal cancer with case-control study in overall analysis (adjusted). (I) Gastric cancer with cohort study in overall analysis (adjusted). (J) Gastric cancer with case-control study in overall analysis (adjusted). (K) esophagus cancer with cohort study in overall analysis (adjusted). (L) esophagus cancer with case- control study in overall analysis (adjusted). (M) Pharyngolaryngeal cancer with case-control study in overall analysis (adjusted). (N) Liver cancer with cohort study in overall analysis (adjusted). (O) Liver cancer with case- control study in overall analysis (adjusted).
Figure 3
Figure 3
The Begg's funnel plots for plant-based diets and cancer risk. (A), Plant-based diets and cancer risk in cohort studies. (B), Plant-based diets and cancer risk in case-control studies.
See this image and copyright information in PMC

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