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Vegetarian Dietary Pattern, Particularly Pescovegetarian Pattern, Is Associated With Reduced Risk of Colorectal Cancer

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Key Points

  • A vegetarian dietary pattern was associated with a 22% reduction in the risk for colorectal cancer.
  • A pescovegetarian dietary pattern was associated with a 43% reduction in the risk for colorectal cancer.

In a study reported by Orlich et al in JAMA Internal Medicine, a vegetarian dietary pattern was associated with a reduced risk of colorectal cancer, with risk reduction appearing to be greatest in pescovegetarians.

Study Details

The study involved data from 77,659 participants in the Adventist Health Study 2 recruited between January 2002 and December 2007. Diet, assessed at baseline, was categorized into a nonvegetarian pattern (48%) or four vegetarian patterns consisting of vegan (7.6%), lacto-ovo vegetarian (28.9%), pescovegetarian (10.0%), and semivegetarian (5.5%).

Those patients categorized as vegan consumed eggs/dairy, fish, and all other meats less than one time per month; lacto-ovo vegetarians consumed eggs or dairy one or more time per month but fish and other meats less than one time per month; pescovegetarians consumed fish one or more times per month but all other meats less than one time per month; and semivegetarians consumed nonfish meats one or more times per month but one or less time per week.

Risk Reductions

During a mean follow-up of 7.3 years, 380 cases of colon cancer and 110 cases of rectal cancer were documented. Adjusted hazard ratios for all vegetarians combined vs nonvegetarians were 0.78 (95% confidence interval [CI] = 0.64–0.95) for all colorectal cancers, 0.81 (95% CI = 0.65–1.00) for colon cancer, and 0.71 (95% CI = 0.47–1.06) for rectal cancer. Results for vegetarian vs nonvegetarian patterns were similar for men and women and for black and nonblack persons.

Adjusted HRs for all colorectal cancers were 0.84 (95% CI = 0.59–1.19) for vegans, 0.82 (95% CI = 0.65–1.02) for lacto-ovo vegetarians, 0.57 (95% CI = 0.40–0.82) for pescovegetarians, and 0.92 (95% CI = 0.62–1.37) for semivegetarians.

The investigators concluded: “Vegetarian diets are associated with an overall lower incidence of colorectal cancers. Pescovegetarians in particular have a much lower risk compared with nonvegetarians. If such associations are causal, they may be important for primary prevention of colorectal cancers.”

Michael J. Orlich, MD, PhD, of Loma Linda University, is the corresponding author of the JAMA Internal Medicine article.

The study was supported in part by the National Cancer Institute and World Cancer Research Fund. For full disclosures of the study authors, visit archinte.jamanetwork.com.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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