Vegetarian dietary patterns and the risk of colorectal cancers.
OBJECTIVE
Colorectal cancers are a leading cause of cancer mortality, and their primary prevention by diet is highly desirable. The relationship of vegetarian dietary patterns to colorectal cancer risk is not well established.


OBJECTIVE
To evaluate the association between vegetarian dietary patterns and incident colorectal cancers.


METHODS
The Adventist Health Study 2 (AHS-2) is a large, prospective, North American cohort trial including 96,354 Seventh-Day Adventist men and women recruited between January 1, 2002, and December 31, 2007. Follow-up varied by state and was indicated by the cancer registry linkage dates. Of these participants, an analytic sample of 77,659 remained after exclusions. Analysis was conducted using Cox proportional hazards regression, controlling for important demographic and lifestyle confounders. The analysis was conducted between June 1, 2014, and October 20, 2014.


METHODS
Diet was assessed at baseline by a validated quantitative food frequency questionnaire and categorized into 4 vegetarian dietary patterns (vegan, lacto-ovo vegetarian, pescovegetarian, and semivegetarian) and a nonvegetarian dietary pattern.


METHODS
The relationship between dietary patterns and incident cancers of the colon and rectum; colorectal cancer cases were identified primarily by state cancer registry linkages.


RESULTS
During a mean follow-up of 7.3 years, 380 cases of colon cancer and 110 cases of rectal cancer were documented. The adjusted hazard ratios (HRs) in all vegetarians combined vs nonvegetarians were 0.78 (95% 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. The adjusted HR for colorectal cancer in vegans was 0.84 (95% CI, 0.59-1.19); in lacto-ovo vegetarians, 0.82 (95% CI, 0.65-1.02); in pescovegetarians, 0.57 (95% CI, 0.40-0.82); and in semivegetarians, 0.92 (95% CI, 0.62-1.37) compared with nonvegetarians. Effect estimates were similar for men and women and for black and nonblack individuals.


CONCLUSIONS
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.
School of Public Health, Loma Linda University, Loma Linda, California2School of Medicine, Loma Linda University, Loma Linda, California.
Michael J
MJ
Orlich
School of Public Health, Loma Linda University, Loma Linda, California.
Pramil N
PN
Singh
School of Public Health, Loma Linda University, Loma Linda, California2School of Medicine, Loma Linda University, Loma Linda, California.
Joan
J
Sabaté
School of Public Health, Loma Linda University, Loma Linda, California.
Jing
J
Fan
School of Public Health, Loma Linda University, Loma Linda, California.
Lars
L
Sveen
School of Public Health, Loma Linda University, Loma Linda, California.
Hannelore
H
Bennett
School of Public Health, Loma Linda University, Loma Linda, California2School of Medicine, Loma Linda University, Loma Linda, California.
Synnove F
SF
Knutsen
School of Public Health, Loma Linda University, Loma Linda, California.
W Lawrence
WL
Beeson
School of Public Health, Loma Linda University, Loma Linda, California2School of Medicine, Loma Linda University, Loma Linda, California.
Karen
K
Jaceldo-Siegl
School of Public Health, Loma Linda University, Loma Linda, California.
Terry L
TL
Butler
School of Public Health, Loma Linda University, Loma Linda, California.
R Patti
RP
Herring
School of Public Health, Loma Linda University, Loma Linda, California2School of Medicine, Loma Linda University, Loma Linda, California.
Gary E
GE
Fraser
D000328:Adult; D000368:Aged; D015331:Cohort Studies; D015179:Colorectal Neoplasms / Q000401:mortality / Q000517:prevention & control / Q000523:psychology; D014676:Diet, Vegetarian / Q000523:psychology*; D005247:Feeding Behavior; D005260:Female; D006801:Humans; D015994:Incidence; D008019:Life Style; D008297:Male; D008875:Middle Aged; D009026:Mortality; D011446:Prospective Studies; D012042:Registries / Q000706:statistics & numerical data; D012306:Risk; D011795:Surveys and Questionnaires; D014481:United States / Q000453:epidemiology