March 30, 2015
JAMA Internal Medicine
TAKE-HOME MESSAGE
In the Adventist Health Study 2, including 96,354 Seventh-Day Adventist men and women, those following a vegetarian diet had a lower incidence of colorectal cancers than nonvegetarians (HR, 0.78). The effect was most pronounced in pescovegetarians.
Results suggest that a vegetarian lifestyle may be important for colorectal cancer primary prevention.
Primary Care
Written by David Rakel MD, FAAFP
What is a Pesco Vegetarian?
Pesco, meaning fish in Italian, is a vegetarian that eats fish. But although this group had the lowest incidence of colon cancer, there is more to it. The authors of this study evaluated over 96,000 Seventh Day Adventists in North America, a very healthy group with the most centenarians on this side of the Pacific. They generally eat well, do not smoke, do not drink, and are part of a spiritual community. The homogeneity of this study strengthens it and helps explain why this group already has a 27% reduced risk of colon cancer (CC) compared with the rest of us mortals.
The researchers divided this community into the following groups.
Vegetarians: No eggs, dairy, fish, or meat
Lacto-ovo vegetarians: Eat dairy and eggs, but no meat
Pesco-vegetarian: Eat fish
Semi-vegetarians: Eat fish and meat in small amounts
Non-vegetarians: Eat more meat
To put this population into perspective, the authors note that the non-vegetarian meat eaters in this study still ate less meat than the lowest quartile of meat eaters in other large studies looking at CC risk in general populations.
Within this healthy community, the reduction of CC in vegetarians vs non-vegetarians was 20%. This number jumped to 42% for pesco-vegetarians. It is possible that the anti-inflammatory effects of the omega-3 fatty acids in fish had a benefit but this is speculative. Comparing risk reduction to non-Seventh Day Adventist populations would likely be greater.
The reduced risk may have not only been related to not eating meat (previous research shows processed meat to be the worst), but from eating more fibrous vegetables and fruit. You can be a vegetarian and NOT eat well. Some substitute high carb “white foods” instead of vegetation, but not in this group. The Seventh Day Adventists ate high amounts of vegetables and fruit.
If you want to live to be 100 years old and cut your risk from the second-leading cause of cancer death by 42% (or more), eat vegetation with fish, do not smoke, limit alcohol, and be a part of a social spiritual community!
Abstract
IMPORTANCE
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.
DESIGN, SETTING, AND PARTICIPANTS
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.
EXPOSURES
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.
MAIN OUTCOMES AND MEASURES
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 AND RELEVANCE
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.