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Diet & Colon Cancer Prevention


While researching the Adventists diet study for prostate cancer prevention, Al Pater kindly pointed me to a similar study [1] of diet and colon cancer risk among the Adventists in the AHS-2 study by the same authors (thanks Al!).


It followed 96,000 Adventists of both genders for an average follow-up time of 7.3 years to see which diets were associated with a reduced risk of colon cancer.  As expected, all vegetarians combined were 22% less likely than omnivores to develop any form of colon cancer during the follow-up  (HR 0.78: 95% CI, 0.64-0.95).


Here is the breakdown of colon cancer risk by various types of vegetarian diets, again relative to omnivores:

  • Vegans                        0.84 (95% CI, 0.59-1.19);
  • lacto-ovo vegetarians     0.82 (95% CI, 0.65-1.02);
  • pescovegetarians,         0.57 (95% CI, 0.40-0.82)
  • semivegetarians,           0.92 (95% CI, 0.62-1.37)

For colon cancer, it appears to be the pesky pesco-vegetarians who have the lowest risk of colon cancer.  ;)xyz


But vegans win overall, at least among this healthy Adventist population relative to all cancers (not just prostate or colon cancer), according to [2]. From the abstract:


... vegan diets showed statistically significant protection for overall
cancer incidence (HR, 0.84; 95% CI, 0.72-0.99) in both genders combined.


Here is the diagram from [2] comparing the overall cancer risk for different forms of vegetarian diets, relative to omnivores:




If we look at the male & female line (first highlight) or the male-only line (second highlight) in the fully adjusted model (including adjusting for BMI), it is only the vegan dietary pattern that reaches the level of 0.05 significance, and is P < 0.05 for the combined gender group. The other vegetarian subgroups failed to show a statistically significant lower overall risk of cancer relative to omnivores.


Go ahead - call my Dr. Greger. But thems the data...  :)xyz





[1] JAMA Intern Med. 2015 May;175(5):767-76. doi: 10.1001/jamainternmed.2015.59.

Vegetarian dietary patterns and the risk of colorectal cancers.

Orlich MJ(1), Singh PN(2), Sabaté J(1), Fan J(2), Sveen L(2), Bennett H(2),
Knutsen SF(1), Beeson WL(2), Jaceldo-Siegl K(1), Butler TL(2), Herring RP(2),
Fraser GE(1).

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.

PMCID: PMC4420687
PMID: 25751512



[2] Cancer Epidemiol Biomarkers Prev. 2013 Feb;22(2):286-94. doi:

10.1158/1055-9965.EPI-12-1060. Epub 2012 Nov 20.

Vegetarian diets and the incidence of cancer in a low-risk population.

Tantamango-Bartley Y(1), Jaceldo-Siegl K, Fan J, Fraser G.

Author information:
(1)Department of Epidemiology and Biostatistics, Loma Linda University, School of
Public Health, Loma Linda, CA 92350, USA. ytantamango@hotmail.com

BACKGROUND: Cancer is the second leading cause of death in the United States.
Dietary factors account for at least 30% of all cancers in Western countries. As
people do not consume individual foods but rather combinations of them, the
assessment of dietary patterns may offer valuable information when determining
associations between diet and cancer risk.
METHODS: We examined the association between dietary patterns (non-vegetarians,
lacto, pesco, vegan, and semi-vegetarian) and the overall cancer incidence among
69,120 participants of the Adventist Health Study-2. Cancer cases were identified
by matching to cancer registries. Cox proportional hazard regression analysis was
conducted to estimate hazard ratios, with "attained age" as the time variable.
RESULTS: A total of 2,939 incident cancer cases were identified. The multivariate
HR of overall cancer risk among vegetarians compared with non-vegetarians was
statistically significant [hr, 0.92; 95% confidence interval (CI), 0.85-0.99] for
both genders combined.
Also, a statistically significant association was found
between vegetarian diet and cancers of the gastrointestinal tract (HR, 0.76; 95%
CI, 0.63-0.90). When analyzing the association of specific vegetarian dietary
patterns, vegan diets showed statistically significant protection for overall
cancer incidence (HR, 0.84; 95% CI, 0.72-0.99) in both genders combined
and for
female-specific cancers (HR, 0.66; 95% CI, 0.47-0.92). Lacto-ovo-vegetarians
appeared to be associated with decreased risk of cancers of the gastrointestinal
system (HR, 0.75; 95% CI, 0.60-0.92).
CONCLUSION: Vegetarian diets seem to confer protection against cancer.
IMPACT: Vegan diet seems to confer lower risk for overall and female-specific
cancer than other dietary patterns. The lacto-ovo-vegetarian diets seem to confer
protection from cancers of the gastrointestinal tract.

PMCID: PMC3565018
PMID: 23169929

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 Stool Weight & Colon Cancer Risk


Dr. Greger has a good video entitled Stool Size Matter, on the inverse correlation between stool weight (an obvious proxy for dietary fiber) and colon cancer risk. 


Below is the graph of data from a study [1] of 23 populations from around the world of mean daily stool weight and colon cancer incidence per 100,000 people. As you can see, people who generate more than a pound of stool per day appear to have a risk of colon cancer close to zero. From the table below the graph, you can see there were two countries in [1] where the stool weight was over a pound per day, Malaysia and Uganda. Both of them had near zero colon cancer risk per 100,000 person-years.


By this metric, I think it is safe to say that I and many CR practitioners should definitely have a very low risk of colon cancer!


P.S. Rodney - this is the kind of interpretation of epidemiological data based on a mechanistically plausible causal theory (fiber improves gut health and reduces colon cancer risk, so higher stool weight should associate with less colon cancer) that seems like what you are looking for in your prostate cancer investigations, discussed here.







Here is the data (and the countries) used to generate the table above:





[1] Gastroenterology. 1992 Dec;103(6):1783-9.


Fecal weight, colon cancer risk, and dietary intake of nonstarch polysaccharides
(dietary fiber)

Cummings JH(1), Bingham SA, Heaton KW, Eastwood MA.

Author information:
(1)University of Cambridge, England.

Free full text: http://www.gastrojournal.org/article/0016-5085(92)91435-7/pdf

Low fecal weight and slow bowel transit time are thought to be associated with
bowel cancer risk, but few published data defining bowel habits in different
communities exist. Therefore, data on stool weight were collected from 20
populations in 12 countries to define this risk more accurately, and the
relationship between stool weight and dietary intake of nonstarch polysaccharides
(NSP) (dietary fiber) was quantified. In 220 healthy U.K. adults undertaking
careful fecal collections, median daily stool weight was 106 g/day (men, 104
g/day; women, 99 g/day; P = 0.02) and whole-gut transit time was 60 hours (men,
55 hours; women, 72 hours; P = 0.05); 17% of women, but only 1% of men, passed <
50 g stool/day. Data from other populations of the world show average stool
weight to vary from 72 to 470 g/day and to be inversely related to colon cancer
risk (r = -0.78). Meta-analysis of 11 studies in which daily fecal weight was
measured accurately in 26 groups of people (n = 206) on controlled diets of known
NSP content shows a significant correlation between fiber intake and mean daily
stool weight (r = 0.84).
 Stool weight in many Westernized populations is low
(80-120 g/day), and this is associated with increased colon cancer risk. Fecal
output is increased by dietary NSP. Diets characterized by high NSP intake
(approximately 18 g/day) are associated with stool weights of 150 g/day and
should reduce the risk of bowel cancer.

PMID: 1333426

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Excellent post (yet again), Dean! I'm going to read it, and the referenced article, carefully later, but one quick point now: I see no mention in the research paper of the Bristol Stool Scale, or any other measure of stool quality (sorry if I missed it). The data would have been tighter if the researchers (or rather, perhaps, those from whom they got their data) had controlled for stool quality: high stool weight can indeed be caused, in a particular individual (diff. from the population-based metrics they're primarily interested in, of course) by diarrhea induced by IBD, celiac disease, etc., for the simple reason that the stool contains a lot of water (Bristol scale 6-7).

In any event, I put out 500-800 g of generally 4 (sometimes leaning towards 3) poop on the Bristol Scale. So I am at very low risk of colon cancer!


Poop volume (and quality) should probably, in fact, be taken into account in a cost/benefit analysis of regular colonoscopies.



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Admin Note: Since this thread is focused on prevention of colon cancer in the first place, I've moved several posts on colon cancer screening (i.e. via colonoscopy or other procedures) from this thread to a new, consolidated one entitled COLORECTAL CANCER SCREENING started by Michael Rae. Please see that thread for the continued discussion of this important topic. --Dean

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Diet seems to have an impact at least on frequency of polyps.   http://www.upmc.com/media/NewsReleases/2015/Pages/diet-swap.aspx


"African-Americans and Africans who swapped their typical diets for just two weeks similarly exchanged their respective risks of colon cancer as reflected by alterations of their gut bacteria"


“The African-American diet, which contains more animal protein and fat, and less soluble fiber than the African diet"


"The researchers also noted they removed intestinal polyps from nine of the African-American volunteers, but none were present in the Africans."

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I have also seen one paper which found there to be a doubling of risk of colon issues for those who had had an appendectomy, but I do not recall whether the risk was for polyps or cancer.


My brother and I both had ruptured appendixes, and in both cases the polyps are in the ascending colon (immediately downstream of where the appendix was).


I have looked for, but been unable to locate, papers finding appendix rupture to be associated with an especially high risk of polyps and/or cancer.  But that may simply be because no one has thought of looking into the matter.


Anyway, the above does suggest those no longer possessing an appendix, and especially those whose appendix ruptured before removal, might be well served by being especially conscientious about this.



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