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The Association Between Diet and Colorectal Cancer Risk: Moving Beyond Generalizations

2017; Elsevier BV; Volume: 152; Issue: 8 Linguagem: Inglês

10.1053/j.gastro.2017.04.025

1528-0012

Alan C. Moss, Kumanan Nalankilli,

Gastric Cancer Management and Outcomes

See "Dietary patterns and risk of colorectal cancer: analysis by tumor location and molecular subtypes," by Mehta RS, Song M, Nishihara R, et al, on page 1944. See "Dietary patterns and risk of colorectal cancer: analysis by tumor location and molecular subtypes," by Mehta RS, Song M, Nishihara R, et al, on page 1944. "Thank you for removing those polyps during the colonoscopy today. If I change my diet, can I reduce the risk of developing more polyps or colon cancer in the future?" This is one of the most commonly posed questions by our patients, after being informed of the outcome of their colonoscopy. It is admittedly tempting to answer somewhat flippantly that they will be returning for surveillance colonoscopies in the years to come, so they should take advantage of this and enjoy an unrestricted diet in the interim! However, recent data on the relationship between diet and colorectal cancer (CRC) risk, combined with the knowledge that colonoscopy is certainly not completely protective against CRC,1Baxter N.N. Goldwasser M.A. Paszat L.F. et al.Association of colonoscopy and death from colorectal cancer.Ann Intern Med. 2009; 150: 1-8Crossref PubMed Scopus (1063) Google Scholar increasingly supports the need to answer our patients with a considered, scientifically valid and practical response. In this edition of Gastroenterology, the article entitled, "Dietary Patterns and Risk of Colorectal Cancer: Analysis by Tumor Location and Molecular Subtypes" by Mehta et al2Mehta R.S. Song M. Nishihara R. et al.Dietary patterns and risk of colorectal cancer: analysis by tumor location and molecular subtypes.Gastroenterology. 2017; 152: 1944-1953Abstract Full Text Full Text PDF PubMed Scopus (82) Google Scholar helps us to move beyond generalizations about Western diet and CRC risk, to a more detailed understanding of the association between diet and colorectal tumor location and also molecular subtypes. Studies that examined dietary factors and various cancers showed that one of the strongest associations is between CRC and meat consumption.3Willett W.C. Diet and cancer: an evolving picture.JAMA. 2005; 293: 233-234Crossref PubMed Scopus (112) Google Scholar Recently, global publicity was generated by the World Health Organization International Agency for Research on Cancer consensus statement regarding the increased risk of CRC with consumption of processed or red meat.4Bouvard V. Loomis D. Guyton K.Z. et al.International Agency for Research on Cancer Monograph Working GCarcinogenicity of consumption of red and processed meat.Lancet Oncol. 2015; 16: 1599-1600Abstract Full Text Full Text PDF PubMed Scopus (1049) Google Scholar The 2015 statement notes that processed meat is carcinogenic to humans and lists processed meat as a group 1 substance. Processed meats result from salting, smoking, fermenting, or curing the meat, and common examples include ham, bacon, and sausage.5Chan D.S. Lau R. Aune D. et al.Red and processed meat and colorectal cancer incidence: meta-analysis of prospective studies.PLoS One. 2011; 6: e20456Crossref PubMed Scopus (590) Google Scholar Furthermore, red meat was declared as probably carcinogenic to humans, and red meat was listed as a group 2A substance.4Bouvard V. Loomis D. Guyton K.Z. et al.International Agency for Research on Cancer Monograph Working GCarcinogenicity of consumption of red and processed meat.Lancet Oncol. 2015; 16: 1599-1600Abstract Full Text Full Text PDF PubMed Scopus (1049) Google Scholar Red and processed meats are considered significant components of a "Western" diet. Other consumed substances that are associated with an increased risk of CRC include alcohol6Fedirko V. Tramacere I. Bagnardi V. et al.Alcohol drinking and colorectal cancer risk: an overall and dose-response meta-analysis of published studies.Ann Oncol. 2011; 22: 1958-1972Abstract Full Text Full Text PDF PubMed Scopus (432) Google Scholar and tobacco.7Botteri E. Iodice S. Bagnardi V. et al.Smoking and colorectal cancer: a meta-analysis.JAMA. 2008; 300: 2765-2778Crossref PubMed Scopus (572) Google Scholar In this issue of Gastroenterology, Mehta et al2Mehta R.S. Song M. Nishihara R. et al.Dietary patterns and risk of colorectal cancer: analysis by tumor location and molecular subtypes.Gastroenterology. 2017; 152: 1944-1953Abstract Full Text Full Text PDF PubMed Scopus (82) Google Scholar examine the effect of exposure to "Western" and "prudent" dietary patterns on the incidence of CRC, using multivariable Cox proportional hazards models.2Mehta R.S. Song M. Nishihara R. et al.Dietary patterns and risk of colorectal cancer: analysis by tumor location and molecular subtypes.Gastroenterology. 2017; 152: 1944-1953Abstract Full Text Full Text PDF PubMed Scopus (82) Google Scholar Data were analyzed from 2 large, ongoing, prospective cohorts with >90% follow-up rates: the Health Professionals Follow-up Study8Giovannucci E. Rimm E.B. Stampfer M.J. et al.Aspirin use and the risk for colorectal cancer and adenoma in male health professionals.Ann Intern Med. 1994; 121: 241-246Crossref PubMed Scopus (736) Google Scholar and the Nurses' Health Study,9Giovannucci E. Egan K.M. Hunter D.J. et al.Aspirin and the risk of colorectal cancer in women.N Engl J Med. 1995; 333: 609-614Crossref PubMed Scopus (979) Google Scholar where information on lifestyle and dietary factors, medication use, and diagnoses of CRC and other diseases were obtained prospectively at regular intervals via well-validated questionnaires. The Western dietary pattern was characterized by consumption of red and processed meats, high-fat dairy products (such as whole milk and cream), refined grains, and desserts. The prudent dietary pattern was characterized by high intakes of vegetables, fruits, whole grains, and fish.2Mehta R.S. Song M. Nishihara R. et al.Dietary patterns and risk of colorectal cancer: analysis by tumor location and molecular subtypes.Gastroenterology. 2017; 152: 1944-1953Abstract Full Text Full Text PDF PubMed Scopus (82) Google Scholar In contrast with some previous studies that evaluated individual food items, the present study perhaps provides more "real-world" and practical data that reflect complex dietary patterns that exist in contemporary society. Furthermore, the dietary data were collected prospectively using well-validated dietary description tools, reducing the likelihood of the findings being affected by recall or selection bias.2Mehta R.S. Song M. Nishihara R. et al.Dietary patterns and risk of colorectal cancer: analysis by tumor location and molecular subtypes.Gastroenterology. 2017; 152: 1944-1953Abstract Full Text Full Text PDF PubMed Scopus (82) Google Scholar The combined studies involved 137,217 participants who were followed for up to 32 years, with a total of 3,646,068 person-years of follow-up. During this time, 3260 incident CRCs were documented. Overall, those in the highest quartile for Western dietary pattern consumption, had a 31% increased CRC risk (relative risk [RR], 1.31; 95%, CI 1.15-1.48; P < .0001) compared with those in the lowest quartile. For the prudent dietary pattern, those in the highest quartile had a 14% reduced risk of CRC (RR, 0.86; 95% CI, 0.77-0.95; P = .01) compared with those in the lowest quartile.2Mehta R.S. Song M. Nishihara R. et al.Dietary patterns and risk of colorectal cancer: analysis by tumor location and molecular subtypes.Gastroenterology. 2017; 152: 1944-1953Abstract Full Text Full Text PDF PubMed Scopus (82) Google Scholar The study also enhances our understanding by providing more specific data regarding the association between dietary pattern and tumor location. Of the 2800 tumors with location information available (1264 proximal colon, 866 distal colon, and 670 rectal tumors), the association of Western dietary pattern with CRC incidence was statistically significant for tumors of the distal colon (RR, 1.55; 95% CI, 1.22-1.96; P = .0004) and rectum (RR, 1.35; 95% CI, 1.03-1.77; P = .01), but not for the proximal colon (RR, 1.11; 95% CI, 0.91-1.35; P = .51). There were no differences by anatomic location for prudent dietary pattern scores.2Mehta R.S. Song M. Nishihara R. et al.Dietary patterns and risk of colorectal cancer: analysis by tumor location and molecular subtypes.Gastroenterology. 2017; 152: 1944-1953Abstract Full Text Full Text PDF PubMed Scopus (82) Google Scholar Although the association between Western dietary patterns and distal CRC has been shown previously,10Flood A. Rastogi T. Wirfalt E. et al.Dietary patterns as identified by factor analysis and colorectal cancer among middle-aged Americans.Am J Clin Nutr. 2008; 88: 176-184Crossref PubMed Scopus (117) Google Scholar, 11Kim M.K. Sasaki S. Otani T. et al.Japan Public Health Center-based Prospective Study Group. Dietary patterns and subsequent colorectal cancer risk by subsite: a prospective cohort study.Int J Cancer. 2005; 115: 790-798Crossref PubMed Scopus (85) Google Scholar, 12Wu K. Hu F.B. Fuchs C. et al.Dietary patterns and risk of colon cancer and adenoma in a cohort of men (United States).Cancer Causes Control. 2004; 15: 853-862Crossref PubMed Scopus (87) Google Scholar, 13Slattery M.L. Edwards S.L. Boucher K.M. et al.Lifestyle and colon cancer: an assessment of factors associated with risk.Am J Epidemiol. 1999; 150: 869-877Crossref PubMed Scopus (104) Google Scholar the strengths of the present study by Mehta et al,2Mehta R.S. Song M. Nishihara R. et al.Dietary patterns and risk of colorectal cancer: analysis by tumor location and molecular subtypes.Gastroenterology. 2017; 152: 1944-1953Abstract Full Text Full Text PDF PubMed Scopus (82) Google Scholar including large numbers of participants, prospective data acquisition, high rates of follow-up, use of validated questionnaires, and multivariate analysis add weight to the evidence that a Western dietary pattern is indeed associated with an increased risk of distal CRC. Of further interest, is the novel finding by Mehta et al2Mehta R.S. Song M. Nishihara R. et al.Dietary patterns and risk of colorectal cancer: analysis by tumor location and molecular subtypes.Gastroenterology. 2017; 152: 1944-1953Abstract Full Text Full Text PDF PubMed Scopus (82) Google Scholar that a Western dietary pattern was associated with particular molecular subtypes of CRC. They found that Western dietary patterns seemed to be more strongly associated with KRAS-wildtype, BRAF-wildtype, CIMP-low/negative, and microsatellite stable tumors. In contrast, no such associations were found among participants who had prudent dietary patterns.2Mehta R.S. Song M. Nishihara R. et al.Dietary patterns and risk of colorectal cancer: analysis by tumor location and molecular subtypes.Gastroenterology. 2017; 152: 1944-1953Abstract Full Text Full Text PDF PubMed Scopus (82) Google Scholar However, Western dietary patterns may not have the same association with proximal CRC, a significant proportion of which may arise via the serrated neoplasia pathway.14Rex D.K. Ahnen D.J. Baron J.A. et al.Serrated lesions of the colorectum: review and recommendations from an expert panel.Am J Gastroenterol. 2012; 107 (quiz 4, 30): 1315-1329Crossref PubMed Scopus (814) Google Scholar, 15Leggett B. Whitehall V. Role of the serrated pathway in colorectal cancer pathogenesis.Gastroenterology. 2010; 138: 2088-2100Abstract Full Text Full Text PDF PubMed Scopus (718) Google Scholar Rather, the Western diet seems likely to influence the traditional chromosomal instability-mediated adenoma to carcinoma sequence of CRC.16Aune D. Chan D.S. Vieira A.R. et al.Red and processed meat intake and risk of colorectal adenomas: a systematic review and meta-analysis of epidemiological studies.Cancer Causes Control. 2013; 24: 611-627Crossref PubMed Scopus (123) Google Scholar Future studies may focus on further determining the exact mechanisms by which processed or red meats and other components of the Western diet increase CRC risk. This may lead to increased understanding of potential mechanisms to prevent progression during the adenoma to carcinoma sequence, particularly for distal CRC, and even potential future targets for intervention at the molecular level. In the interim, while strongly encouraging our patients to participate in CRC screening programs, it would also be "prudent" to ensure that they are well-educated to appreciate that their dietary choices can significantly impact their CRC risk. Therefore, how do we now respond to our patients' queries after their colonoscopy, about diet and CRC risk? We now offer the following advice.•We recommend limiting the consumption of processed and red meat, because these are associated with an increased CRC risk. Because we do not yet know the specific amount of processed meat consumption that increases CRC risk, we recommend avoiding processed meats whenever possible. We also recommend limiting red meat consumption to 0.5 servings or 42 g/d of lean red meat.17Pan A. Sun Q. Bernstein A.M. et al.Red meat consumption and mortality: results from 2 prospective cohort studies.Arch Intern Med. 2012; 172: 555-563Crossref PubMed Scopus (7) Google Scholar•We also explain that the benefits of limiting the intake of processed and red meat extend beyond reducing CRC risk. Studies have shown that processed and red meat consumption is associated with an increased risk of cardiovascular disease mortality, cancer-related mortality and total mortality.17Pan A. Sun Q. Bernstein A.M. et al.Red meat consumption and mortality: results from 2 prospective cohort studies.Arch Intern Med. 2012; 172: 555-563Crossref PubMed Scopus (7) Google Scholar, 18Sinha R. Cross A.J. Graubard B.I. et al.Meat intake and mortality: a prospective study of over half a million people.Arch Intern Med. 2009; 169: 562-571Crossref PubMed Scopus (417) Google Scholar Substituting excess red meat with alternatives such as poultry, fish, nuts, legumes, low-fat dairy, and whole grains is associated with a lower mortality risk.17Pan A. Sun Q. Bernstein A.M. et al.Red meat consumption and mortality: results from 2 prospective cohort studies.Arch Intern Med. 2012; 172: 555-563Crossref PubMed Scopus (7) Google Scholar•Finally, even if these dietary recommendations are implemented, we reiterate the importance of achieving a good bowel preparation for their next colonoscopy! Dietary Patterns and Risk of Colorectal Cancer: Analysis by Tumor Location and Molecular SubtypesGastroenterologyVol. 152Issue 8PreviewWestern and prudent dietary patterns have been associated with higher and lower risks of colorectal cancer (CRC), respectively. However, little is known about the associations between dietary patterns and specific anatomic subsites or molecular subtypes of CRC. Full-Text PDF