***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Some serrated polyps of the colorectum are likely preinvasive lesions , evolving through a newly recognized serrated pathway to colorectal cancer . To assess possible risk and protective factors for serrated polyps and particularly to explore differences in risk factors between polyps in the right and left colorectum , we pooled data from three large multicenter chemoprevention trials . A serrated polyp was defined broadly as any serrated lesion ( hyperplastic , sessile serrated adenoma , “ traditional ” serrated adenoma , mixed adenoma ) diagnosed during each trial 's main treatment period of ∼3 to 4 years . Using generalized linear regression , we computed risk ratios and 95 % confidence intervals as measures of the association between risk for serrated polyps and demographic , lifestyle , and dietary variables . Of the 2,830 subjects that completed at least one follow-up exam after r and omization , 675 ( 23.9 % ) had at least one left-sided serrated polyp and 261 ( 9.2 % ) had at least one right-sided lesion . In the left colorectum , obesity , cigarette smoking , dietary fat , total energy intake , and red meat intake were associated with an increased risk for serrated polyps . In the right colon , aspirin treatment was associated with a reduced risk and family history of polyps and folate treatment were associated with an increased risk for serrated polyps . Our results suggest that several common lifestyle and dietary variables are associated with risk for serrated polyps , and some of these may differ for the right and left colorectum . ( Cancer Epidemiol Biomarkers Prev 2009;18(8):2310–7 OBJECTIVE : The aim of this study was to determine the relationship between fat , fiber , and meat intake , and risk of colorectal adenoma recurrence .  METHODS : We determined  adenoma recurrence and dietary intake for 1,520 participants in two r and omized trials : The Antioxidant Polyp Prevention Study and Calcium Polyp Prevention Study . Subjects underwent baseline colonoscopy with removal of all adenomas , and dietary intake was estimated with a vali date d semiquantitative food frequency question naire . Follow-up colonoscopy was performed 1 and 4 yr later . Pooled risk ratios for adenoma recurrence were obtained by generalized linear regression , with adjustment for age , sex , clinical center , treatment category , study , and duration of observation . RESULTS : In the total colorectum , fiber intake was weakly and nonsignificantly associated with a risk for all adenomas ( RR quartile 4 vs quartile 1 = 0.85 , 95 % CI 0.69–1.05 ) and advanced adenomas ( RR = 0.88 , 95 % CI 0.54–1.44 ) . Associations were stronger for adenomas in the proximal colon ( RR = 0.73 , 95 % CI 0.56–0.97 ) and some fiber subtypes ( fruit and vegetable , grain ) . There was no association between fat or total red meat intake and risk of adenoma or advanced adenoma recurrence . However , when considering other meats , risk ( quartile 4 vs quartile 1 ) for advanced adenoma was increased for processed meat ( RR = 1.75 , 95 % CI 1.02–2.99 ) and decreased for chicken ( RR = 0.61 , 95 % CI 0.38–0.98 ) . CONCLUSION : The inverse associations between fiber intake and risk of adenoma recurrence we observed are weak , and not statistically significant . Our data indicate that intake of specific meats may have different effects on risk Many N-nitroso compounds ( NOC ) are carcinogens . In this controlled study of 21 healthy male volunteers , levels of NOC on a high ( 420 grams ) red meat diet were significantly greater ( P = 0.001 ) than on a low ( 60 grams ) meat diet but not significantly greater when an equivalent amount of vegetable protein was fed . An 8-mg supplement of haem iron also increased fecal NOC ( P = 0.006 ) compared with the low meat diet , but 35-mg ferrous iron had no effect . Endogenous N-nitrosation , arising from ingestion of haem but not inorganic iron or protein , may account for the increased risk associated with red meat consumption in colorectal cancer Cooking meats at high temperatures and for long duration produces heterocyclic amines and other mutagens . These meat-derived mutagenic compounds have been hypothesized to increase risk of colorectal neoplasia , but prospect i ve data are unavailable . We examined the association between intakes of the heterocyclic amines 2-amino-3,8-dimethylimidazo[4,5,-f]quinoxaline ( MeIQx ) , 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine ( PhIP ) , 2-amino-3,4,8-trimethylimidazo[4,5,-f]quinoxaline ( DiMeIQx ) , and meat-derived mutagenicity ( MDM ) and risk of distal colon adenoma using a cooking method question naire  administered in 1996 in the Health Professionals Follow-up Study cohort . Between 1996 and 2002 , 581 distal colon adenoma cases were identified . Higher intake of MDM was marginally associated with increased risk of distal adenoma [ fourth versus lowest quintile : odds ratio ( OR ) , 1.39 ; 95 % confidence interval ( 95 % CI ) , 1.05 - 1.84 ; highest versus lowest quintile : OR , 1.29 ; 95 % CI , 0.97 - 1.72 ; Ptrend = 0.08 ] . Adjusting for total red meat or processed meat intake did not explain those associations . Our data also suggested a positive association between higher MeIQx ( highest versus lowest quintile : OR , 1.28 ; 95 % CI , 0.95 - 1.71 ; Ptrend = 0.22 ) and risk of adenoma , but this association was attenuated after adjusting for processed meat intake . DiMeIQx and PhIP did not seem to be associated with risk of adenoma . In conclusion , higher consumption of mutagens from meats cooked at higher temperature and longer duration may be associated with higher risk of distal colon adenoma independent of overall meat intake . Because mutagens other than heterocyclic amines also contribute to MDM , our results suggest that mutagens other than heterocyclic amines in cooked meats may also play a role in increasing the risk of distal adenoma . ( Cancer Epidemiol Biomarkers Prev 2006;15(6):1120–5 Diet has long been thought to be an important factor in the etiology of colorectal cancer . The specific dietary nutrients or factors responsible for this disease , the second leading cause of cancer death in the United States [ 1 ] , have not , however , been clearly eluci date d. Colorectal adenomatous polyps ( here referred to as polyps ) are generally considered to be precursor lesions for most cases of colorectal carcinoma [ 2 - 4 ] ; however , little is known about their risk factors . Since the introduction of fiberoptic endoscopy , especially colonoscopy , attention has focused on the potential for preventing colorectal cancer by screening for and resecting the adenomas [ 5 , 6 ] . Because of their high recurrence rate after resection [ 7 , 8 ] , these polyps have been used as an end point for the study of potential chemopreventive agents . Four studies have explored potential dietary risk factors for incident colorectal adenomatous polyps [ 9 - 12 ] . No previous observational studies have explored the role of diet or other lifestyle factors in the recurrence of polyps after polypectomy . We discuss the results of a casecontrol study of colorectal polyps among patients from three colonoscopy practice s and analyze dietary risk factors for both incident and recurrent polyps . Methods Our study sample included patients having colonoscopy at three colonoscopy practice s in New York City between April 1986 and March 1988 . In total , 2988 patients were evaluated . Of these , 2443 ( 81.8 % ) were eligible for our study ( patients had to be between 35 and 84 years of age ; reside in New York , New Jersey , or Connecticut ; speak English or Spanish ; and have colonoscopy to at least the splenic flexure ) . The colonoscopists completed data sheets indicating the reason for colonoscopy and the clinical findings at the time of colonoscopy . The study pathologist review ed slides of all suspected neoplastic lesions . All eligible participants received a letter signed by their colonoscopist introducing the study . A trained interviewer then contacted and interviewed participants by telephone . Alternatively , the question naire was mailed for self-completion and was followed by a telephone interview to resolve any remaining questions . An earlier study indicated that the results obtained for dietary factors were similar for both interview methods [ 13 ] . The interview itself consisted of a general question naire that focused on demographic characteristics , medical history , lifestyle , family history , and other topics . The dietary interview consisted of the Block food frequency question naire and specified food intake for a period 3 to 5 years before the colonoscopy [ 14 ] . Ultimately , 1956 dietary question naires were completed ( 80.1 % of eligible patients ) . Of these , 71 % were conducted by telephone , and 29 % were returned by mail . An incident case of adenomatous polyps was defined as an eligible participant with no history of colon carcinoma , adenomatous polyps , or inflammatory bowel disease who was found to have one or more pathologically defined polyps on the index colonoscopy . The incident control group consisted of persons who were found to be free of colorectal neoplasia on index colonoscopy and who were without a history of adenomatous polyps , colon cancer , or inflammatory bowel disease . A case of recurrent polyps was defined as an eligible participant with a self-reported history of one or more polyps who had a pathologically confirmed polyp on the index colonoscopy . The recurrent control was defined as a participant whose index colonoscopy showed no colorectal neoplasia but who had a history of one or more polyps . Cases and controls with a history of colorectal cancer or inflammatory bowel disease were excluded . Although we did not have pathologic confirmation of all initial polyps , we did obtain pathology reports on a r and om sample of 100 recurrent cases and controls and found 97 to be adenomatous . By these criteria , 286 incident cases ( 162 men and 124 women ) and 480 incident controls ( 210 men and 270 women ) were identified , whereas 186 recurrence cases ( 130 men and 56 women ) and 330 recurrence controls ( 187 men and 143 women ) were found . Food item and nutrient data were generated by software programs provided by Block and coworkers [ 14 ] at the National Cancer Institute . The main analyses were done using logistic regression modelling and maximum likelihood ratios [ 15 ] in the BMDP-LR program . Analyses were conducted separately for men and women . Age , Quetelet index , and caloric intake were entered as covariates for most analyses . A previous study by our group had shown obesity , as measured by Quetelet index , to be a risk factor for polyps among women ; the trend for men was not significant [ 16 ] . Analyses in which nutrients were st and ardized per 1000 kilocalories were also done for comparison [ 17 ] . For each nutrient or food group , quartiles were defined by review of the control group data ; the lowest quartile was given a reference value of 1.0 , and odds ratios were calculated for each of the other quartiles , with 95 % confidence intervals ( CIs ) for the highest-to-lowest quartile comparison . The probability of a linear trend was calculated by entering the four quartiles as ordered categories . Results The case and control groups for the incidence and recurrence studies were generally similar in age distribution and education . Table 1 shows a comparison of the characteristics of the case and control groups for both the incident and recurrent groups . Most polyps were 5 mm or larger in size and had at least some degree of atypia . The site distribution of the incident polyps showed a preponderance to the left . Most incident case and control participants had colonoscopy because of overt or occult rectal bleeding . A larger proportion of the recurrent polyps were right-sided ( P = 0.005 ) . The time interval from initial polypectomy to index colonoscopy  was 4.3 years for cases and 3.7 years for controls ( P > 0.2 ) . Table 1 . Polyp Characteristics for Incident and Recurrent Cases Tables 2 and 3 show the odds ratios by quartile , using the lowest quartile as the referent group , for some of the 15 nutrients and food groups evaluated . The results for vegetables , red meat , beef , cheese , protein , vitamin C , and carotene are not shown ; however , no consistent differences were found . Table 2 . Odds Ratios of Incident Polyps by Quartile of Selected Nutrients and Food Groups , Adjusted for Age , Quetelet Index , and Caloric Intake Table 3 . Odds Ratios of Recurrent Polyps by Quartile of Selected Nutrients and Food Groups , Adjusted for Age , Quetelet Index , and Caloric Intake Men The only dietary risk factor statistically associated with the risk for colorectal adenomatous polyps in men was caloric intake ; however , this association 
    Output:
    
There was evidence of a nonlinear association between red meat ( pnonlinearity < 0.001 ) and processed meat ( pnonlinearity = 0.01 ) intake and colorectal adenoma risk .