***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 
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    Input: Hyperinsulinemia may explain excess colorectal cancer among individuals who are overweight or inactive . Recent studies have observed elevated colorectal cancer risk among individuals with elevated insulin levels 2 hours after oral glucose challenge or with elevated plasma C-peptide levels . The effect of consuming a high glycemic diet on colorectal risk , however , remains uncertain . Two prospect i ve cohort studies , the Nurses ' Health Study and the Health Professionals Follow-up Study , contributed up to 20 years of follow-up . After exclusions , 1,809 incident colorectal cancers were available for analyses .  Dietary glycemic load ( GL ) was calculated as a function of glycemic index ( postpr and ial blood glucose response as compared with a reference food ) , carbohydrate content , and frequency of intake of individual foods reported on food frequency question naires . Multivariable Cox proportional hazards models were used to adjust for potential confounders . Intakes of dietary carbohydrate , GL , overall glycemic index , sucrose , and fructose were not associated with  colorectal cancer risk in women . A small increase in risk was observed in men with high dietary GL ( multivariate relative risk , 1.32 ; 95 % confidence interval , 0.98 - 1.79 ; highest versus lowest quintile ) , sucrose or fructose ( multivariate relative risk , 1.37 ; 95 % confidence interval , 1.05 - 1.78 ; highest versus lowest quintile of fructose , P = 0.008 ) . Associations were slightly stronger among men with elevated body mass index ( > or = 25 kg/m(2 ) ) . Results among women were similar after stratifying by body mass index or physical activity . High intakes of GL , fructose , and sucrose were related to an elevated  colorectal cancer risk among men . For women , however , these factors did not seem to increase the risk of colorectal cancer The determine the effect of different foods on the blood glucose , 62 commonly eaten foods and sugars were fed individually to groups of 5 to 10 healthy fasting volunteers .  Blood glucose levels were measured over 2 h , and expressed as a percentage of the area under the glucose response curve when the same amount of carbohydrate was taken as glucose . The largest rises were seen with vegetables ( 70 + /- 5 % ) , followed by breakfast cereals ( 65 + /- 5 % ) , cereals and biscuits ( 60 + /- 3 % ) , fruit ( 50 + /- 5 % ) , dairy products ( 35 + /- 1 % ) , and dried legumes ( 31 + /- 3 % ) . A significant negative relationship was seen between fat ( p less than 0.01 ) and protein ( p less than 0.001 ) and postpr and ial glucose rise but not with fiber or sugar content To investigate the relation of dietary intakes of sucrose , meat , and fat , and anthropometric , lifestyle , hormonal , and reproductive factors to colon cancer incidence , data were analyzed from a prospect i ve cohort study of 35,215 Iowa ( United States ) women , aged 55–69 years and without a history of cancer , who completed mailed dietary and other question naires in 1986 . Through 1990 , 212 incident cases of colon cancer were documented . Proportional hazards regression was used to adjust for age and other risk factors . Risk factors found to be associated significantly with colon cancer included : ( i ) sucrose-containing foods and beverages other than ice cream/milk ;  relative risks ( RR ) across the quintiles=1.00 , 1.73 , 1.56 , 1.54 , and 2.00 ( 95 % confidence intervals [ CI ] for quintiles two and five exclude 1.0 ) ; ( ii ) sucrose ; RR across the quintiles=1.00 , 1.70 , 1.81 , 1.82 , and 1.45 ( CI for quintiles two through four exclude 1.0 ) ; ( iii ) height ; RR=1.23 for highest to lowest quintile ( P for trend-0.02 ) ; ( iv ) body mass index ; RR=1.41 for highest to lowest quintile ( P for trend=0.03 ) ; and ( v ) number of livebirths , RR=1.59 for having had one to two livebirths and 1.80 for having had three or more livebirths compared with having had none ( P for trend=0.04 ) . These data support hypotheses that sucrose intake or being tall or obese increases colon cancer risk ; run contrary to the hypothesis that increased parity decreases risk ; support previous findings of no association with demographic factors other than age , cigarette smoking , or use of oral contraceptives or estrogen replacement therapy ; and raise questions regarding previous associations with meat , fat , protein , and physical activity . Cancer Causes and Control 1994 , 5 , 38–52 Although diet is believed to influence colorectal cancer risk , the long-term effects of a diet with a high glycemic load are unclear . The growing recognition that colorectal cancer may be promoted by hyperinsulinemia and insulin resistance suggests that a diet inducing high blood glucose levels and an elevated insulin response may contribute to a metabolic environment conducive to tumor growth . We prospect ively followed a cohort of 38 451 women for an average of 7.9 years and identified 174 with incident colorectal cancer . We used baseline dietary intake measurements  , assessed with a semiquantitative food-frequency question naire , to examine the associations of  dietary glycemic load , overall dietary glycemic index , carbohydrate , fiber , nonfiber carbohydrate , sucrose , and fructose with the subsequent development of colorectal cancer . Cox proportional hazards models were used to estimate relative risks ( RRs ) . Dietary glycemic load was statistically significantly associated with an increased risk of colorectal cancer ( adjusted RR = 2.85 , 95 % confidence interval [ CI ] = 1.40 to 5.80 , comparing extreme quintiles of dietary glycemic load ; P(trend ) = .004 ) and was associated , although not statistically significantly , with overall glycemic index ( corresponding RR = 1.71 , 95 % CI = 0.98 to 2.98 ; P(trend ) = .04 ) . Total carbohydrate ( adjusted RR = 2.41 , 95 % CI = 1.10 to 5.27 , comparing extreme quintiles of carbohydrate ; P(trend ) = .02 ) , nonfiber carbohydrate ( corresponding RR = 2.60 , 95 % CI = 1.22 to 5.54 ; P(trend ) = .02 ) , and fructose ( corresponding RR = 2.09 , 95 % CI = 1.13 to 3.87 ; P(trend ) = .08 ) were also statistically significantly associated with increased risk . Thus , our data indicate that a diet with a high dietary glycemic load may increase the risk of colorectal cancer in women The relation between diet and female colorectal cancer was analyzed in a prospect i ve study of 14,727 women aged 34 - 65 years , who were enrolled at mammographic screening clinics in New York and Florida from 1985 to 1991 . They were followed through the end of 1994 ( average 7.1 yrs ) by a combination of direct contact through mail and telephone and record linkages with regional tumor registries , result ing in 100 incident cases of colorectal cancer . There was no overall positive or inverse association of colorectal cancer risk with intakes of total calories , total or subclasses of fat , carbohydrate , or dietary fiber , whereas there was an inverse association with total protein . Among major food groups , there was a progressive decline in risk of colorectal cancer with increasing intake of fish and shellfish ( relative risk for 4th vs. 1st quartile = 0.49 , 95 % confidence interval = 0.27 - 0.89 ) . A similar inverse association was also observed for consumption of dairy products , and this association was explained mainly by calcium , not by other nutrients , such as fat or protein . The results of the present study indicated that certain dietary components of fish or dairy products may protect against colorectal cancer , whereas the relations with red meat or total fat remained unclear 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 
    Output:
    
Conclusion This meta- analysis of cohort studies does not support an independent association between diets high in carbohydrate , glycemic index , or glycemic load and colorectal cancer risk