***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: This case – cohort study examined the association between plasma enterolactone concentration and  incidence of colon and rectal cancer in the Diet , Cancer and Health cohort , which enrolled 57,053 participants aged 50–64 . Information about diet and lifestyle was obtained by question naire , and data on prescriptions of antibiotics were obtained from the Danish Prescription Registry . Cases diagnosed during 5.9 years of follow-up and a r and omly selected sample of the cohort had a plasma sample analyzed for enterolactone by time-resolved fluoro-immuno assay . Associations were analyzed by Cox proportional hazards model . A total of 244 colon cancer cases , 137 rectal cancer cases , and 370 sub-cohort members were included in the statistical analyses . For each doubling in enterolactone concentration , we found lower risk of colon cancer among women [ IRR ( 95 % CI ) = 0.76 ( 0.60–0.96 ) ] and a tendency toward lower risk of rectal cancer [ IRR ( 95 % CI ) = 0.83 ( 0.60–1.14 ) ] . Among men , a doubling in enterolactone tended to be associated with higher risk of colon cancer [ IRR ( 95 % CI ) = 1.09 ( 0.89–1.34 ) ] and was associated with statistically significantly higher risk of rectal cancer [ IRR ( 95 % CI ) = 1.74 ( 1.25–2.44 ) ] . Exclusion of antibiotics users strengthened the results slightly . In conclusion , with higher enterolactone levels , we found lower risk of colon cancer among women and higher risk of rectal cancer among men Enterolignans are phytoestrogenic compounds derived from the conversion of dietary lignans by the intestinal microflora that may be protective against cardiovascular diseases and cancer . To evaluate the use of enterolignans as biomarkers of dietary lignan intake , we studied the relation between plasma and dietary lignans . We determined the dietary intake of 4 lignans ( secoisolariciresinol ( SECO ) , matairesinol ( MAT ) , pinoresinol , and lariciresinol ) using the European Prospect i ve Investigation into Cancer and Nutrition FFQ , and plasma enterodiol ( END ) and enterolactone ( ENL ) concentrations were determined by liquid chromatography-t and em mass spectrometry . The population consisted of 637 men and women , aged 19 - 75 y , participating in a case-control study on colorectal adenomas . Participants did not use antibiotics in the preceding calendar year . We found a modest association between lignan intake and plasma END ( Spearman r = 0.09 , P = 0.03 ) and ENL ( Spearman r = 0.18 , P < 0.001 ) . The correlation of total lignan intake with plasma enterolignans was slightly stronger than that of only SECO plus MAT . The plasma concentrations of both END and ENL were associated with intake of dietary fiber and vegetable protein but not with intake of other macronutrients . The relation between lignan intake and plasma END was modulated by age and previous use of antibiotics , whereas for ENL , it was modulated by weight , current smoking , and frequency of defecation . However , even when we included these nondietary factors in the regression models , the explained variance in plasma END and ENL remained low ( 2 and 13 % , respectively ) BACKGROUND Test results on the bioavailability of isoflavones in the aglycone or glucoside form in Eastern and Western human subjects are contradictory . OBJECTIVE The objective was to investigate the bioavailability of the soy isoflavones daidzein and genistein in American women with typical American dietary habits after ingestion of the aglycone or glucoside form of isoflavones . DESIGN Fifteen American women aged 46 + /- 6 y participated in a r and omized , double-blind study . Blood sample s were collected 0 , 1 , 2 , 4 , 8 , 12 , 24 , and 48 h after consumption of aglycone or glucoside tablets with breakfast . The plasma curves for daidzein , genistein  , and equol  were constructed and the postpr and ial maximum concentration ( C(max ) ) , time to the maximum concentration ( t(max ) ) , and area under the curve ( AUC ) were determined . RESULTS  Isoflavone concentrations peaked early ( 1 - 2 h ) in plasma and peaked again at 4 - 8 h. Mean C(max ) , t(max ) , and AUC values for genistein were not significantly different after ingestion of aglycone or glucoside . However , C(max ) and AUC values , but not t(max ) , were significantly higher for daidzein after aglycone ingestion , which was partly due to its higher content in the aglycone tablets . Equol appeared after 4 h and remained elevated after 48 h. Despite a higher content of daidzein in the aglycone tablets , the AUC for equol was significantly higher after ingestion of the glucoside tablets , probably because of the metabolic action of intestinal bacteria during the long intestinal transit time of glucoside . CONCLUSION The apparent bioavailability of genistein and daidzein is not different when consumed as either aglycone or glucoside by American women Enterolignans are biphenolic compounds that possess several biologic activities whereby they may influence carcinogenesis . The authors investigated the association between plasma enterolactone and enterodiol and  colorectal cancer risk in a Dutch prospect i ve study . Among more than 35,000 participants aged 20 - 59 years , 160 colorectal cancer cases were diagnosed after 7.5 years of follow-up ( 1987 - 2003 ) . Cohort members who were frequency-matched to the cases on age , sex , and study center were selected as controls ( n = 387 ) . Plasma enterodiol and enterolactone were not associated with risk of colorectal cancer after adjustment for known colorectal cancer risk factors ( highest quartile vs. lowest : for enterodiol , odds ratio = 1.11 , 95 % confidence interval : 0.56 , 2.20 ( p-trend = 0.75 ) ; for enterolactone , odds ratio = 1.70 , 95 % confidence interval : 0.88 , 3.27 ( p-trend = 0.15 ) ) . However , sex ( p-interaction = 0.06 ) and body mass index ( p-interaction < 0.01 ) modified the relation between plasma enterolactone and colorectal cancer risk ; increased risks were observed among women and subjects with a high body mass index . The association between plasma enterodiol and colorectal cancer risk was modified by smoking status ; risk was increased among current smokers ( p-interaction < 0.01 ) . These findings do not support the hypothesis that high plasma enterodiol or enterolactone concentrations are associated with reduced risk of colorectal cancer Several experimental studies have reported that the anticarcinogenic properties of dietary soy play an important role in preventing colorectal cancer . However , few epidemiologic studies have examined this association in general population s and their findings have been inconsistent . We investigated the association between dietary soy and isoflavone intake and incidence of colorectal cancer in a prospect i ve cohort study of 83,063 Japanese men and women , ages 45 to 74 years .  Dietary soy and isoflavone intake was measured through a vali date d food frequency question naire in 1995 and 1998 . Throughout 2004 , a total of 886 cases of colorectal cancer were newly identified ( 291 proximal colon , 286 distal colon , and 277 rectum ) . The hazard ratios and 95 % confidence intervals ( 95 % CIs ) were estimated by fitting a Cox proportional hazards model . The intake of isoflavones , miso soup , and soy food was not associated with colorectal cancer in either men or women . By colorectal cancer subsite , the risk of proximal colon cancer in men decreased with increasing consumption of isoflavones , miso soup , and soy food . Compared with men in the lowest quartiles of isoflavones , miso soup , and soy food intake , the hazard ratios in the highest quartiles were 0.55 ( 95 % CI , 0.33 - 0.92 ) , 0.72 ( 95 % CI , 0.43 - 1.21 ) , and 0.51 ( 95 % CI , 0.30 - 0.87 ) , respectively . The results showed no association for distal colon and rectal cancer in men or for subsites of colorectal cancer in women . These findings suggest that the intake of isoflavones , miso soup , and soy food has no substantial effect on the  risk of colorectal cancer in Japanese men and women . ( Cancer Epidemiol Biomarkers Prev 2008;17(8):2128–35 Abstract : The relationship of the intake of soy products and the incidence of  colon cancer  was prospect ively evaluated in a population -based cohort study in Japan . The total intake of soy products and isoflavones in a daily diet was estimated from a vali date d question naire administered at the baseline . The participation rate of the question naire was 92.0 % . The participants were followed from 1992 to 2000 , and colon cancer diagnoses were identified at the main hospitals in the study area . In the analysis , 13,894 men and 16,327 women were included . The medians for energy-adjusted soy product intake were 85.52 g/day for men and 79.60 g/day for women . During follow-up , 111 men and 102 women were diagnosed with colon cancer . A Cox-proportional hazard model was applied to assess the risk of colon cancer incidence . Among women , the risk was reduced with an increased soy product  consumption  ;  the hazard ratio in the highest tertile was 0.56 ( 95 % CI 0.34–0.92 ) compared as the lowest tertile ( trend : P = 0.04 ) , after adjusting for multiple potential confounders . Among men , no significant association was observed . Our results exhibited the weak benefit of soy foods  only among women . Further research to confirm our results may be beneficial Dietary phytoestrogens are suggested to reduce the risk of prostate and colorectal cancer , but the results of epidemiologic studies have not yielded consistent support for this proposed effect , possibly due to inadequate data bases of phytoestrogen levels in foods . Biomarkers of phytoestrogen intakes may provide a clearer insight into the relationship between phytoestrogen exposure and the risk of prostate or colorectal cancer risks . From the European Prospect i ve into Cancer-Norfolk cohort ( ages 45 - 75 ) , serum and urine sample s were analyzed for seven phytoestrogens [ daidzein , enterodiol , enterolactone , genistein , glycitein , O-desmethylangolensin ( O-DMA ) , and equol ] among 193 cases of prostate cancer and 828 controls , and 221 cases of colorectal cancer with 889 controls . Summary variables of total lignans ( enterodiol and enterolactone ) and total isoflavones ( daidzein , genistein , O-DMA , equol , and glycitein ) were created and analyzed in conjunction with individual phytoestrogens . Logistic regression analyses revealed that there was no significant association between prostate cancer risk and total serum isoflavones [ odds ratio ( OR ) , 1.01 ; 95 % confidence interval ( CI ) , 0.93 - 1.10 ] or total serum lignans ( OR , 0.94 ; 95 % CI , 0.86 - 1.04 ) or between colorectal cancer risk and total serum isoflavones ( OR , 1.01 ; 95 % CI , 0.94 - 1.08 ) or total serum lignans ( OR , 1.03 ; 95 % CI , 0.94 - 1.12 ) . Similarly , null associations were observed for individual serum phytoestrogens and for all urinary phytoestrogen biomarkers . In conclusion , we have found no evidence to support an inverse association between phytoestrogen exposure and prostate or colorectal cancer risk . ( Cancer Epidemiol Biomarkers Prev 2008;17(10):2891–4 In vitro and in vivo laboratory data point to chemoprotective effects of flavonoids on  colorectal cancer .  However , there has been limited epidemiologic research on the dietary intake of flavonoids and risk of  colorectal cancer .  Recent expansions of dietary data bases to include flavonoid data now make such studies feasible . Association between the six main classes of flavonoids and the risk of colorectal cancer  was examined using data from a national prospect i ve case-control study in Scotl and , including 1,456 incident cases and 1,456 population -based controls matched on age , sex , and residence area .  Dietary , including flavonoid data , were obtained from a vali date d , self-administered food frequency question naire . Risk of colorectal cancer was estimated using conditional logistic regression models in the whole sample and stratified by sex , smoking status , and cancer site and adjusted for established and putative risk factors . After energy 
    Output:
    
A non-linear inverse association with colorectal cancer risk was found for lignans intake , but no association for circulating enterolactone concentrations was observed .
Thus , study heterogeneity precludes a rigorous conclusion regarding an effect of high exposure to isoflavones on risk of colorectal cancer .