***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: High prediagnostic serum beta-cryptoxanthin levels have been found to be associated with reduced risk of lung cancer in a recent cohort study of Chinese men in Shanghai , China . Data on dietary beta-cryptoxanthin , and other specific carotenoids and antioxidants in relation to lung cancer , particularly in non-Western population s , are scarce . The aim of the present study was to assess the roles of dietary antioxidants in the development of lung cancer . Between April 1993 and December 1998 , 63,257 Chinese men and women ages 45 - 74 years in Singapore participated in a prospect i ve study of diet and cancer . At baseline , an in-person interview was conducted using a structured question naire for information on usual dietary habits , tobacco smoking , and other lifestyle factors . A Singapore food composition data base was used to estimate intake of alpha-carotene , beta-carotene , beta-cryptoxanthin , lycopene , lutein/zeaxanthin , vitamins A , C , and E , and folate in study subjects . During the first 8 years of follow-up , 482 lung cancer cases occurred among cohort members . High levels of dietary beta-cryptoxanthin were associated with reduced risk of lung cancer ; relative to the lowest quintile , the self-reported smoking adjusted relative risks ( 95 % confidence intervals ) for the highest quintile were 0.73 ( 0.54 - 0.98 ) among all of the subjects and 0.63 ( 0.41 - 0.99 ) among current smokers . Before adjustment for cigarette smoking , dietary vitamin C was associated with a statistically significant reduction in risk of lung cancer . However the inverse vitamin C-lung cancer association was largely explained by smoking and dietary beta-cryptoxanthin . Other carotenoids ( alpha-carotene , beta-carotene , lycopene , and lutein/zeaxanthin ) , vitamins A and E , and folate were not associated significantly with lung cancer risk after adjustment for cigarette smoking . We recognized that potential measurement errors in cigarette smoking may exert an effect on the dietary beta-cryptoxanthin-lung cancer association . After additional adjustments were made for the residual confounding by smoking using statistical models , about 15 - 40 % reduction in risk of lung cancer was seen for subjects in the highest versus lowest 10th percentile of dietary beta-cryptoxanthin . The present study lends additional credence to prior experimental and epidemiological data in support of the hypothesis that dietary beta-cryptoxanthin is a chemopreventive agent for lung cancer in humans Evidence from some previous studies suggests that lipophilic antioxidants , particularly carotenoids , may reduce the risk of breast cancer . We prospect ively investigated the associations of plasma levels of tocopherols , retinol , carotenoids with the risk of developing breast cancer among Chinese women . We conducted a study of 365 incident breast cancer cases and 726 individually matched controls nested within a large cohort study of women aged 40–70 years at baseline . We observed no associations between breast cancer risk and any of the tocopherols , retinol , and most carotenoids . However , high levels of plasma lycopene other than trans , 5- and 7-cis or trans α-cryptoxanthin were inversely associated with the risk of developing breast cancer . Our results do not support an overall protective effect of lipophilic antioxidants  on breast cancer risk . The few inverse associations observed for subtype of carotenoids may need to be confirmed in future studies Lycopene is potentially effective in the prevention of breast cancer from laboratory and observational studies . Among 39,876 women initially free of cardiovascular disease and cancer , we first conducted a prospect i ve cohort study of dietary lycopene and its food sources . Participants completed a baseline food frequency question naire and provided self-reports of breast cancer risk factors . Dietary lycopene levels were divided into quintiles , and lycopene food sources were categorized . During 9.9 years of follow-up , 1,076 breast cancer cases were confirmed by medical record review . In a nested case-control study , we then identified 508 breast cancer cases and 508 controls matched by age , smoking , and follow-up time .  Plasma lycopene and other carotenoids were measured . In the prospect i ve cohort study , women with increasing quintiles of dietary lycopene had multivariate relative risks ( RR ) of breast cancer of 1.00 ( ref ) , 0.95 , 1.00 , 1.10 , and 1.00 ( P , linear trend = 0.71 ) . Women consuming < 1.5 , 1.5 to < 4 , 4 to < 7 , 7 to < 10 , and ≥10 servings/week of tomato-based products had RRs of 1.00 ( ref ) , 1.00 , 1.20 , 1.18 , and 1.16 ( P , linear trend = 0.11 ) . No individual lycopene food sources were associated with breast cancer . In the nested case-control study , women in increasing quartiles of plasma lycopene had multivariate RRs of breast cancer of 1.00 ( ref ) , 0.95 , 1.15 , and 0.93 ( P , linear trend = 0.86 ) . The stepwise addition of individual plasma carotenoids did not impact the RRs for plasma lycopene , nor were other carotenoids associated with breast cancer . In conclusion , neither higher dietary nor plasma lycopene levels were associated with a reduced risk of breast cancer in middle-aged and older women 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 Fruit and vegetable consumption has been hypothesized to reduce the risk of renal cell cancer .  We conducted a pooled analysis of 13 prospect i ve studies , including 1,478 incident cases of renal cell cancer ( 709 women and 769 men ) among 530,469 women and 244,483 men followed for up to 7 to 20 years . Participants completed a vali date d food-frequency question naire at baseline . Using the primary data from each study , the study -specific relative risks ( RR ) were calculated using the Cox proportional hazards model and then pooled using a r and om effects model . We found that fruit and vegetable consumption was associated with a reduced risk of renal cell cancer .  Compared with < 200 g/d of fruit and vegetable intake , the pooled multivariate RR for ≥600 g/d was 0.68 [ 95 % confidence interval ( 95 % CI ) = 0.54 - 0.87 ; P for between- studies heterogeneity = 0.86 ; P for trend = 0.001 ] . Compared with < 100 g/d , the pooled multivariate RRs ( 95 % CI ) for ≥400 g/d were 0.79 ( 0.63 - 0.99 ; P for trend = 0.03 ) for total fruit and 0.72 ( 0.48 - 1.08 ; P for trend = 0.07 ) for  total vegetables . For specific carotenoids , the pooled multivariate RRs ( 95 % CIs ) comparing the highest and lowest quintiles were 0.87 ( 0.73 - 1.03 ) for α-carotene , 0.82 ( 0.69 - 0.98 ) for β-carotene , 0.86 ( 0.73 - 1.01 ) for β-cryptoxanthin , 0.82 ( 0.64 - 1.06 ) for lutein/zeaxanthin , and 1.13 ( 0.95 - 1.34 ) for lycopene . In conclusion , increasing fruit and vegetable consumption is associated with decreasing risk of renal cell cancer ;  carotenoids present in fruit and vegetables may partly contribute to this protection . ( Cancer Epidemiol Biomarkers Prev 2009;18(6):1730–9 BACKGROUND Soy food is a rich source of isoflavones -- a class of phytoestrogens that has both antiestrogenic and anticarcinogenic properties . OBJECTIVE The objective was to evaluate the association of adolescent and adult soy food intake with breast cancer risk in a cohort of 73,223 Chinese women who participated in the Shanghai Women 's Health Study . DESIGN A vali date d food-frequency question naire was used to assess usual dietary intake during adulthood and adolescence . After a mean follow-up of 7.4 y , 592 incident cases of breast cancer were identified for longitudinal analyses by using Cox regressions . RESULTS Adult soy food consumption , measured either by soy protein or isoflavone intake , was inversely associated with the risk of premenopausal breast cancer , and the association was highly statistically significant ( P for trend < 0.001 ) . The multivariate-adjusted relative risks ( RRs ) for the upper intake quintile compared with the lowest quintile were 0.41 ( 95 % CI : 0.25 , 0.70 ) for soy protein intake and 0.44 ( 95 % CI : 0.26 , 0.73 ) for isoflavone intake . High intake of soy foods during adolescence was also associated with a reduced risk of premenopausal breast cancer ( RR : 0.57 ; 95 % CI : 0.34 , 0.97 ) . Women who consumed a high amount of soy foods consistently during adolescence and adulthood had a substantially reduced risk of breast cancer . No significant association with soy food consumption was found for postmenopausal breast cancer . CONCLUSION This large , population -based , prospect i ve cohort study provides strong evidence of a protective effect of soy food intake against premenopausal breast cancer The association between plasma carotenoids and prostate cancer  risk was investigated in a case-control study nested within the prospect i ve Health Professionals Follow-up Study . We matched 450 incident prostate cancer cases diagnosed from 1993–1998 to 450 controls by age , time , month , and year of blood donation . Modest inverse , but not statistically significant , associations were observed among plasma α-carotene , β-carotene , and lycopene concentrations , and overall risk of prostate cancer diagnosis { odds ratio ( highest versus lowest quintile ; OR ) , α-carotene : OR , 0.67 [ 95 % confidence interval ( CI ) , −0.40–1.09 ] ; β-carotene : OR , 0.78 ( 95 % CI , 0.48–1.25 ) ; lycopene : OR , 0.66 ( 95 % CI , 0.38–1.13)}. The inverse association between plasma lycopene concentrations and prostate cancer risk was limited to participants who were 65 years or older ( OR , 0.47 ; 95 % CI , 0.23–0.98 ) and without a family history of prostate cancer ( OR , 0.48 ; 95 % CI , 0.26–0.89 ) . Combining , older age and a negative family history provided similar results ( OR , 0.43 ; 95 % CI , 0.18–1.02 ) . Inverse associations between β-carotene and prostate cancer risk were also found among younger participants ( < 65 years of age ; OR , 0.36 ; 95 % CI , 0.14–0.91 ; Ptrend = 0.03 ) . Combining dietary intake and plasma data confirmed our results . We found a statistically significant inverse association between higher plasma lycopene concentrations and lower risk of prostate cancer , which was restricted to older participants and those without a family history of prostate cancer . This observation suggests that tomato products may exhibit more potent protection against sporadic prostate cancer rather than those with a stronger familial or hereditary component . In addition , our findings also suggest that among younger men , diets rich in β-carotene may also play a protective role in pro 
    Output:
    
Most studies found null associations between individual phytochemicals and cancer risk at various sites .
In addition , results from past studies have been largely inconsistent , and observed associations have been of relatively modest magnitude .
The most consistent protective effects were observed for higher levels -- dietary intake , serum , plasma , or urinary metabolites -- of β-carotene and renal cell cancer , β-cryptoxanthin and lung cancer , isothiocyanates and lung cancer , isothiocyanates and gastrointestinal cancer , lignans and postmenopausal breast cancer , and flavonoids and lung cancer .
Although elevated risk of certain cancers with higher levels of certain phytochemicals was observed , an insufficient pool of studies examining the same associations or inconsistent findings across studies limit the ability to conclude that any one phytochemical increases cancer risk .