***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: Deficiencies of selenium have been associated with an increased cancer risk , and several clinical and animal trials have suggested that improved selenium nutrition may reduce the incidence of several kinds of cancer , including lung , colorectal , and breast . Results from recent trials also show an anticarcinogenic effect of selenium in the prostate . There is converging evidence from epidemiologic , experimental animal , and molecular biology studies for an antitumor effect of selenium . Evidence suggests there are two modes of action of selenium affecting cancer risk : first , by functioning as an essential nutrient that provides the catalytic centers of a number of selenoenzymes , including some with antioxidant and redox functions ; second , by serving as a source of selenium metabolytes that affect carcinogenesis in other ways . The first mechanism appears most relevant to protection against cancer initiation , the second against cancer progression . There is conclusive evidence of the increased risk of prostate cancer for a male with a family history of the disease . As a result of this evidence , and the evidence supporting the chemopreventive properties of selenium , this study proposed that a trial to test the effect of selenium on men at high risk for development of prostate cancer is appropriate . This article describes the Australian Prostate Cancer Prevention Trial Using Selenium ( APPOSE ) trial to test the hypothesis that daily dietary supplementation with selenium will reduce prostate cancer incidence in a population of men who are at increased risk because of a first-degree relative with prostate cancer In many observational studies , a higher intake of individual antioxidants is inversely associated with  lung cancer risk . Data from in vitro and animal experiments suggest that there are biochemical interactions among antioxidant nutrients ; therefore , consideration of multiple antioxidants simultaneously may be important in terms of risk estimation . The authors constructed a dietary antioxidant index and evaluated its ability to predict lung cancer risk within the Alpha-Tocopherol , Beta-Carotene Cancer Prevention Study cohort . At baseline ( 1985 - 1988 ) , 27,111 Finnish male smokers aged 50 - 69 years completed a dietary question naire that assessed usual frequency of consumption and portion sizes for the previous 12 months . A total of 1,787 incident cases of lung cancer were identified during a follow-up period of up to 14.4 years ( 1985 - 1999 ) . Principal components analyses were individually applied to the carotenoid , flavonoid , and vitamin E nutrient groups , and summation of retained principal component scores , plus selenium and vitamin C , yielded the composite antioxidant index . In multivariate proportional hazards models , the relative risks for lung cancer according to increasing quintiles of the antioxidant index were 1.00 ( referent ) , 1.00 ( 95 % confidence interval ( CI ) : 0.87 , 1.14 ) , 0.91 ( 95 % CI : 0.79 , 1.05 ) , 0.79 ( 95 % CI : 0.68 , 0.92 ) , and 0.84 ( 95 % CI : 0.72 , 0.98 ) ( p for trend = 0.002 ) . These findings support the hypothesis that a combination of dietary antioxidants reduces lung cancer risk in male smokers The purpose of this study was to evaluate the effect of selenium ( Se ) in the prevention of  human primary liver cancer .  Three intervention trials were conducted among the residents at high risk to primary liver cancer ( PLC ) in Qidong county , Jiang-su province , the People ’s Republic of China . This area has the second highest rate of PLC in China . One trial was undertaken among the general population in a township with supplement of table salt fortified with 15 ppm anhydrous sodium selenite ( Se-salt ) for 5 y and the other four townships with similar PLC incidence rate served as the controls using normal table salt . The second trial was undertaken among hepatitis B virus surface antigen carriers ( HBVsAg+ ) receiving supplement of 200 μg Se in form of selenized , yeast ( Se-yeast ) daily vs placebo for 4 y. The third trial was carried out in members of families with high PLC incidence  using Se-yeast ( 200 μg of Se daily ) vs placebo for 2 y. The results showed that nutritional supplement of Se could reduce the PLC incidence significantly Objective To investigate the association between selenium and the risk of Barrett ’s esophagus ( BE ) , the precursor lesion of esophageal adenocarcinoma . Methods Data from the prospect i ve Netherl and s Cohort Study were used . This cohort study was initiated in 1986 , when 120,852 subjects aged 55–69 years completed a question naire on dietary habits and lifestyle  , and provided toenail clippings for the determination of baseline selenium status . After 16.3 years of follow-up , 253 BE cases ( identified through linkage with the nationwide Dutch pathology registry ) and 2,039 subcohort members were available for case – cohort analysis . Cox proportional hazards models were used to calculate incidence rate ratios ( RR ) . Results The multivariable-adjusted RR for the highest versus the lowest quartile of toenail selenium  was 1.06 ( 95 % CI 0.71–1.57 ) . No dose – response trend was seen ( p trend = 0.99 ) . No association was found in subgroups defined by sex , smoking status , body mass index ( BMI ) , or intake of antioxidants . For BE cases that later progressed to high- grade dysplasia or adenocarcinoma , the RR for a  selenium level above the median vs. below the median was 0.64 ( 95 % CI 0.24–1.76 ) . Conclusions In this large prospect i ve cohort study , we found no evidence of an association between  selenium and risk of BE Oxidative stress may enhance prostatic carcinogenesis . A polymorphism [ valine ( V ) -- > alanine ( A ) ] of manganese superoxide dismutase ( MnSOD ) , the primary antioxidant enzyme in mitochondria , has been recently associated with prostate cancer . We examined the relationship between prostate cancer and the MnSOD polymorphism and its interactions with baseline plasma antioxidant levels ( selenium , lycopene , and alpha-tocopherol ) and beta-carotene treatment among 567 cases and 764 controls nested in the prospect i ve Physicians ' Health Study . We found little overall association between MnSOD polymorphism and prostate cancer risk ; however , this polymorphism significantly modified risk of prostate cancer associated with prediagnostic plasma antioxidants ( P(interaction ) > or = 0.05 ) . Among men with the AA genotype , high selenium level ( 4th versus 1st quartile ) was associated with a relative risk ( RR ) of 0.3 [ 95 % confidence interval ( CI ) , 0.2 - 0.7 ] for total prostate cancer ; for clinical ly aggressive prostate cancer , the RR was 0.2 ( 95 % CI , 0.1 - 0.5 ) . In contrast , among men with the VV/VA genotype , the RRs were 0.6 ( 0.4 - 1.0 ) and 0.7 ( 0.4 - 1.2 ) for total and clinical ly aggressive prostate cancer . These patterns were similar for lycopene and alpha-tocopherol and were particularly strong when these antioxidants and selenium were combined ; men with the AA genotype had a 10-fold gradient in risk for aggressive prostate cancer across quartiles of antioxidant status . Men with AA genotype who were r and omly assigned to beta-carotene treatment ( versus placebo ) had a RR of 0.6 ( 95 % CI , 0.2 - 0.9 ; P(interaction ) = 0.03 ) for fatal prostate cancer , but no significant association was observed in men with the VV/VA genotype . Both endogenous and exogenous antioxidants play an important and interdependent role in preventing clinical ly significant prostate cancer BACKGROUND Some evidence indicates that a low selenium intake may be associated with an increased risk of  prostate cancer .  OBJECTIVE The aim of this study was to investigate the association of plasma  selenium  concentration with subsequent prostate cancer risk and to examine this association by stage and grade of disease and other factors . DESIGN A nested case-control study was performed among men in the European Prospect i ve Investigation into Cancer and Nutrition ( EPIC ) . The association between plasma selenium concentration and prostate cancer risk was assessed in 959 men with incident prostate cancer and 1059 matched controls . RESULTS Overall , plasma selenium concentration was not associated with prostate cancer risk ; the multivariate relative risk for men in the highest fifth of selenium concentration compared with the lowest fifth was 0.96 ( 95 % CI : 0.70 , 1.31 ; P for trend = 0.25 ) . There were no significant differences in the association of plasma selenium with risk when analyzed by stage or grade of disease . Similarly , the association of selenium with risk did not differ by smoking status or by plasma alpha- or gamma-tocopherol concentration . CONCLUSION Plasma selenium concentration was not associated with prostate cancer risk in this large cohort of European men BACKGROUND Inadequate plasma selenium can adversely affect the maintenance of optimal health ; therefore , reported decreases in plasma selenium in an aging population are cause for concern . To further examine this hypothesis , we explored the relationships between plasma selenium and mortality in an elderly population : the EVA ( Etude du Vieillissement Artériel ) study . METHODS The EVA study was a 9-year longitudinal study with 6 periods of follow-up . During the 2-year period from 1991 to 1993 ( EVA0 ) , 1389 men and women born between 1922 and 1932 were recruited . The effects of plasma selenium at baseline on mortality were determined by Cox proportional hazards regression analysis , adjusting for the following variables : sociodemographic characteristics , dietary habits , health , and cognitive factors . RESULTS During the 9-year follow-up , 101 study participants died . Baseline plasma selenium was higher in individuals who were alive at the end of follow-up [ mean ( SD ) , 1.10 ( 0.20 ) micromol/L ] than in those who died during the follow-up [ 1.01 ( 0.20 ) micromol/L ; P < 10(-4 ) ] . Mortality rates were significantly higher in individuals with low selenium [ increments = 0.2 micromol/L ; relative risk ( RR ) = 1.56 ( 95 % confidence interval , 1.28 - 1.89 ) ] . After we controlled for various potential confounding factors , this association remained significant [ RR = 1.54 ( 1.25 - 1.88 ) ] . When the underlying causes of death were considered , we found an association with cancer-related mortality [ adjusted RR = 1.79 ( 1.32 - 2.44 ) ] . CONCLUSIONS Even if it is premature to present selenium as a longevity indicator in an elderly population , our results are in accordance those of large , interventional , r and omized trials with selenium , which suggest that this essential trace element plays a role in health maintenance in aging individuals BACKGROUND Multivitamin supplements are used by millions of Americans because of their potential health benefits , but the relationship between multivitamin use and prostate cancer is unclear . METHODS We prospect ively investigated the association between multivitamin use and risk of prostate cancer ( localized , advanced , and fatal ) in 295,344 men enrolled in the National Institutes of Health (NIH)-AARP Diet and Health Study who were cancer free at enrollment in 1995 and 1996 . During 5 years of follow-up , 10,241 participants were diagnosed with incident prostate cancer , including 8765 localized and 1476 advanced cancers . In a separate mortality analysis with 6 years of follow-up , 179 cases of fatal prostate cancer were ascertained . Multivitamin use was assessed at baseline as part of a self-administered , mailed food-frequency question naire .  Relative risks ( RRs ) and 95 % confidence intervals ( CIs ) were calculated by use of Cox proportional hazards regression , adjusted for established or suspected prostate cancer risk factors . RESULTS No association was observed between  multivitamin use and risk of localized prostate cancer . However , we found an increased risk of advanced and fatal prostate cancers ( RR = 1.32 , 95 % CI = 1.04 to 1.67 and RR = 1.98 , 95 % CI = 1.07 to 3.66 , respectively ) among men reporting excessive use of multivitamins  ( more than seven times per week ) when compared with never users . The incidence rates per 100,000 person-years for advanced and fatal prostate cancers for those who took a multivitamin more than seven times per week were 143.8 and 18.9 , respectively , compared with 113.4 and 11.4 in never users . The positive associations with excessive multivitamin use were strongest in men with a family history of prostate cancer or who took individual micronutrient supplements , including selenium , beta-carotene , or zinc . CONCLUSION These results suggest that regular multivitamin use is not associated with the risk of early or localized prostate cancer . The possibility that men taking high levels of multivitamins along with other supplements have increased risk of advanced and fatal prostate cancers is of concern and merits further evaluation Abstract Objective : To conduct timely epidemiologic investigations of molecular/genetic markers that may contribute to the development of prostate , lung , colorectal , or other cancers within the Selenium and Vitamin E Can 
    Output:
    
The results of the Nutritional Prevention of Cancer Trial ( NPCT ) and SELECT raised concerns about possible harmful effects of selenium supplements .
No reliable conclusions can be drawn regarding a causal relationship between low selenium exposure and an increased risk of cancer .
To date , there is no convincing evidence that selenium supplements can prevent cancer in men , women or children