***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: Dietary factors have been hypothesized to affect the risk of liver cancer  via various mechanisms , but the influence has been not well studied and the evidence is conflicting . We investigated associations of dietary trace element intake , assessed through a vali date d food frequency question naire , with risk of liver cancer  in two prospect i ve cohort studies of 132,765 women ( 1997 - 2013 ) and men ( 2002 - 2013 ) in Shanghai , China . The associations were first evaluated in cohort studies and further assessed in a case-control study nested within these cohorts adjusting for hepatitis B virus infection . For cohort analyses , Cox proportional hazard models were used to estimate hazard ratios and 95 % confidence intervals . For nested case-control analyses , conditional logistic regression was used to calculate odds ratios and 95 % confidence intervals . After a median follow-up time of 15.2 years for the Shanghai Women 's Health Study and 9.3 years for the Shanghai Men 's Health Study , 192 women and 344 men developed liver cancer .  Dietary intake of manganese was inversely associated with liver cancer risk ( highest vs. lowest quintile , HR = 0.51 , 95 % CI : 0.35 - 0.73 ; ptrend = 0.001 ) . Further adjustment for hepatitis B virus infection in the nested case-control study yielded a similar result ( highest vs. lowest quintile , OR = 0.38 , 95 % CI : 0.21 - 0.69 ; ptrend < 0.001 ) . No significant association was found between dietary intake of selenium , iron , zinc , copper and liver cancer risk . The results suggest that higher intake of manganese may be associated with a lower risk of liver cancer in China There have been few prospect i ve studies relating diet to pancreatic cancer , with most having fewer than 100 cases and only one examining dietary nutrients . The authors prospect ively examined dietary factors hypothesized to be associated with exocrine pancreatic cancer in the Alpha-Tocopherol , Beta-Carotene Cancer Prevention Study cohort in Finl and . Of the 27,111 male smokers aged 50 - 69 years with complete dietary information , as ascertained from a self-administered dietary history question naire given at baseline ( 1985 - 1988 ) , 163 developed pancreatic cancer from 1985 through November 1997 . Cox proportional hazards models were used to estimate smoking- and age-adjusted hazard ratios and 95 % confidence intervals .  Energy-adjusted butter consumption and saturated fat intake  were positively associated with pancreatic cancer ( highest quintile vs. lowest : hazard ratio ( HR ) = 1.40 , 95 % confidence interval ( CI ) : 0.87 , 2.25 ( p trend = 0.04 ) , and HR = 1.60 , 95 % CI : 0.96 , 2.64 ( p trend = 0.02 ) , respectively ) . Energy intake and energy-adjusted carbohydrate intake  were inversely associated with the disease ( highest quintile vs. lowest : HR = 0.62 , 95 % CI : 0.36 , 1.07 ( p trend = 0.05 ) , and HR = 0.62 , 95 % CI : 0.37 , 1.03 ( p trend = 0.02 ) , respectively ) . These results support the hypothesis that a high intake of saturated fat may increase the risk of pancreatic cancer in smokers , while greater intakes of energy and carbohydrate may reduce the risk Selenium status has been inversely associated with  colorectal cancers ( CRC ) and adenomas  . This investigation evaluates the association between selenium supplementation and prevalent and incident colorectal adenomas and CRC detected during the Nutritional Prevention of Cancer trial follow-up . Of the 1,312 r and omized to 200 mcg of selenized yeast of matching placebo , 598 participants underwent endoscopic screening ( flexible sigmoidoscopy or colonoscopy ) for CRC sometime during the follow-up period , which ended in February 1 , 1996 . There was no colorectal screening performed at baseline . Of those screened , 77 % were male ( with a mean age of 62.8 years ) , 42 % were former and 25 % were current smokers .  Adenomas were classified as prevalent ( identified at the first endoscopic examination post-r and omization during the follow-up period ) or incident ( identified at the second or subsequent examination ) . Ninety-nine prevalent and 61 incident adenomas were ascertained . Logistic regression odds ratios ( OR ) and 95 % confidence intervals ( CI ) were calculated , adjusting for age , gender and smoking status . For prevalent adenomas , there was a suggestive but nonsignificant decrease in risk associated with selenium treatment ( OR = 0.67 , 95 % CI = 0.43 - 1.05 ) . Subjects in the lowest tertile of baseline selenium ( OR = 0.27 , 95 % CI = 0.09 - 0.77 ) and current smokers ( OR = 0.27 , 95 % CI = 0.11 - 0.66 ) had significant reductions in risk . The OR for incident adenomas was 0.98 ( 95 % CI = 0.57 - 1.68 ) . In addition to being associated with a reduced risk of incident CRC , selenium supplementation was associated with a significantly reduced risk of prevalent adenomas , but only among subjects with either a low baseline selenium level or among current smokers BACKGROUND Current US dietary recommendations for selenium are based on maximization of plasma glutathione peroxidase ( GSHPx ) activity according to data from one study of Chinese men . OBJECTIVE The effect of various amounts of supplemental selenium on GSHPx activities in blood of New Zeal and adults was investigated to calculate a selenium requirement for New Zeal and ers . The effect on plasma selenoprotein P and thyroid hormones was also investigated . DESIGN Fifty-two adults with low blood selenium concentrations ingested a placebo or 10 , 20 , 30 , or 40 microgram Se as L-selenomethionine daily for 20 wk . RESULTS Plasma and whole-blood GSHPx activities increased in all supplemented groups but reached a plateau only in the group receiving 40 microgram Se , as determined by statistical analysis . Increases in selenoprotein P were greater than those for selenium and GSHPx at all supplement intakes . Thyroxine concentrations decreased in supplemented groups but the decrease was significantly different from that in the control group only for the 10-microgram group and for all supplemented groups combined . CONCLUSIONS An upper estimated requirement of 90 microgram Se/d was calculated as the intake necessary for maximization of plasma GSHPx activity , as used in the derivation of the US recommended daily allowance . Our lower estimated requirement of 39 microgram Se/d was the intake necessary to reach two-thirds of maximal GSHPx activity , as was used in calculating the World Health Organization normative requirement . The lower estimate is a realistic goal for New Zeal and but the upper estimate could be achieved only with regular inclusion of high-selenium foods Objective Limited data are available on the role of mineral intake in the development of  lung cancer ( LC ) . We investigated whether dietary calcium , copper , iron , magnesium , selenium and zinc intake were associated with LC risk . Methods We analyzed data from 5435 participants of the Rotterdam Study , a prospect i ve population -based cohort study among subjects aged 55 years and older . At baseline ( 1990–1993 ) , diet was measured by a vali date d food frequency question naire . LC events were diagnosed on the basis of pathology data and medical records . Hazard ratios ( HRs ) on LC for energy-adjusted mineral intake were calculated using Cox regression models while adjusting for potential confounders . Results During a follow-up period of 22 years , we identified 211 incident cases of LC . A higher zinc intake was associated with 42 % reduction in risk of LC ( top tertile vs. first tertile : HR 0.58 , 95 % CI 0.35 ; 0.94 , P-for trend = 0.039 ) . Similarly , high intake of iron was associated with reduced risk of LC ( top tertile vs. first tertile : HR 0.58 , 95 % CI 0.37 ; 0.92 , P-for trend = 0.021 ) . There was no association between dietary intake of calcium , copper , magnesium and selenium and LC risk . Conclusions Our results suggest that dietary zinc and iron intake are associated with reduced risk of LC . No evidence was found for an association between calcium , copper , magnesium and selenium intake and LC risk BACKGROUND From March 1986 through May 1991 , we conducted a r and omized nutritional intervention trial , the General Population Trial , in Linxian , China , a region with epidemic rates of squamous esophageal and adenomatous gastric cardia cancers . We found that participants who received selenium , beta-carotene , and vitamin E  had significantly lower cancer mortality rates than those who did not . In the current study , we examined the relationship between selenium levels measured in pretrial ( 1985 ) sera from participants and the subsequent risk of developing squamous esophageal , gastric cardia , and gastric non-cardia cancers during the trial . METHODS This study was design ed and analyzed in accord with a stratified case-cohort sampling scheme , with the six strata defined by sex and three age categories . We measured  serum selenium levels in 590 case subjects with esophageal cancer , 402 with gastric cardia cancers , and 87 with gastric non-cardia cancers as well as in 1062 control subjects .  Relative risks ( RRs ) , absolute risks , and population attributable risk for cancers were estimated on the basis of the Cox proportional hazards models . All statistical tests are two-sided . RESULTS We found highly significant inverse associations of serum selenium levels with the incidence of esophageal ( P : for trend < 10(-4 ) ) and gastric cardia ( P : for trend < 10(-6 ) ) cancers . The RR and 95 % confidence interval ( CI ) for comparison of highest to lowest quartile of serum selenium was 0.56 ( 95 % CI = 0.44 - 0.71 ) for esophageal cancer and 0.47 ( 95 % CI = 0.33 - 0.65 ) for gastric cardia cancer . The population proportion of these cancers that is attributable to low selenium levels was 26.4 % ( 95 % CI = 14.45 - 38.36 ) . We found no evidence for a gradient of serum selenium associated with incidence of gastric non-cardia cancer ( P : for trend = .96 ) , with an RR of 1.07 ( 95 % CI = 0.55 - 2.08 ) for the highest to lowest quartile of serum selenium . CONCLUSIONS Our study supports findings from previous prospect i ve studies and r and omized trials that variations in selenium levels affect the incidence of certain cancers . In the United States , where intervention trials of selenium are in the planning stages , consideration should be given to including population s at high risk for squamous esophageal and gastric cardia cancers The association between prostate cancer and baseline vitamin E and selenium was evaluated in the trial-based cohort of the Alpha-Tocopherol , Beta-Carotene Cancer Prevention Study ( n = 29,133 ) . During up to 9 years of follow-up , 317 men developed incident prostate cancer . Multivariate Cox proportional hazards models that adjusted for intervention group , benign prostatic hyperplasia , age , smoking , and urban residence were used to evaluate associations between prostate cancer and exposures of interest . There were no significant associations between baseline serum alpha-tocopherol , dietary vitamin E , or selenium and prostate cancer overall . The associations between prostate cancer and vitamin E and some of the baseline dietary tocopherols differed significantly by alpha-tocopherol intervention status , with the suggestion of a protective effect for total vitamin E among those who received the alpha-tocopherol intervention ( relative risk was 1.00 , 0.68 , 0.80 , and 0.52 for increasing quartiles ; P = 0.07 ) The Nutritional Prevention of Cancer Trial was a r and omized , clinical trial design ed to evaluate the efficacy of selenium as selenized yeast ( 200 microg daily ) in preventing the recurrence of nonmelanoma skin cancer among 1312 residents of the Eastern United States . Original secondary analyses through December 31 , 1993 showed striking inverse associations between treatment and the incidence of total [ hazard ratio ( HR ) = 0.61 , 95 % confidence interval ( CI ) = 0.46 - 0.82 ] , lung , prostate , and colorectal cancer and total cancer mortality . This report presents results through February 1 , 1996 , the end of blinded treatment . Effect modification by baseline characteristics is also evaluated . The effects of treatment overall and within subgroups of baseline age , gender , smoking status , and plasma selenium were examined using incidence rate ratios and Cox proportional hazards models . Selenium supplementation 
    Output:
    
The findings in this study suggest that selenium  is protective against cancer however the effects vary with different cancers