***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: 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 the Physicians ' Health Study , a r and omized , placebo-controlled , double-blind trial of aspirin in the reduction of cardiovascular mortality and beta-carotene in decreasing cancer incidence , 33,223 subjects were eligible and willing to enter the trial . Instead of r and omizing this group immediately , all participants received identical calendar packs that contained active aspirin and beta-carotene placebo . Following an 18-week run-in , only 22,071 subjects who remained eligible and willing and had taken at least 2/3 of their pills were r and omized . We estimated the effect of the run-in as follows : pill taking compliance increased 20 - 41 per cent ; sample size decreased 34 per cent ; duration of follow-up decreased 7 per cent which result ed in a 7 per cent decrease in the expected event rate for the placebo group . To estimate these changes , we made assumptions about compliance and outcome risk for those excluded by the run-in . Our conclusion , however , about the net effect of the run-in on the power of the study remains constant across variations in a number of those assumptions . The power with the run-in , with 22,071 good compliers was typically higher , and never more than negligibly lower , than the power without the run-in , with 33,223 good and poor compliers . In addition , savings from enrolling 11,152 fewer subjects in the trial result ed from the use of the run-in Background —In apparently healthy people , the relation between blood pressure and risk of subsequent cardiovascular disease ( CVD ) is linear . In persons with CVD , the relation is uncertain . Methods and Results —We conducted a prospect i ve study of 5218 older women with CVD who reported their blood pressure at baseline in the Women ’s Antioxidant Cardiovascular Study ( WACS ) , an ongoing double-blind , placebo-controlled secondary prevention trial of the benefits and risks of antioxidant vitamins , folic acid , vitamin B6 , and vitamin B12 among women with CVD or ≥3 coronary risk factors . A total of 661 confirmed CVD events ( nonfatal myocardial infa rct ion , nonfatal stroke , coronary artery bypass graft procedure , percutaneous coronary angioplasty , or CVD death ) occurred during a median follow-up of 6.5 years . After controlling for age , r and omized treatment assignment , antihypertensive medication use , and coronary risk factors , we found that systolic blood pressure ( SBP ) was a strong predictor of CVD events and that the relation between SBP and CVD risk was positive , continuous , and linear ( P for linear trend=0.001 ) . For each 10-mm Hg increment in SBP , there was a 9 % ( 95 % CI 4 % to 15 % ) increase in risk of secondary CVD events . Diastolic blood pressure , mean arterial pressure , and pulse pressure were weaker predictors of CVD risk in this cohort , and joint consideration of SBP and diastolic blood pressure found that only SBP significantly predicted risk . Use of antihypertensive medication did not modify the relationship of SBP with CVD events . Conclusions —In this population of women with CVD , we observed a strong , continuous , and linear association between SBP and risk of secondary CVD events . SBP was the blood pressure measure most strongly related to CVD risk Helicobacter pylori infection is associated with histological gastritis , gastric atrophy , gastric cancer and mucosa-associated lymphoid tissue lymphoma in the stomach . However , gastric cancer only develops in a minority of infected individuals . Such clinical diversity is caused by variations in the interactions between H. pylori pathogenicity , host susceptibility , and environmental factors . Based on evidence from three prospect i ve epidemiological studies , the International Agency for Research on Cancer and the World Health Organization ( IARC/WHO ) concluded in 1994 that H. pylori has a causal linkage to gastric carcinogenesis and is a definite carcinogen in humans . Two large-scale , prospect i ve , epidemiological studies have recently been reported in Japan and have confirmed that H. pylori infection constitutes a high risk factor for the development of gastric cancer , at least in males . In order to obtain evidence that eradication of H. pylori leads to a reduction in the occurrence of gastric cancer , reversibility of precancerous lesions , gastric atrophy or intestinal metaplasia should be proven after eradication treatment . A biopsy specimen from the lesser curvature of the corpus is the most sensitive for evaluating the regression of gastric atrophy on histology , and the evaluation needs be conducted at least 13 months after treatment . In a Mongolian gerbil model with or without low-dose chemical carcinogens , it has been demonstrated that H. pylori can lead to the development of gastric cancer . Experimental studies have eluci date d that virulence factors of H. pylori interact with gastric epithelial cell signaling related to carcinogenesis . The cag pathogenicity isl and ( cagPAI ) is a major virulence gene cluster ; it encodes the type IV secretion machinery system forming a cylinder-like structure . The CagA protein is translocated into target cells via this secretion system and induces a hummingbird phenotype , a growth factor-like effect . The other gene products are probably translocated into target cells and accelerate cellular proliferation and apoptosis . The molecular mechanism of the interaction between H. pylori and gastric epithelial cells may provide a new strategy for effective prevention of the development of gastric cancer induced by H. pylori infection 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 Lower lobe origin and histologic diagnosis of adenocarcinoma have been described as useful parameters for attributing lung cancer to prior asbestos exposure . To assess whether these characteristics differed between asbestos-exposed individuals and smokers , we evaluated lobe of origin and histologic type of tumors in 78 asbestos-exposed and 214 nonexposed heavy smokers developing lung cancer during the Carotene and Retinol Efficacy Trial ( CARET ) , a prospect i ve cancer chemoprevention trial . Most tumors in both cohorts , regardless of radiographic fibrosis at baseline , originated in upper lobes , representing 67 % in asbestos-exposed and 80 % in smokers , respectively ( adjusted OR for lower lobe = 1.41 ; 95 % CI = 0.69 - 2.91 ) . Adenocarcinoma represented 32 % of lung tumors in the asbestos cohort , and 30 % in the smoking cohort ( adjusted OR = 0.78 ; 95 % CI = 0.40 - 1.55 ) , and was inversely associated with radiographic fibrosis ( adjusted OR = 0.19 ; 95 % CI = 0.06 - 0.62 ) . We conclude that neither anatomic site nor histologic cell type of tumors distinguishes effectively between smoking and asbestos as causal factors in development of lung cancer High consumption of fruits and vegetables has been associated with a lower risk of pancreatic cancer in many case-control studies . However , cohort studies on this relationship are limited and do not support an association . We examined the associations of overall consumption of fruits and vegetables and consumption of certain subgroups of fruits and vegetables with the  incidence of pancreatic cancer among 81,922 women and men in the Swedish Mammography Cohort and the Cohort of Swedish Men .  Hazard ratios ( HR ) with 95 % confidence intervals ( 95 % CI ) were estimated using Cox proportional hazards models . During an average follow-up of 6.8 years ( 1998 - 2004 ) , 135 incident pancreatic cancer cases were diagnosed . After adjustment for age and other risk factors for pancreatic cancer , the HRs for the highest compared with the lowest category of intake were 1.13 ( 95 % CI , 0.66 - 1.94 ) for total fruits and vegetables , 1.10 ( 95 % CI , 0.64 - 1.88 ) for total fruits , and 1.08 ( 95 % CI , 0.63 - 1.85 ) for total vegetables . Among specific subgroups of fruits and vegetables , a nonsignificant inverse association was observed with cruciferous vegetable consumption  ( ≥3 servings/wk versus < 1 serving/wk : HR , 0.70 ; 95 % CI , 0.43 - 1.13 ) . Cabbage consumption was associated with a statistically significant lower risk of pancreatic cancer ( ≥1 serving/wk versus never consumption : HR , 0.62 ; 95 % CI , 0.39 - 0.99 ) . Findings from this prospect i ve study do not support a relationship of overall fruit and vegetable consumption with pancreatic cancer risk . The association between consumption of cruciferous vegetables and pancreatic cancer risk warrants further investigation . ( Cancer Epidemiol Biomarkers Prev 2006;15(2):301–5 BACKGROUND Both hyper- and hypokalemia increase cardiovascular risk . Modest hyperkalemia is common with angiotensin-converting enzyme inhibition . We studied post-hoc the association of an initial , on-treatment serum potassium measurement with subsequent cardiovascular outcomes over 4.5 years in 9297 individuals at high cardiovascular risk , r and omized to an ACE inhibitor or to placebo .  METHODS Post-hoc analysis of cardiovascular outcomes , as related to serum potassium levels , in the HOPE ( Heart Outcomes and Prevention Evaluation ) study which compared ramipril to placebo , and included 692 patients with a serum potassium level > 5.0 mM and 137 with a serum potassium level < 3.5 mM , defined as hyper- and hypokalemia , respectively .  Serum potassium  was measured 1 month after start of r and omized treatment . RESULTS With hyperkalemia , the primary event rate was unchanged compared to normokalemia ( 15.5 vs 15.7 % , p > 0.4 , respectively ) , with hypokalemia , the primary event rate was higher ( 22.6 % vs 15.5 % , respectively , p = 0.023 ) . The hazard ratio for the primary outcome associated with this initial hypokalemia was 1.44 ( 1.00 - 2.06 ) on multivariate analysis . The combined primary outcome ( myocardial infa rct ion , cardiovascular death , stroke ) was not different throughout deciles of serum potassium but the lowest and highest deciles included many with normokalemia . R and omized treatment was withheld because of hyperkalemia in 8 and 6 people allocated to ramipril and placebo , respectively . The benefit of ramipril on cardiovascular outcomes was independent of serum potassium , but ramipril reduced hypokalemia in the entire cohort ( 1.15 vs 1.86 % with placebo , p = 0.005 ) , particularly in those participants on diuretics ( 3.8 % vs 6.5 % , p = 0.07 ) . CONCLUSIONS In patients at high cardiovascular risk , modest hypokalemia predicts a less favorable outcome while modest hyperkalemia does not . Ramipril reduces hypokalemia and decreases risk 
    Output:
    
We could not find convincing evidence that antioxidant supplements prevent gastrointestinal cancers .
On the contrary , antioxidant supplements seem to increase overall mortality .