***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: 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 BACKGROUND We tested the hypothesis that dietary intervention can inhibit the development of recurrent colorectal adenomas , which are precursors of most large-bowel cancers . METHODS We r and omly assigned 2079 men and women who were 35 years of age or older and who had had one or more histologically confirmed colorectal adenomas removed within six months before r and omization to one of two groups : an intervention group given intensive counseling and assigned to follow a diet that was low in fat ( 20 percent of total calories ) and high in fiber ( 18 g of dietary fiber per 1000 kcal ) and fruits and vegetables ( 3.5 servings per 1000 kcal ) , and a control group given a st and ard brochure on healthy eating and assigned to follow their usual diet . Subjects entered the study after undergoing complete colonoscopy and removal of adenomatous polyps ; they remained in the study for approximately four years , undergoing colonoscopy one and four years after r and omization . RESULTS A total of 1905 of the r and omized subjects ( 91.6 percent ) completed the study . Of the 958 subjects in the intervention group and the 947 in the control group who completed the study , 39.7 percent and 39.5 percent , respectively , had at least one recurrent adenoma ; the unadjusted risk ratio was 1.00 ( 95 percent confidence interval , 0.90 to 1.12 ) . Among subjects with recurrent adenomas , the mean ( + /-SE ) number of such lesions was 1.85+/-0.08 in the intervention group and 1.84+/-0.07 in the control group . The rate of recurrence of large adenomas ( with a maximal diameter of at least 1 cm ) and advanced adenomas ( defined as lesions that had a maximal diameter of at least 1 cm or at least 25 percent villous elements or evidence of high- grade dysplasia , including carcinoma ) did not differ significantly between the two groups . CONCLUSIONS Adopting a diet that is low in fat and high in fiber , fruits , and vegetables does not influence the risk of recurrence of colorectal adenomas BACKGROUND In observational studies , individuals with high intakes of fruits and vegetables containing beta-carotene experience lower risks of developing cancer . However , the few r and omized trials of beta-carotene supplementation show no overall benefits ; some even suggest harm . This trial was design ed to test the effects of  beta-carotene supplementation in women . METHODS The Women 's Health Study is a r and omized , double-blind , placebo-controlled trial originally testing aspirin , vitamin E , and beta-carotene in the prevention of cancer and cardiovascular disease among 39 876 women aged 45 years or older . The beta-carotene component was terminated early after a median treatment duration of 2.1 years ( range = 0.00 - 2 . 72 years ) . Statistical tests were two-sided . RESULTS Among women r and omly assigned to receive beta-carotene ( 50 mg on alternate days ; n = 19 939 ) or placebo ( n = 19 937 ) , there were no statistically significant differences in incidence of cancer , cardiovascular disease , or total mortality after a median of 4.1 years ( 2.1 years ' treatment plus another 2.0 years ' follow-up ) . There were 378 cancers in the beta-carotene group and 369 cancers in the placebo group ( relative risk [ RR ] = 1.03 ; 95 % confidence interval [ CI ] = 0.89 - 1 . 18 ) . There were no statistically significant differences for any site-specific cancer or during years 1 and 2 combined and years 3 and up combined . For cardiovascular disease , there were no statistically significant differences for myocardial infa rct ion ( 42 in the beta-carotene group versus 50 in the placebo group ) , stroke ( 61 versus 43 ) , deaths from cardiovascular causes ( 14 versus 12 ) , or the combined end point of these three events ( 116 versus 102 ; among women with more than one event , only the first was counted ) . Deaths from any cause were similar in the two groups ( 59 versus 55 ) . Among smokers at baseline ( 13 % of all women ) , there were no statistically significant differences in overall incidence of cancer ( RR = 1.11 ; 95 % CI = 0.78 - 1.58 ) or cardiovascular disease ( RR = 1.01 ; 95 % CI = 0 . 62 - 1.63 ) . CONCLUSION Among apparently healthy women , there was no benefit or harm from beta-carotene supplementation for a limited period on the incidence of cancer and of cardiovascular disease BACKGROUND Epidemiologic evidence indicates that diets high in carotenoid-rich fruits and vegetables , as well as high serum levels of vitamin E ( alpha-tocopherol ) and beta carotene , are associated with a reduced risk of lung cancer .  METHODS We performed a r and omized , double-blind , placebo-controlled primary -prevention trial to determine whether daily supplementation with alpha-tocopherol , beta carotene , or both would reduce the incidence of lung cancer and other cancers .  A total of 29,133 male smokers 50 to 69 years of age from southwestern Finl and were r and omly assigned to one of four regimens : alpha-tocopherol ( 50 mg per day ) alone , beta carotene ( 20 mg per day ) alone , both alpha-tocopherol and beta carotene , or placebo . Follow-up continued for five to eight years . RESULTS Among the 876 new cases of lung cancer diagnosed during the trial , no reduction in incidence was observed among the men who received alpha-tocopherol ( change in incidence as compared with those who did not , -2 percent ; 95 percent confidence interval , -14 to 12 percent ) . Unexpectedly , we observed a higher incidence of lung cancer among the men who received beta carotene than among those who did not ( change in incidence , 18 percent ; 95 percent confidence interval , 3 to 36 percent ) . We found no evidence of an interaction between alpha-tocopherol and beta carotene with respect to the incidence of lung cancer . Fewer cases of prostate cancer were diagnosed among those who received alpha-tocopherol than among those who did not . Beta carotene had little or no effect on the incidence of cancer other than lung cancer . Alpha-tocopherol had no apparent effect on total mortality , although more deaths from hemorrhagic stroke were observed among the men who received this supplement than among those who did not . Total mortality was 8 percent higher ( 95 percent confidence interval , 1 to 16 percent ) among the participants who received beta carotene than among those who did not , primarily because there were more deaths from lung cancer and ischemic heart disease . CONCLUSIONS We found no reduction in the incidence of lung cancer among male smokers after five to eight years of dietary supplementation with alpha-tocopherol or beta carotene . In fact , this trial raises the possibility that these supplements may actually have harmful as well as beneficial effects The association between vegetable and fruit consumption and  stomach cancer  risk was investigated in the Netherl and s Cohort Study among 120,852 men and women aged 55 - 69 years at the start in September 1986 . Analyses were based on 282 incident stomach cancer cases after 6.3 years of follow-up . Age- and sex-adjusted rate ratios of stomach cancer in increasing quintiles of combined vegetable and fruit consumption were 1.00 , 0.70 , 0.65 , 0.76 , and 0.64 ( p trend = 0.04 ) . Multivariate analysis result ed in rate ratios that were somewhat closer to one ( p trend = 0.14 ) . Furthermore , inverse associations for total vegetables , pulses , raw leafy vegetables , total fruit , citrus fruit , and apples and pears that were observed in crude analyses became weaker or disappeared in multivariate analyses .  Total vegetable , but not fruit , consumption was significantly lower in cases diagnosed in the first follow-up year . In analyses limited to first year cases ( resembling a case-control study ) , rate ratios for increasing tertiles of total vegetable consumption were 1.00 , 0.17 , and 0.18 ( p trend = 0.0001 ) , which may indicate the presence of information bias in case-control studies . This prospect i ve study suggests that vegetable and fruit consumption was not clearly associated with  stomach cancer risk in the Dutch population . The findings of this study are comparable with findings of other cohort studies , but they do not support the findings of case-control studies High rates of  hepatitis B virus ( HBV ) infection  and  primary liver cancer ( PLC )  are present in Qidong county . Epidemiological surveys demonstrated an inverse association between selenium ( Se ) level and regional cancer incidence , as well as HBV infection . Four-year animal studies showed that dietary supplement of Se reduced the HBV infection by 77.2 % and liver precancerous lesion by 75.8 % of ducks , caused by exposure to natural environmental etiologic factors . An intervention trial was undertaken among the general population of 130,471 . Individuals in five townships were involved for observation of the preventive effect of Se . The 8-yr follow-up data showed reduced PLC incidence by 35.1 % in selenized table salt supplemented vs the nonsupplemented population . On withdrawal of Se from the treated group , PLC incidence rate began to increase . However , the inhibitory response to HBV was sustained during the 3-yr cessation of treatment . The clinical study among 226 Hepatitis B Surface Antigen (HBsAg)-positive persons provided either 200 μg of Se in the form of selenized yeast tablet or an identical placebo of yeast tablet daily for 4 yr showed that 7 of 113 subjects were diagnosed as having PLC in the placebo group , whereas no incidence of PLC was found in 113 subjects supplemented with Se . Again on cessation of treatment , PLC developed at a rate comparable to that in the control group , demonstrating that a continuous intake of Se is essential to sustain the chemopreventive effect Epidemiological and experimental studies have indicated that dietary factors such as vitamin C , vitamin E , and beta-carotene are associated with the risk of  colorectal cancer . This study was carried out within the Alpha-Tocopherol , Beta-Carotene Cancer Prevention Study ( ATBC Study ) , whose participants were r and omly assigned to four supplementation groups : ( a ) alpha-tocopherol ( AT ) , 50 mg/day ; ( b ) beta-carotene ( BC ) , 20 mg/day ; ( c ) both AT and BC ; and ( d ) placebo . We included the 15,538 ATBC Study participants who had been r and omized within the areas of three major cities in southern Finl and . Cases of colorectal adenoma ( n = 146 ) were identified by the pathology laboratories in the study areas , and these participants ' medical records were collected and review ed . Alpha-tocopherol supplementation increased the risk for adenomas ( relative risk , 1.66 ; 95 % confidence interval , 1.19 - 2.32 ) , whereas beta-carotene supplementation had no effect on the risk ( relative risk , 0.98 ; 95 % confidence interval , 0.71 - 1.35 ) . Slightly more prediagnosis rectal bleeding and intestinal pain occurred in those adenoma cases who received alpha-tocopherol supplements than in those who did not . Thus , some bias may have result ed , with alpha-tocopherol supplementation leading to more colonoscopies and , thus , to an increased detection of incident polyps in this group . This is further supported by the trial finding that alpha-tocopherol supplementation did not increase the risk of colorectal cancer BACKGROUND Observational studies suggest that people who consume more fruits and vegetables containing beta carotene have somewhat lower risks of cancer and cardiovascular disease , and earlier basic research suggested plausible mechanisms . Because large r and omized trials of long duration were necessary to test this hypothesis directly , we conducted a trial of beta carotene supplementation . METHODS In a r and omized , double-blind , placebo-controlled trial of beta carotene ( 50 mg on alternate days ) , we enrolled 22,071 male physicians , 
    Output:
    
Low- quality trials showed no significant effect of  antioxidant supplementation  on mortality .
INTERPRETATION We could not find evidence that antioxidant supplements can prevent gastrointestinal cancers ; on the contrary , they seem to increase overall mortality .