***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: OBJECTIVE --To evaluate the long term efficacy of diets in lowering  serum cholesterol concentration .  DESIGN --Descriptive overview of 16 published controlled trials of six months ' duration or longer . SETTING --Trials had been conducted in hospital clinics ( 6 ) , industry ( 3 ) , mental hospitals or institutions ( 3 ) , and in general population s ( 4 ) . PATIENTS --Trials had been conducted in high risk subjects ( 5 ) , in unselected healthy subjects ( 6 ) , or for secondary prevention in patients with coronary heart disease ( 5 ) . Women were included in only four trials . INTERVENTIONS --Diets equivalent to the step 1 diet were employed in eight trials , with individual intervention by dietitians ( 3 ) or occupational physicians ( 2 ) or with population advice ( 3 ) . Intensive diets which were more rigorous than the step 2 diet were employed in eight trials . MAIN OUTCOME MEASURES --Net change in serum total cholesterol concentration in subjects receiving treatment with diet compared with values in control subjects after six months to 10 years . RESULTS --In five trials with the step 1 diet as individual intervention the net reduction in serum cholesterol concentration ranged from 0 % to 4.0 % over six months to six years . In trials with population education reductions in cholesterol concentrations were 0.6 - 2.0 % over five to 10 years . When population and individual dietary advice were combined changes in cholesterol concentration ranged from a fall of 2.1 % to a rise of 1.0 % over four to 10 years . Diets more intensive than the step 2 diet reduced serum cholesterol concentration by 13 % over five years in selected high risk men in the population ; by 6.5 - 15.1 % over two to five years in hospital out patients ; and by 12.8 - 15.5 % over one to four and a half years in patients in institutions . CONCLUSIONS --The response to a step 1 diet is too small to have any value in the clinical management of adults with serum cholesterol concentrations above 6.5 mmol/l . Current guidelines recommend screening of serum cholesterol concentration in healthy subjects , followed by treatment with a step 1 diet . The guidelines should be review ed to provide a more realistic estimate of the effect of a step 1 diet and of the likely need for lipid lowering drugs Diet is an important factor in the causation of cancer . Previous systematic review s of one-to-one interventions to encourage dietary change have found that such interventions can achieve modest improvements in diet . However , such interventions are re source intensive and unlikely to be good value for money at a population level . Interventions that address groups , communities or whole population s may be less re source intensive and effect change in a wider population . We report a systematic review of such interventions . We set wide inclusion criteria , including before- and -after studies and studies with a non-r and omized comparison group as well as r and omized trials . We found eighteen studies based in the community , seventeen based on worksites , five based in churches and one based in a supermarket . Interventions which targeted fruit and vegetable intake were most likely to be successful , particularly in worksites and churches . There was also evidence of small positive effects on reducing fat intake in worksites and churches . Overall the community-based interventions showed little effect . The studies included in the present review were generally poorly reported . Dietary changes are reported in the relatively short-term studies review ed here but may not be sustained in the long term . The effects that we have identified are small but the reach is potentially very wide , in some cases as wide as a whole country . The cost effectiveness of such strategies remains to be evaluated A controlled intervention trial , with the purpose of testing the hypothesis that the incidence of coronary heart disease ( CHD ) could be decreased by the use of serum-cholesterol-lowering ( SCL ) diet , was carried out in 2 mental hospitals near Helsinki in 1959 - -71 . The subjects were hospitalized middle-aged men . One of the hospitals received the SCL diet , i.e. a diet low in saturated fats and cholesterol and relatively high in polyunsaturated fats , while the other served as the control with a normal hospital diet . Six years later the diets were reversed , and the trial was continued another 6 years . The use of the SCL diet was associated with markedly lowered serum-cholesterol values . The incidence of CHD , as measured by the appearance of certain electrocardiographic patterns and by the occurrence of coronary deaths , was in both hospitals during the SCL-diet periods about half that during the normal-diet periods . An examination of a number of potential confounding variables indicated that the changes in them were small and failed to account for the considerable reduction in the incidence of CHD . It is concluded that the use of the serum-cholesterol-lowering diet exerted a substantial preventive effect on CHD 
    Output:
    
Dietary advice appears to be effective in bringing about modest beneficial changes in diet and cardiovascular risk factors over approximately 12 months , but longer-term effects are not known