***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: BACKGROUND Even though dietary fiber has been hypothesized to reduce the risk of coronary heart disease , few large epidemiological studies have examined this relation with good methodology . METHODS AND RESULTS The Alpha-Tocopherol , Beta-Carotene Cancer Prevention Study was a r and omized , double-blind , placebo-controlled trial with daily supplementation of alpha-tocopherol and /or beta-carotene . Of the participants , 21930 smoking men aged 50 to 69 years who were free of diagnosed cardiovascular disease and had completed a vali date d dietary question naire at baseline were followed for 6.1 years . We monitored the incidence of major coronary events ( a combination of first nonfatal myocardial infa rct ion and coronary heart disease death ; n = 1399 ) and mortality from coronary heart disease ( n = 635 ) . Both entities had a significant inverse association with  dietary fiber  , but the association was stronger for coronary death . For men in the highest quintile of total dietary fiber intake ( median , 34.8 g/d ) , the relative risk for coronary death was 0.69 ( 95 % confidence interval , 0.54 to 0.88 ; P < .001 for trend ) compared with men in the lowest quintile of intake ( median , 16.1 g/d ) . With an adjustment for known cardiovascular risk factors , intake of saturated fatty acids , beta-carotene , vitamin C , and vitamin E did not material ly change the result . Water-soluble fiber was slightly more strongly associated with reduced coronary death than water-insoluble fiber , and cereal fiber also had a stronger association than vegetable or fruit fiber . CONCLUSIONS These findings suggest that independent of other risk factors , greater intake of foods rich in fiber can substantially reduce the risk of coronary heart disease , and particularly coronary death , in middle-aged , smoking men The individual effects of dietary cholesterol and fat saturation on plasma lipoprotein concentrations were determined in an ethnically diverse population of normolipidemic young men ( 52 Caucasian , 32 non-Caucasian ) . The experimental diets contained approximately 200 or 600 mg/d of cholesterol , 36 - 38 % of calories as fat , and high or low proportions of saturated and polyunsaturated fat ( polyunsaturated/saturated fat ratio approximately 0.8 vs 0.3 ) . At the lower cholesterol intake , the high saturated fat diet had only a modest effect on LDL cholesterol in Caucasians ( + 6 mg/dl-1 ) and none in non-Caucasians . 600 mg cholesterol with high saturated fat led to a substantial mean increase in LDL cholesterol , which was significantly greater in Caucasian than in non-Caucasian subjects ( + 31 mg/dl vs 16 mg/dl , P < 0.005 ) . 600 mg cholesterol with increased polyunsaturated fat gave a mean LDL increase of 16 mg/dl , lower than found when the same high cholesterol intake was coupled with increased saturated fat . Variation in cholesterol rather than the proportions of saturated and polyunsaturated fat had the most influence on LDL-cholesterol levels . Among non-Caucasians it was the only significant factor Twenty-three young adult males were fed diets containing either 400 or 1400 mg of cholesterol per day under controlled conditions for 4 wk . There were minimal differences between the two diets in total protein , carbohydrate , fat , and the P/S fatty acid ratio . In both diets 400 mg of cholesterol was supplied from nonegg food sources ; the additional 1000 mg of cholesterol was from four whole eggs . Blood sample s were collected after a 12- to 14-h fast at the beginning of the study , weekly throughout the experimental period , and 1 wk after completion of the study . Plasma total cholesterol and triglycerides and high-density , low-density , and very low-density lipoprotein cholesterol levels were measured . No significant differences in plasma total cholesterol , triglycerides , and lipoprotein cholesterol levels were observed between groups at any time . However , plasma cholesterol and cholesterol content of individual lipoproteins varied considerably among the individual subjects fed the high cholesterol diet . The importance of changes in the properties and metabolic activity of individual lipoproteins induced by dietary cholesterol with or without gross changes in the cholesterol levels remains to be determined We previously evaluated the responses to dietary cholesterol in children and young adults . In this study , the effects of dietary cholesterol on plasma lipids and LDL atherogenicity were evaluated in 42 elderly subjects ( 29 postmenopausal women and 13 men > 60 y old ) . Our exclusion criteria were diabetes , heart disease , and the use of reductase inhibitors . The study followed a r and omized crossover design in which subjects were assigned to consume the equivalent of 3 large eggs ( EGG ) daily or the same amount of a cholesterol-free , fat-free egg substitute ( SUB ) for a 1-mo period . After a 3-wk washout period , subjects were assigned to the alternate treatment . The concentration of plasma cholesterol after the EGG period varied among subjects . When all subjects were evaluated , there were significant increases in LDL cholesterol ( LDL-C ) ( P < 0.05 ) and HDL-C ( P < 0.001 ) for both men and women during the EGG period , result ing in no alterations in the LDL-C : HDL-C or the total cholesterol : HDL-C ratios . In addition , the LDL peak diameter was increased during the EGG period for all subjects . In contrast , the measured parameters of LDL oxidation , conjugated diene formation , and LDL lag time did not differ between the EGG and the SUB periods . We conclude from this study that dietary cholesterol provided by eggs does not increase the risk for heart disease in a healthy elderly population In a controlled feeding situation , male subjects were assigned to one of four treatment groups : low fat ( 31 % of total kcal)/low cholesterol ( 193 mg/d ) ( LFLC ) , low fat/usual cholesterol ( 504 mg/d ) ( LFUC ) , usual fat ( 46 % of total kcal)/low cholesterol ( UFLC ) and usual fat/usual cholesterol ( UFUC ) intake . For the first 2 wk of the 10-wk study all subjects consumed the UFUC diet . Subjects consumed experimental diets during wk 3 - 7 and resumed their customary intake during wk 8 - 10 . Plasma total , high-density-lipoprotein ( HDL ) , low-density-lipoprotein and very-low-density-lipoprotein cholesterol and triglycerides were determined weekly . A significant effect ( P less than 0.05 ) of dietary fat on plasma total and HDL cholesterol was observed between the end of wk 2 and 7 .  Low fat intake result ed in 17 + /- 2 mg/dL lower total cholesterol and 10 + /- 1 mg/dL lower HDL cholesterol than the usual fat intake . Plasma lipids were not affected either by dietary cholesterol or by any interaction of dietary fat with cholesterol Carbohydrate-restricted diets ( CRD ) significantly decrease body weight and independently improve plasma triglycerides ( TG ) and HDL cholesterol ( HDL-C ) . Increasing intake of dietary cholesterol from eggs in the context of a low-fat diet maintains the LDL cholesterol (LDL-C)/HDL-C for both hyper- and hypo-responders to dietary cholesterol . In this study , 28 overweight/obese male subjects ( BMI = 25 - 37 kg/m2 ) aged 40 - 70 y were recruited to evaluate the contribution of dietary cholesterol from eggs in a CRD . Subjects were counseled to consume a CRD ( 10 - 15 % energy from carbohydrate ) and they were r and omly allocated to the EGG group [ intake of 3 eggs per day ( 640 mg/d additional dietary cholesterol ) ] or SUB group [ equivalent amount of egg substitute ( 0 dietary cholesterol ) per day ] . Energy intake decreased in both groups from 10,243 + /- 4040 to 7968 + /- 2401 kJ ( P < 0.05 ) compared with baseline . All subjects irrespective of their assigned group had reduced body weight and waist circumference ( P < 0.0001 ) . Similarly , the plasma TG concentration was reduced from 1.34 + /- 0.66 to 0.83 + /- 0.30 mmol/L after 12 wk ( P < 0.001 ) in all subjects . The plasma LDL-C concentration , as well as the LDL-C : HDL-C ratio , did not change during the intervention . In contrast , plasma HDL-C concentration increased in the EGG group from 1.23 + /- 0.39 to 1.47 + /- 0.38 mmol/L ( P < 0.01 ) , whereas HDL-C did not change in the SUB group . Plasma glucose concentrations in fasting subjects did not change . Eighteen subjects were classified as having the metabolic syndrome ( MetS ) at the beginning of the study , whereas 3 subjects had that classification at the end . These results suggest that including eggs in a CRD results in increased HDL-C while decreasing the risk factors associated with A double-blind , cross-over study of the effects of adding cholesterol to the diet , equal to about two egg yolks daily , was carried out in 25 men with an average plasma cholesterol of 5.3 mmol/L. There were no significant elevations in the mean plasma concentrations of cholesterol , low-density-lipoprotein cholesterol , or apolipoprotein B. The absence of an effect was seen against two background diets , one high in saturated fatty acids and the other modified in fat content and in fatty acid composition . Although the mean high-density-lipoprotein ( HDL ) cholesterol concentration did not change , the proportion of HDL2 particles ( radius greater than 4.4 nm ) increased significantly , especially in subjects who did not show a rise in plasma cholesterol ; this may represent a means of clearing dietary cholesterol . The results suggest that reducing dietary cholesterol might be emphasized for hypercholesterolemic subjects rather than for the population generally The plasma total cholesterol ( TC ) and lipoprotein cholesterol concentrations of sedentary young men ( n = 23 ) were determined during 4 wk of controlled feeding and 6 wk of supervised aerobic conditioning . Subjects were assigned to dietary treatments of 400 mg cholesterol per day ( M ) or 1400 mg cholesterol per day ( H ) ; both diets had a P/S ratio of about 0.6 . Dietary groups M and H were subdivided into exercise ( MX and HX ) and sedentary ( MS and HS ) groups . Compared to the sedentary groups , MX and HX exhibited significant ( p less than 0.01 ) improvements in cardiorespiratory fitness . After 2 and 4 wk of high cholesterol feeding , group HS exhibited significant ( p less than 0.05 ) elevations in TC ( + 30 + /- 7 and + 32 + /- 9 mg/dl ) with nonsignificant increases in very low-density lipoprotein cholesterol and low-density lipoprotein cholesterol . Group HX exhibited consistent weekly increases in high-density lipoprotein cholesterol ( HDL-C ) ( from 46 + /- 3 mg/dl , the base level , to 53 + /- 4 mg/dl at wk 4 ) with aerobic conditioning . By combining exercise and sedentary group data at each level of dietary cholesterol it was shown that TC and HDL-C levels significantly ( p less than 0.05 ) increased by the 4th wk of high cholesterol feeding . The TC/HDL-C ratio significantly ( p less than 0.05 ) increased for the sedentary subjects as compared to all the exercising subjects by wk 4 of controlled feeding BACKGROUND Metabolic studies suggest that saturated fatty acids differ in their effects on blood lipids . OBJECTIVE The objective was to examine the associations between intakes of individual saturated fatty acids and their food sources in relation to the risk of coronary heart disease ( CHD ) .  DESIGN This was a prospect i ve cohort study of 80082 women in the Nurses ' Health Study aged 34 - 59 y. Subjects had no known cardiovascular disease , cancer , hypercholesterolemia , or diabetes , and completed vali date d food-frequency question naires in 1980 . RESULTS During 14 y of follow-up , we documented 939 incident cases of major CHD events . In multivariate analyses in which age , smoking , and other covariates were controlled for , intakes of short- to medium-chain saturated fatty acids ( 4:0 - 10:0 ) were not significantly associated with the risk of CHD . In contrast , intakes of longer-chain saturated fatty acids ( 1 
    Output:
    
Increases in LDL cholesterol were no longer statistically significant when intervention doses exceeded 900 mg/d .
Dietary cholesterol did not statistically significantly change serum triglycerides or very-low-density lipoprotein concentrations .
CONCLUSION Review ed studies were heterogeneous and lacked the method ologic rigor to draw any conclusions regarding the effects of dietary cholesterol on CVD risk .
Carefully adjusted and well-conducted cohort studies would be useful to identify the relative effects of dietary cholesterol on CVD risk