You will be presented with a collection of medical randomized controlled trial (RCT) reports addressing a shared clinical question -- for instance, the efficacy of a medical intervention on a disease or condition. Given the titles and abstracts of these reports, your task is to generate the conclusion of the systematic review article synthesizing the key findings. Your conclusion should be a few sentences long. In your response, include only the conclusion and no other text. The RCT reports are below.



Title 1:
Test of Effect of Lipid Lowering by Diet on Cardiovascular Risk: The Minnesota Coronary Survey
Abstract 1:
The Minnesota Coronary Survey was a 4.5-year , open enrollment , single end-time , double-blind , r and omized clinical trial that was conducted In six Minnesota state mental hospitals and one nursing home . It Involved 4393 Institutionalized men and 4664 Institutionalized women . The trial compared the effects of a 39 % fat control diet ( 18 % saturated fat , 5 % polyunsaturated fat , 16 % monounsaturated fat , 446 mg dietary cholesterol per day ) with a 38 % fat treatment diet ( 9 % saturated fat , 15 % polyunsaturated fat , 14 % monounsaturated fat , 166 mg dietary cholesterol per day ) on serum cholesterol levels and the Incidence of myocardlal Infa rct ions , sudden deaths , and all-cause mortality . The mean duration of time on the diets was 384 days , with 1568 subjects consuming the diet for over 2 years . The mean serum cholesterol level In the pre-admission period was 207 mg/dl , falling to 175 mg/dl in the treatment group and 203 mg/dl In the control group . For the entire study population , no differences between the treatment and control groups were observed for cardiovascular events , cardiovascular deaths , or total mortality . A favorable trend for all these end-points occurred In some younger age groups


Title 2:
Circulating and Dietary Omega‐3 and Omega‐6 Polyunsaturated Fatty Acids and Incidence of CVD in the Multi‐Ethnic Study of Atherosclerosis
Abstract 2:
Background Dietary guidelines support intake of polyunsaturated fatty acids ( PUFAs ) in fish and vegetable oils . However , some controversy remains about benefits of PUFAs , and most prior studies have relied on self‐reported dietary assessment in relatively homogeneous population s. Methods and Results In a multiethnic cohort of 2837 US adults ( whites , Hispanics , African Americans , Chinese Americans ) , plasma phospholipid PUFAs were measured at baseline ( 2000–2002 ) using gas chromatography and dietary PUFAs estimated using a food frequency question naire .  Incident cardiovascular disease ( CVD ) events ( including coronary heart disease and stroke ; n=189 ) were prospect ively identified through 2010 during 19 778 person‐years of follow‐up . In multivariable‐adjusted Cox models , circulating n‐3 eicosapentaenoic acid and docosahexaenoic acid were inversely associated with incident CVD , with extreme‐quartile hazard ratios ( 95 % CIs ) of 0.49 for eicosapentaenoic acid ( 0.30 to 0.79 ; Ptrend=0.01 ) and 0.39 for docosahexaenoic acid ( 0.22 to 0.67 ; Ptrend<0.001 ) . n‐3 Docosapentaenoic acid ( DPA ) was inversely associated with CVD in whites and Chinese , but not in other race/ethnicities ( P‐interaction=0.01 ) . No significant associations with CVD were observed for circulating n‐3 alpha‐linolenic acid or n‐6 PUFA ( linoleic acid , arachidonic acid ) . Associations with CVD of self‐reported dietary PUFA were consistent with those of the PUFA biomarkers . All associations were similar across racial‐ethnic groups , except those of docosapentaenoic acid . Conclusions Both dietary and circulating eicosapentaenoic acid and docosahexaenoic acid , but not alpha‐linolenic acid or n‐6 PUFA , were inversely associated with CVD incidence . These findings suggest that increased consumption of n‐3 PUFA from seafood may prevent CVD development in a multiethnic population


Title 3:
Targeted alteration of dietary n-3 and n-6 fatty acids for the treatment of chronic headaches: A randomized trial
Abstract 3:
Summary A dietary intervention increasing n‐3 and reducing n‐6 fatty acids reduced headache pain , altered antinociceptive lipid mediators , and improved quality of life in a chronic headache population . Abstract Omega‐3 and n‐6 fatty acids are biosynthetic precursors to lipid mediators with antinociceptive and pronociceptive properties . We conducted a r and omized , single‐blinded , parallel‐group clinical trial to assess clinical and biochemical effects of targeted alteration in dietary n‐3 and n‐6 fatty acids for treatment of chronic headaches . After a 4‐week preintervention phase , ambulatory patients with chronic daily headache undergoing usual care were r and omized to 1 of 2 intensive , food‐based 12‐week dietary interventions : a high n‐3 plus low n‐6 ( H3‐L6 ) intervention , or a low n‐6 ( L6 ) intervention . Clinical outcomes included the Headache Impact Test ( HIT‐6 , primary clinical outcome ) , Headache Days per month , and Headache Hours per day . Biochemical outcomes included the erythrocyte n‐6 in highly unsaturated fatty acids ( HUFA ) score ( primary biochemical outcome ) and bioactive n‐3 and n‐6 derivatives . Fifty‐six of 67 patients completed the intervention . Both groups achieved targeted intakes of n‐3 and n‐6 fatty acids . In intention‐to‐treat analysis , the H3‐L6 intervention produced significantly greater improvement in the HIT‐6 score ( −7.5 vs −2.1 ; P < 0.001 ) and the number of Headache Days per month ( −8.8 vs −4.0 ; P = 0.02 ) , compared to the L6 group . The H3‐L6 intervention also produced significantly greater reductions in Headache Hours per day ( −4.6 vs −1.2 ; P = 0.01 ) and the n‐6 in HUFA score ( −21.0 vs −4.0 % ; P < 0.001 ) , and greater increases in antinociceptive n‐3 pathway markers 18‐hydroxy‐eicosapentaenoic acid ( + 118.4 vs + 61.1 % ; P < 0.001 ) and 17‐hydroxy‐docosahexaenoic acid ( + 170.2 vs + 27.2 ; P < 0.001 ) . A dietary intervention increasing n‐3 and reducing n‐6 fatty acids  reduced headache pain , altered antinociceptive lipid mediators , and improved quality ‐of‐life in this population


Title 4:
Effect of partial ileal bypass surgery on mortality and morbidity from coronary heart disease in patients with hypercholesterolemia. Report of the Program on the Surgical Control of the Hyperlipidemias (POSCH)
Abstract 4:
BACKGROUND AND METHODS The Program on the Surgical Control of the Hyperlipidemias ( POSCH ) , a r and omized clinical trial , was design ed to test whether cholesterol lowering induced by the partial ileal bypass operation would favorably affect overall mortality or mortality due to coronary heart disease . The study population consisted of 838 patients ( 417 in the control group and 421 in the surgery group ) , both men ( 90.7 percent ) and women , with an average age of 51 years , who had survived a first myocardial infa rct ion . The mean follow-up period was 9.7 years . RESULTS When compared with the control group at five years , the surgery group had a total plasma cholesterol level 23.3 percent lower ( 4.71 + /- 0.91 vs. 6.14 + /- 0.89 mmol per liter [ mean + /- SD ] ; P less than 0.0001 ) , a low-density lipoprotein cholesterol level 37.7 percent lower ( 2.68 + /- 0.78 vs. 4.30 + /- 0.89 mmol per liter ; P less than 0.0001 ) , and a high-density lipoprotein cholesterol level 4.3 percent higher ( 1.08 + /- 0.26 vs. 1.04 + /- 0.25 mmol per liter ; P = 0.02 ) . Overall mortality and mortality due to coronary heart disease were reduced , but not significantly so ( deaths overall [ control vs. surgery ] , 62 vs. 49 , P = 0.164 ; deaths due to coronary disease , 44 vs. 32 , P = 0.113 ) . The overall mortality in the surgery subgroup with an ejection fraction greater than or equal to 50 percent was 36 percent lower ( control vs. surgery , 39 vs. 24 ; P = 0.021 ) . The value for two end points combined -- death due to coronary heart disease and confirmed nonfatal myocardial infa rct ion -- was 35 percent lower in the surgery group ( 125 vs. 82 events ; P less than 0.001 ) . During follow-up , 137 control-group and 52 surgery-group patients underwent coronary-artery bypass grafting ( P less than 0.0001 ) . A comparison of base-line coronary arteriograms with those obtained at 3 , 5 , 7 , and 10 years consistently showed less disease progression in the surgery group ( P less than 0.001 ) . The most common side effect of partial ileal bypass was diarrhea ; others included occasional kidney stones , gallstones , and intestinal obstruction . CONCLUSIONS Partial ileal bypass produces sustained improvement in the blood lipid patterns of patients who have had a myocardial infa rct ion and reduces their subsequent morbidity due to coronary heart disease . The role of this procedure in the management of hypercholesterolemia remains to be determined . These results provide strong evidence supporting the beneficial effects of lipid modification in the reduction of atherosclerosis progression
Kaplan Meier graphs showed no mortality benefit for the intervention group in the full r and omized cohort or for any prespecified subgroup .
Conclusions Available evidence from r and omized controlled trials shows that replacement of saturated fat in the diet with linoleic acid effectively lowers serum cholesterol but does not support the hypothesis that this translates to a lower risk of death from coronary heart disease or all causes .
Findings from the Minnesota Coronary Experiment add to growing evidence that incomplete publication has contributed to overestimation of the benefits of replacing saturated fat with vegetable oils rich in linoleic acid