The 5-year experience of modified fat diets on younger men with coronary heart disease

A network analysis of the propagation of evidence regarding the effectiveness of fat-controlled diets in the secondary prevention of coronary heart disease (CHD): Selective citation in reviews

OBJECTIVE

To examine how the first randomised controlled trials (RCTs) evaluating the efficacy of cholesterol-lowering diets in the secondary prevention of coronary heart disease were interpreted in reviews of the literature prior to the National Institutes of Health consensus conference in 1984.

DESIGN

Claim-specific citation network analysis was used to study the network of citations between reviews and RCTs over a defined period (1969-1984). RCTs were identified and classified according to whether their conclusions supported or opposed the use of dietary fat modification/restriction in the secondary prevention of coronary heart disease. Each review published in this period that cited any of the RCTs was classified as supportive, neutral, or unsupportive to the use of dietary fat modification based on a quotation analysis of its evaluation of the findings of these RCTs. Citation bias and underutilisation were detected by applying a comparative density measure, in-degree centrality, and out-degree in a series of sub-graph analyses.

RESULTS

In total, 66 unique publications were identified (four RCTs-one supportive, three unsupportive; 62 reviews-28 supportive, 17 neutral, 17 unsupportive). On average, supportive reviews underutilised the available RCTs to a greater degree than other reviews. Amongst the supportive group, citation bias was common-23 (82%) reviews cited only the one RCT that was supportive.

CONCLUSION

Most reviews that disseminated a supportive evaluation of the results of RCTs in the context of secondary prevention cited only data that supported this position.

Dietary interventions (plant sterols, stanols, omega-3 fatty acids, soy protein and dietary fibers) for familial hypercholesterolaemia

BACKGROUND

A cholesterol-lowering diet and several other dietary interventions have been suggested as a management approach either independently or as an adjuvant to drug therapy in children and adults with familial hypercholesterolaemia (FH). However, a consensus has yet to be reached on the most appropriate dietary treatment. Plant sterols are commonly used in FH although patients may know them by other names like phytosterols or stanols.

OBJECTIVES

To examine whether a cholesterol-lowering diet is more effective in reducing ischaemic heart disease and lowering cholesterol than no dietary intervention in children and adults with familial hypercholesterolaemia. Further, to compare the efficacy of supplementing a cholesterol-lowering diet with either omega-3 fatty acids, soya proteins, plant sterols or plant stanols.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Inborn Errors of Metabolism Trials Register, which is compiled from electronic searches of the Cochrane Central Register of Controlled Trials (CENTRAL) (updated with each new issue of The Cochrane Library), quarterly searches of MEDLINE and the prospective handsearching of one journal - Journal of Inherited Metabolic Disease. Most recent search of the Group's Inborn Errors of Metabolism Trials Register: 22 August 2013. We also searched PubMed to 05 February 2012.

SELECTION CRITERIA

Randomised controlled trials, both published and unpublished, where a cholesterol-lowering diet in children and adults with familial hypercholesterolaemia has been compared to other forms of dietary treatment or to no dietary intervention were included.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the trial eligibility and risk of bias and one extracted the data, with independent verification of data extraction by a colleague.

MAIN RESULTS

In the 2014 update of the review, 15 trials have been included, with a total of 453 participants across seven comparison groups. The included trials had either a low or unclear risk of bias for most of the parameters used for risk assessment. Only short-term outcomes could be assessed due to the short duration of follow up in the included trials. None of the primary outcomes, (incidence of ischaemic heart disease, number of deaths and age at death) were evaluated in any of the included trials. No significant differences were noted for the majority of secondary outcomes for any of the planned comparisons. However, a significant difference was found for the following comparisons and outcomes: for the comparison between plant sterols and cholesterol-lowering diet (in favour of plant sterols), total cholesterol levels, mean difference 0.30 mmol/l (95% confidence interval 0.12 to 0.48); decreased serum LDL cholesterol, mean difference -0.60 mmol/l (95% CI -0.89 to -0.31). Fasting serum HDL cholesterol levels were elevated, mean difference -0.04 mmol/l (95% CI -0.11 to 0.03) and serum triglyceride concentration was reduced, mean difference -0.03 mmol/l (95% CI -0.15 to -0.09), although these changes were not statistically significant. Similarly, guar gum when given as an add on therapy to bezafibrate reduced total cholesterol and LDL levels as compared to bezafibrate alone.

AUTHORS' CONCLUSIONS

No conclusions can be made about the effectiveness of a cholesterol-lowering diet, or any of the other dietary interventions suggested for familial hypercholesterolaemia, for the primary outcomes: evidence and incidence of ischaemic heart disease, number of deaths and age at death,due to the lack of data on these. Large, parallel, randomised controlled trials are needed to investigate the effectiveness of a cholesterol-lowering diet and the addition of omega-3 fatty acids, plant sterols or stanols, soya protein, dietary fibers to a cholesterol-lowering diet.

Dietary fatty acids in the secondary prevention of coronary heart disease: a systematic review, meta-analysis and meta-regression

OBJECTIVE

Previous systematic reviews were not restricted to either primary or secondary prevention trials, this study aimed to investigate the effects of reduced and/or modified fat diets and dietary fatty acids on all-cause mortality, cardiovascular mortality and cardiovascular events in participants with established coronary heart disease.

DESIGN

Systematic review, meta-analysis and univariate/multivariate meta-regression.

ELIGIBILITY AND CRITERIA FOR SELECTING STUDIES

Electronic searches for randomised controlled trials comparing reduced/modified fat diets versus control diets were performed in MEDLINE, EMBASE and the Cochrane Library.

DATA EXTRACTION

Pooled effects were calculated using an inverse-variance random effect meta-analysis. Random effects univariate and multivariate meta-regressions were performed including changes in all types of dietary fatty acids.

RESULTS

Overall, 12 studies enrolling 7150 participants were included in the present systematic review. No significant risk reduction could be observed considering all-cause mortality (relative risk (RR) 0.92, p=0.60; I(2)=59%) and cardiovascular mortality (RR 0.96, p=0.84; I(2)=69%), combined cardiovascular events (RR 0.85, p=0.30; I(2)=75%) and myocardial infarction (RR 0.76, p=0.13; I(2)=55%) comparing modified fat diets versus control diets. This results could be confirmed for the reduced fat versus control diets (RR 0.79, p=0.47; I(2)=0%), (RR 0.93, p=0.66; I(2)=0%), (RR 0.93, p=0.71; I(2)=57%) and (RR 1.18, p=0.26; I(2)=18%). The multivariate and univariate model showed no significant associations between the independent variables and the changes from saturated fat, monounsaturated fat, polyunsaturated fat and linoleic acid. Sensitivity analyses did not reveal a significant risk reduction for any outcome parameter when polyunsaturated fat was increased in exchange for saturated fat.

CONCLUSIONS

The present systematic review provides no evidence (moderate quality evidence) for the beneficial effects of reduced/modified fat diets in the secondary prevention of coronary heart disease. Recommending higher intakes of polyunsaturated fatty acids in replacement of saturated fatty acids was not associated with risk reduction.

Dietary treatment for familial hypercholesterolaemia

BACKGROUND

A cholesterol-lowering diet and several other dietary interventions have been suggested as a management approach either independently or as an adjuvant to drug therapy in children and adults with familial hypercholesterolemia. However, a consensus has yet to be reached on the most appropriate dietary treatment.

OBJECTIVES

To examine whether a cholesterol-lowering diet is more effective in reducing ischaemic heart disease and lowering cholesterol than no dietary intervention in children and adults with familial hypercholesterolaemia. Further, to compare the efficacy of supplementing a cholesterol-lowering diet with either omega-3 fatty acids, soya proteins, plant sterols or plant stanols.

SEARCH STRATEGY

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Inborn Errors of Metabolism Trials Register.Most recent search of the Group's Inborn Errors of Metabolism Trials Register: 09 October 2009.We also searched PubMed till 01 June 2008.

SELECTION CRITERIA

Randomised controlled trials, both published and unpublished, where a cholesterol-lowering diet in children and adults with familial hypercholesterolaemia has been compared to other forms of dietary treatment or to no dietary intervention were included.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the trial eligibility and methodological quality and one extracted the data, with independent verification of data extraction by a colleague.

MAIN RESULTS

In the present update, four new trials have been added making eleven trials with a total of 331 participants eligible for inclusion. Only short-term outcomes could be assessed due to the short duration of follow up in the included studies. None of the primary outcomes, (incidence of ischaemic heart disease, number of deaths and age at death) were evaluated in any of the included studies. No significant difference was noted for the majority of secondary outcomes for any of the planned comparisons. However, a significant difference was found only for the following comparison and outcome: total cholesterol levels for the comparison between plant sterols and cholesterol-lowering diet, mean difference 0.70 (95% confidence interval 0.19 to 1.21).

AUTHORS' CONCLUSIONS

No conclusions can be made about the effectiveness of a cholesterol-lowering diet, or any of the other dietary interventions suggested for familial hypercholesterolaemia, due to the lack of adequate data. Large, parallel, randomised controlled trials are needed to investigate the effectiveness of a cholesterol-lowering diet and the addition of omega-3 fatty acids, plant sterols or stanols, soya protein to a cholesterol-lowering diet.

Omega-3 fatty acids and cardiovascular disease: The epidemiological evidence

Epidemiological studies in the last 40 years suggest that omega-3 fatty acids derived from fish and fish oil decrease the risk of coronary heart disease, hypertension and stroke, and their complications. The beneficial effects of omega-3 fatty acids include effects on lipids, blood pressure, cardiac and vascular function, eicosanoids, coagulation, and immunological responses. However, not all population studies have shown that omega-3 fatty acids are associated with reduced rates of coronary mortality. Such studies suffer either from small numbers of subjects or the population already had a high intake of fish. When comparing the highest intake of fish to that of the lowest fish intake, the beneficial effects of omega-3 fatty acids have been shown. In population-based case-control studies, the patients consuming modest amounts of fish, the equivalent of one fatty fish meal per week, had a significant lower risk of primary cardiac arrest compared with those who did not eat fish at all. In case-control studies, the intake of eicosapentaenoic acid and docosahexaenoic acid as reflected in adipose tissue content is inversely associated with risk of myocardial infarction.

Dietary treatment for familial hypercholesterolaemia

BACKGROUND

Familial hypercholesterolaemia is an inherited disorder characterised by a raised blood cholesterol, the presence of xanthomatosis and premature ischaemic heart disease. The aim of treatment is the reduction of blood LDL cholesterol concentrations in order to reduce the risk of ischaemic heart disease. Current treatment is based on a cholesterol lowering diet alone or in combination with drug therapy. Many of the drugs found to be effective in treating adults with this disease are not licensed for use in children, therefore diet is the main treatment of children with familial hypercholesterolaemia. In addition to the cholesterol-lowering diet, several other dietary interventions have been suggested and consensus has yet to be reached on the most appropriate dietary treatment for children and adults with familial hypercholesterolaemia.

OBJECTIVES

To examine the evidence that in children and adults with familial hypercholesterolaemia, a cholesterol lowering diet is more effective at lowering cholesterol and reducing incidence of ischaemic heart disease than no intervention or than other dietary interventions.

SEARCH STRATEGY

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Trials Register, a specialist trials register which comprises references identified from comprehensive electronic database searches, handsearching relevant journals and handsearching abstract books of conference proceedings. Additional studies were identified from handsearching the Journal of Inherited Metabolic Disease (from inception, 1978 to 2000) and from the reference lists of identified studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs), both published and unpublished, where a cholesterol lowering diet in children and adults with familial hypercholesterolaemia has been compared to other forms of dietary treatment or to no dietary intervention. Trials which include patients with familial hypercholesterolaemia alongside patients with non-familial hypercholesterolaemia were only included if the group of familial patients was well defined and the results for these patients were available.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed the trial eligibility and methodological quality and one reviewer extracted the data, with independent verification of data extraction by a colleague.

MAIN RESULTS

Only short term outcomes could be assessed in this review due to the length of the five eligible studies. Compliance to treatment, quality of life, mortality and evidence of ischaemic or atheromatous disease were not assessed in the studies identified. No differences were found between the cholesterol-lowering diet and all other diets for all of the short term outcomes assessed.

REVIEWER'S CONCLUSIONS

No conclusions can be made about the effectiveness of the cholesterol-lowering diet, or any of the other dietary interventions suggested for familial hypercholesterolaemia, due to the lack of adequate data. A large, parallel, randomised controlled trial is needed to investigate the effectiveness of the cholesterol-lowering diet and other dietary interventions for FH. It is also possible that data from trials including subjects with both familial and non-familial hypercholesterolaemia could alter the results of future updates of this review and until further evidence is available current dietary treatment of FH should continue to be observed and monitored with care.

Effects of a low cholesterol eating plan on plasma lipids: results of a three-year community study

In an attempt to demonstrate whether individuals with average plasma lipids would accept a diet low in saturated fat and cholesterol, members of a community organization were taught the HELP Your Heart Eating Plan. Results of 282 individuals suggest that reduced dietary cholesterol from selected foods could be sustained for up to 36 months. While both plasma cholesterol and triglycerides fell during a year of instruction, both rose to above initial values by 36 months. Overall, the results suggest that adults may be willing to accept a new style of eating temporarily but are not committed to making permanent dietary changes.

The cholesterol problem, the egg and lipid metabolism in the laying hen

There is little doubt that high blood serum lipid levels are related to a higher incidence of atherosclerotic disease in humans. Experimental evidence to date suggests that dietary intervention can reduce blood lipid levels in most cases and that some small reduction in occurrence of cardiovascular disease will probably result. On the other hand no reduction in total mortality has been demonstrated in the well constructed dietary studies. It appears that there is considerable variation in the human population with regard to their patterns of lipid metabolism. Some apparently regulate body production of cholesterol in response to dietary changes, others do not. Some seem to excrete excess sterols efficiently, while some do not. It seems likely, therefore, that dietary manipulation would be useful for those disposed by heredity and other conditions to accumulation of excessive sterols in the body. On the other hand drug control of cholesterol biosynthesis and/or sterol excretion may be more effective solutions to the problem of sterol accumulation. Irrespective of whether diet or drugs prove to be the best answer to control of sterol balance, these should be applied only to that segment of the population known to require such treatment. The egg is an important dietary source of cholesterol and as a result is used sparingly in low cholesterol diets. On the other hand normal egg consumption of two eggs per day does not appear to overload cholesterol balance in the healthy human adult since depression in cholesterol biosynthesis and increased sterol excretion will result. Investigation of the lipid metabolism of the laying hen has shown that most of the cholesterol found in the egg is synthesized in the liver where it is under both dietary and drug control. Most of the cholesterol deposited in egg yolk may be essential for embryonic development. Drugs that severely limit cholesterol biosynthesis probably also limit synthesis of adrenal and sex hormones and hence limit reproduction. Moderate depressions in lipogenesis achieved without feeding of large amounts of dietary fat may offer a means for moderating cholesterol deposition in eggs. On the other hand, it also seems clear that genetic selection could be used to moderate egg cholesterol concentration. In any event, a great deal more evidence from well constructed human diet studies will be needed before low cholesterol diets can be recommended to the general population as an aid to control of cholesterol balance and heart disease.

Study of drugs affecting cholesterol-induced atherosclerosis in rabbits

1. Effects of various drugs on cholesterol-induced atherosclerosis in rabbits during the progression phase have been studied. The drugs tested are antimetabolites (mercaptopurine, hydroxyurea), surface active agents (sodiumdodecyl sulfate), inhibitor of adrenocoritcal steroid synthesis (o, p'-DDD), lysosome stablizers (chloroquine, acetylsalicylic acid) with antihistaminic (chlorpheniramine) and cholesterol binder (nystatin). 2. Mercaptopurine treatment showed marekd reduction in both atherosclerotic lesions and cholesterol concentrations of the serum and aorta. 3. Hydroxyurea reduced both the aortic cholesterol concentration and the lesions, but the serum cholesterol concentration remained high. 4. Sodiumdodecyl sulfate and o, o'-DDD showed slight inhibition of the development of atherosclerosis. 5. Pyridinocarbamate showed a slight beneficial effect on the prevention of atherosclerosis only when it was administered prior to the meal. 6. Nystatin, chloroquine and acetylsalicylic acid + chlorpheniramine showed little effect.