Effects on the serum lipoprotein concentrations by lipid-lowering diets with different fatty acid compositions

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Randomised controlled trials, both published and unpublished, where a cholesterol-lowering diet in children and adults with familial hypercholesterolaemia has been compared to other forms of dietary treatment or to no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

The use of fatty acid biomarkers to reflect dietary intake

PURPOSE OF REVIEW

This review compares fatty acid biomarkers to assess compliance in dietary intervention trials with their application in epidemiological studies.

RECENT FINDINGS

Although many studies have used fatty acid biomarkers to assess compliance in short-term dietary intervention trials and habitual diets in observational studies, there is little information on the reliability and comparability of these measures. In this review, we summarize the usefulness and limitations of fatty acid biomarkers in clinical and epidemiological studies. As there are very few recent publications in this area, a complete literature review is provided.

SUMMARY

Several options are available for the biological assessment of dietary fatty acids. The type of study (short or long-term), the metabolic characteristics and expected variability in the fatty acids of interest are major considerations when determining which tissues reflect a better measure of true intake. Certain fatty acids may not be suitable to assess differences in intake under non-isocaloric conditions and when trying to identify small differences. Serum cholesterol ester is the most suitable serum fraction to assess short-term dietary compliance, but given the multiple factors that affect response, the quantification of compliance should be interpreted with caution. Adipose tissue is the biomarker of choice for long-term intake, but a preferred blood constituent (plasma versus erythrocytes) is difficult to establish given the data available to date. Future studies should explore the use of whole blood as an alternative choice to measure fatty acid intake in epidemiological studies.

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 nicotinic acid treatment on fatty acid composition of plasma lipids and adipose tissue in hyperlipidaemia

Effects of 6-week treatment with 4 g daily of nicotinic acid on fatty acid composition in different serum lipids and in adipose tissue glycerides were studied in 31 hyperlipidemic patients. The percentages of eight fatty acids in triglycerides, phospholipids and cholesteryl esters of whole plasma as well as in subcutaneous adipose tissue glycerides were measured. Nicotinic acid treatment produced decreases in triglyceride and total cholesterol concentrations of VLDL and LDL, whereas HDL total cholesterol levels in serum increased after drug therapy, all p less than 0.01. There were reductions in the relative contents of myristic acid in plasma phospholipids (from 0.4% to 0.3%; p less than 0.05) and cholesteryl esters (from 0.9% to 0.7%; p less than 0.001). There were decreases in the percentages of stearic acid in plasma phospholipids (from 17.0% to 15.0%) and cholesteryl esters (from 1.2% to 1.0%; both p less than 0.001). The relative contents of polyunsaturated fatty acids, mainly linoleic acid, in plasma phospholipids were increased (from 32% to 33.5%; p less than 0.05). There were reductions in the linolenic acid contents of adipose tissue (from 1.5% to 1.1%) and plasma triglycerides (from 1.1% to 0.8%), both p less than 0.05, possibly indicating increased conversion of linolenic acid to prostaglandins. There was no relationship between changes in the percentages of individual fatty acids and changes in triglyceride or total cholesterol levels of whole serum and its VLDL, LDL and HDL fractions.(ABSTRACT TRUNCATED AT 250 WORDS)

High content of dietary linoleic acid does not reduce platelet reactivity in patients with hyperlipoproteinaemia

Seventeen patients with hypertriglyceridaemia were given a lipid-lowering diet with a high P/S-ratio 2.1 during a 3-week period. The very low density lipoprotein triglycerides decreased by 43%, low density lipoprotein cholesterol by 19% and high density lipoprotein cholesterol by 12%. There was a marked increase of linoleic acid (18:2 n-6) in all plasma lipid esters with a concomitant decrease of the saturated and monounsaturated fatty acids. There was a slight increase of the linoleic acid metabolites 18:3 n-6, 20:3 n-6 and 20:4 n-6 in serum triglycerides whereas the fatty acids of the n-3 series decreased in all plasma lipid esters. In the platelets a similar pattern was found with an increase of linoleic acid and its metabolite 22:4 n-6 and a decrease of 18:1 n-9 as well as of the n-3 fatty acids. No significant differences in platelet reactivity was found. However, in a few patients there was an increased platelet aggregation after the diet period. Our results suggest that this diet based on a very high content of linoleic acid may not affect platelet reactivity in a beneficial way. The reason may be an increased turnover of arachidonic acid in the platelets or an imbalance between the n-6 and n-3 series of fatty acids.