High density lipoproteins unaffected by dietary fat modification

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Randomised controlled trials, both published and unpublished, where a cholesterol-lowering diet in children and adults with familial hypercholesterolaemia has been compared to other forms of dietary treatment or to no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

Coconut fat and serum lipoproteins: effects of partial replacement with unsaturated fats

The aim of the present study was to examine the effect of reducing saturated fat in the diet, or partly replacing it with unsaturated fat, on the serum lipoprotein profile of human subjects. The study had two intervention periods, 8 weeks (phase 1) and 52 weeks (phase 2). In phase 1, total fat was reduced from 31 to 25 % energy (polyunsaturated fatty acids (PUFA):saturated fatty acids (SFA) ratio increased from 0.2 to 0.4) by reducing the quantity of coconut fat (CF) in the diet from 17.8 to 9.3 % energy intake. In phase 2, subjects were randomised to groups A and B. In group A total fat was reduced from 25 to 20 % energy (PUFA:SFA ratio increased from 0.4 to 0.7) by reducing the quantity of CF in the diet from 9.3 to 4.7 % total energy intake. In group B, the saturated fat content in the diet was similar to group A. In addition a test fat (a mixture of soyabean oil and sesame oil, PUFA:monosaturated fatty acids ratio 2) contributed 3.3 % total energy intake and total fat contributed 24 % energy intake (PUFA:SFA ratio increased from 0.7 to 1.1). At the end of phase 1, there was a 7.7 % reduction in cholesterol (95 % CI -3.6, -12.2) and 10.8 % reduction in LDL (95 % CI -4.9, -16.5) and no significant change in HDL and triacylglycerol. At the end of phase 2, the reduction in cholesterol in both groups was only about 4 % (95 % CI -12, 3.2) partly due the concomitant rise in HDL. The reduction in LDL at 52 weeks was significantly higher in group B (group A mean reduction 11 %, 95 % CI -20.1, -2.0 and group B mean reduction 16.2 % 95 % CI -23.5, -8.9). In phase 2, triacylglycerol levels showed a mean reduction of 6.5 % in group 2A and a mean increase of 8.2 % in group 2B. The reduction of saturated fat in the diet is associated with a lipoprotein profile that would be expected to reduce cardiovascular risk. The reduction of dietary saturated fat with partial replacement of unsaturated fat brings about changes in total cholesterol, HDL- and LDL-cholesterol that are associated with a lower cardiovascular risk.

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 monounsaturated rapeseed oil and a polyunsaturated sunflower oil diet on lipoprotein levels in humans

The effects of high oleic acid rapeseed oil compared with polyunsaturated fats on serum lipoprotein levels are largely unknown. Therefore, we fed 30 women and 29 men a baseline diet rich in saturated fat, which was followed by a diet rich in high oleic and low erucic acid rapeseed oil (total energy content of fat, 38%; saturates, 12.4%; monounsaturates, 16%; n-6 polyunsaturates, 6%; and n-3 polyunsaturates, 2%) and one rich in sunflower oil (total energy content of fat, 38%; saturates, 12.7%; monounsaturates, 10%; n-6 polyunsaturates, 13%; and n-3 polyunsaturates, 0%). The oils were incorporated into mixed natural diets that were dispensed in a random order for 3.5 weeks each in a blinded crossover design. The diet composition was confirmed by analysis of duplicate diets. Both test diets reduced serum total cholesterol (TC) and low density lipoprotein (LDL) cholesterol levels from baseline, the monounsaturated rapeseed oil diet more than the polyunsaturated sunflower oil diet (TC: -15% versus -12%, p less than 0.01; LDL cholesterol: -23% versus -17%, p less than 0.01). Very low density lipoprotein (VLDL) cholesterol and total, VLDL, and LDL triglyceride levels were lower during the sunflower oil diet compared with the rapeseed oil diet. Total high density lipoprotein (HDL) cholesterol levels remained unchanged by both diets. The consumption of rapeseed oil resulted in a more favorable HDL2 to LDL cholesterol ratio (0.43 +/- 0.19 versus 0.39 +/- 0.18, p less than 0.01) and an apolipoprotein A-I to B ratio (3.0 +/- 1.4 versus 2.4 +/- 1.6, p less than 0.001) than did the sunflower oil.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of daily consumption of coconut fat and soya-bean fat on plasma lipids and lipoproteins of young normolipidaemic men

The present paper reports the influence on plasma lipids of isoenergetic diets containing 30% of energy as fat, with a polyunsaturated: saturated fat ratio of 4.00 or 0.25, consumed for 8 weeks by twenty-five young normolipidaemic males. Approximately 70% of the fat energy was provided by the test fats: soya-bean fat and coconut fat. During the soya-bean-fat-eating period the total plasma cholesterol level fell significantly compared with baseline values (P less than 0.001) and during the coconut-fat-eating phase total plasma cholesterol level increased significantly compared with the soya-bean-eating period (P less than 0.001). On the soya-bean-fat diet, high-density-lipoprotein (HDL)-cholesterol decreased by 15% (range 6-35%) and plasma triacylglycerols decreased by 25% (range 13-37%). Results of the present study show that even when the proportion of total fat in the diet is low, a high intake of linoleic acid lowers both total plasma cholesterol and HDL-cholesterol, while a high intake of saturated fat elevates both these lipid fractions. Application of regression formulas to the present findings indicates that short-chain saturated fatty acids have a neutral effect on serum cholesterol.

Reduction of plasma cholesterol levels in normal men on an American Heart Association Step 1 diet or a Step 1 diet with added monounsaturated fat

The design of diets to achieve optimal changes in plasma lipid levels is controversial. In a randomized, double-blind trial involving 36 healthy young men, we evaluated the effects on plasma lipid levels of both an American Heart Association Step 1 diet (in which 30 percent of the total calories were consumed as fat: 10 percent saturated, 10 percent monounsaturated, and 10 percent polyunsaturated fats, with 250 mg of cholesterol per day) and a monounsaturated fat-enriched Step 1 diet (with 38 percent of the calories consumed as fat: 10 percent saturated, 18 percent monounsaturated, and 10 percent polyunsaturated fats, with 250 mg of cholesterol per day). The effects of these diets were then compared with those of an average American diet, in which 38 percent of the total calories were consumed as fat: 18 percent saturated, 10 percent monounsaturated, and 10 percent polyunsaturated fats, with 500 mg of cholesterol per day. The men consumed the average American diet for 10 weeks before random assignment to one of the two Step 1 diets or to continuation of the average diet for an additional 10 weeks. Caloric intake was adjusted to maintain a constant body weight. As compared with the mean (+/- SD) change in the plasma total cholesterol level in the group that followed the average American diet throughout the study (-0.05 +/- 0.36 mmol per liter), there were statistically significant reductions (P less than 0.025) in the plasma total cholesterol level in the group on the Step 1 diet (-0.37 +/- 0.27 mmol per liter) and in the group on the monounsaturated fat-enriched Step 1 diet (-0.46 +/- 0.36 mmol per liter). There were parallel reductions in the plasma low-density lipoprotein cholesterol levels in these two groups. Neither the plasma triglyceride levels nor the high-density lipoprotein cholesterol concentrations changed significantly with any diet. We conclude that enrichment of the Step 1 diet with monounsaturated fat does not alter the beneficial effects of the Step 1 diet on plasma lipid concentrations.

Long-term effects of a linoleic acid-enriched diet, changes in body weight and alcohol consumption on serum total and HDL-cholesterol

Investigations on diet, body weight, and lipoproteins were carried out in 28 patients with stable angina pectoris. They consumed a linoleic acid-enriched diet (P/S ratio = 2) for a period of 2 years. The total fat content remained constant before and during intervention, contributing 34% to energy intake. During intervention serum total cholesterol and the total/HDL cholesterol ratio decreased significantly, but HDL cholesterol did not change. Changes in body weight were significantly inversely related to changes in HDL cholesterol and positively to the total/HDL cholesterol ratio. Changes in alcohol intake were significantly positively related to both total and HDL cholesterol but unrelated to the total/HDL cholesterol ratio. From the results of this long-term study it can be concluded that a moderate fat diet with a P/S ratio of 2 can lower total cholesterol effectively without affecting HDL cholesterol.

Effect of monounsaturated fatty acids versus complex carbohydrates on high-density lipoproteins in healthy men and women

The effects of two strictly controlled diets, one rich in complex carbohydrates, the other rich in olive oil, on serum lipids were studied in healthy men and women. Serum cholesterol levels fell on average by 0.44 mmol/l in the carbohydrate group and 0.46 mmol/l in the olive oil group. HDL cholesterol levels fell by 0.19 mmol/l in the carbohydrate group and rose by 0.03 mmol/l in the olive oil group. Serum triglycerides rose by 0.19 mmol/l in the carbohydrate group and fell by 0.06 mmol/l in the olive oil group. The changes in both HDL and triglycerides were larger in men than in women. These results clearly show that the olive-oil-rich diet, unlike the complex-carbohydrate-rich diet, caused a specific fall in non-HDL cholesterol while leaving serum triglyceride levels virtually unchanged.

Changes in the serum lipoprotein pattern induced by two low-fat diets with a different vegetable content in hypercholesterolemic patients

Thirty-two hypercholesterolemic outpatients were treated by a conventional low-fat diet (carbohydrate 56%; fat 25%; vegetable proteins 7%; animal proteins 12% of energy; P/S ratio 1.0). After 1 month T-C decreased by 11%, VLDL-C by 32%, LDL-C by 8%, HDLt-C by 10% and HDL2-C by 11%. Thirty-two comparable patients were treated by a different low-fat diet which provided 69% of energy as carbohydrate, 19% as fat, 7% as vegetable proteins and 5% as animal proteins; P/S ratio was 1.3. After 1 month T-C decreased by 9% and LDL-C by 12%. VLDL-C, HDL2-C and HDL3-C did not change significantly. A cross-over study on 24 patients confirmed that both diets have lowering effects on T-C and LDL-C levels, but only the conventional low-fat diet decreases VLDL-C and HDL2-C.

Influence of polyunsaturated fats and fat restriction on serum lipoproteins in humans

This study was designed to determine the effects of polyunsaturated fats and of reducing intake of total fat on serum lipids, lipoproteins, and apolipoproteins. Twenty-two normolipidemic women living in a nunnery were given a reference diet (fat/carbohydrate 42/46% of energy, P/S ratio 0.16), a polyunsaturated diet (42/46%, P/S 1,0), and a low-fat, polyunsaturated diet (32/56%, P/S 1.0) for 6 weeks each. Serum and lipoprotein lipids were determined by standard procedures, apolipoproteins either by laser immunonephelometry or by rocket immunoelectrophoresis. Consumption of the polyunsaturated diet decreased cholesterol and apolipoprotein B levels in VLDL (-33.1% and -23.8%) and in LDL (-13.5% and -8.8%) without affecting HDL. Consumption of the low-fat, polyunsaturated diet resulted in a reincrease of VLDL triglycerides, but not of VLDL cholesterol. Concentration of VLDL apolipoprotein B further fell (-41.6%) and that of apolipoprotein E decreased (-25.9%), resulting in an increased VLDL lipid/apolipoprotein mass ratio. This study indicates that responses to therapeutic polyunsaturated diet are lowered levels of VLDL and LDL, but unchanged levels of HDL. Additional restriction of dietary fat intake alters the VLDL composition with a decrement in apolipoprotein E enriched VLDL particles.

The effects of exercise and a moderate hypercholesterolemic diet on plasma and hepatic lipoproteins in the rat

Exercise generally has been found to produce beneficial effects on plasma lipid and lipoprotein profiles, but the mechanisms involved and possible dietary interactions have not been well defined. Weanling male Fischer 344 rats were assigned to three groups: normocholesterolemic diet sedentary (NS), hypercholesterolemic diet sedentary (HS), and hypercholesterolemic diet exercised (HE). Exercise consisted of treadmill running at 1.2 to 1.4 km/h at a 9% grade, six days weekly, for a 10-week experimental period. Lipoproteins from plasma and from a recirculating in situ liver perfusion system were then isolated and analyzed. The values of several parameters for HE tended to fall intermediate between HS and NS. Final total plasma cholesterol and liver cholesterol concentrations were significantly different among all three groups (HS greater than HE greater than NS). Plasma HDL-cholesterol and phospholipids and perfusate HDL-cholesterol production rate per gram liver were all significantly lower in HS v NS, with HE lying in between. Plasma HDL protein was lower in HS than in both other groups. Plasma total triglyceride levels were significantly lowered by exercise, but neither plasma nor perfusate VLDL triglyceride levels differed significantly among the three groups. Food intakes of HE and HS rats were similar, but HE rats had significantly lower final body weights. The results suggest that (1) exercise may ameliorate many of the changes in lipoprotein and cholesterol metabolism induced by a diet containing lard and cholesterol, and (2) some of these changes may be mediated by changes in hepatic lipoprotein production.

Effect of a diet low in saturated fatty acids on plasma lipids, lipoproteins, and HDL subfractions

The effect on serum high density lipoprotein subfractions of a low fat diet with a high ratio of polyunsaturated-to-saturated fatty acids was studied in 38 middle-aged volunteers (19 men and 19 women) in North Karelia, Finland. The mean serum HDL2 cholesterol decreased from 32 +/- 2 mg/dl (mean +/- SE) to 28 +/- 2 mg/dl (p less than 0.001) during the experimental diet and returned to 33 +/- 2 mg/dl (p less than 0.001) after a return to the original diet. No changes were observed in the concentration of HDL3 cholesterol. A highly significant decrease was observed in serum apoprotein A-I concentration, but not in apoprotein A-II concentration during the experimental diet. It is concluded that a low-fat, high-P/S ratio diet lowers LDL and HDL2 cholesterol in healthy volunteers, but does not influence the level of HDL3 subfraction.

Changes in very low and low density lipoproteins with dietary fat modification

Since VLDL and LDL are involved in atherogenesis, their response to dietary modification was studied in 15 normal male prisoners. A 3-month reference diet (P/S ratio 0.3, daily cholesterol intake 370 mg) was compared with a modified fat diet (P/S 1.0, 250 mg) given for further 3 months. The decrement in serum cholesterol by 32 mg/dl reflected a decrease in VLDL and LDL. It was associated with a decrease in serum apolipoprotein B by 16 mg/dl and in serum apolipoprotein E by 1.2 mg/dl. The decrement in VLDL cholesterol was paralleled by a lowered VLDL apolipoprotein E content. Serum and VLDL triglycerides, HDL cholesterol and the serum apolipoproteins A-I and A-II did not change significantly. One beneficial result of a conventional dietary regimen is lowered LDL with unaffected HDL. Another effect is the apparent modification of VLDL with a decrement of cholesterol and apolipoprotein E-enriched particles.

[The apolipoproteins in man ]

Twelve different apolipoproteins have been described in human serum. Apo A-I and apo A-II are essential for the structure of the HDL particles and for the function of LCAT activity. Apo B is the main protein in LDL but does also occur in the triglyceride-rich particles. Apo B represents the binding protein for the LDL-receptor pathway. The C-apolipoproteins are located on the surface of VLDL. They are transferred to HDL throughout the catabolism of VLDL and affect lipoprotein lipase activity. This enzyme is also affected by the E-apolipoproteins which occur in the triglyceride-rich particles as well as in HDL. Apo E is the binding site for another specific cell receptor. The concentration and metabolism of apolipoproteins is affected by diet, drugs, hormones, body weight, alcohol, cigarettes, physical exercises, liver and renal diseases. There is a close relation between apolipoproteins and atherosclerosis.