Effects of dietary manipulation on vascular status of patients with peripheral vascular disease

The impact of nutrition on the development and progression of peripheral artery disease: A systematic review

BACKGROUND & AIMS

This systematic review sought to identify and summarize existing evidence for the impact of nutrition on the development, progression, and outcomes of peripheral artery disease (PAD).

METHODS

We performed a systematic literature search of available studies published between January 1974 and December 2019. Randomized controlled trials (RCT), observational studies, and cross-sectional studies reporting either the primary or secondary prevention of PAD with nutritional intake were included. The quality assessment was performed for the RCTs, without pooling a meta-risk estimate.

RESULTS

Among a total of 8502 records screened, 186 full texts were assessed for eligibility, and 82 studies (30% RCT) were analyzed. The nutrients were structured in fruits, vegetables and antioxidants, fats and oils, dietary fiber, meat, proteins, vitamins and trace elements, and diets and lifestyle. The findings of the current systematic review indicate that the Mediterranean diet, nuts, and polyunsaturated fat are associated with a lower incidence of PAD and saturated fat, cholesterol, and processed meat were associated with higher rates of cardiovascular events in patients suffering from PAD.

CONCLUSIONS

The current review found evidence of a beneficial impact of the Mediterranean diet including nuts in this target population. More RCTs and high-quality registries are needed that focus on nutritional habits among patients with PAD to design appropriate preventive programs.

Low-fat diets for acquired hypercholesterolaemia

BACKGROUND

Hypercholesterolaemia, characterised by raised blood cholesterol levels, is not a disease itself but a metabolic derangement that often contributes to many diseases, notably cardiovascular disease. In most cases, elevated cholesterol levels are associated with high-fat diet, especially saturated fat, coupled with an inactive lifestyle. Less commonly, raised cholesterol may be related to an inherited disorder, familial hypercholesterolaemia. This systematic review is only concerned with acquired hypercholesterolaemia.

OBJECTIVES

To assess the effects of low-fat diets for acquired hypercholesterolaemia and to investigate the incidence of adverse effects from low-fat dietary interventions. We planned to compare the relative effectiveness of low-fat diets with calorie-restricted diets for acquired hypercholesterolaemia. We also wanted to look into the relative effectiveness of low-fat diets and pharmacological interventions for acquired hypercholesterolaemia.

SEARCH STRATEGY

Studies were obtained from computerised searches of The Cochrane Library, MEDLINE, EMBASE and databases of ongoing trials. Date of last search was February 2010.

SELECTION CRITERIA

Otherwise healthy adults (equal to or greater than 18 years) with acquired (not familial) hypercholesterolaemia. We defined hypercholesterolaemia as either total cholesterol greater than 5.2 mmol/L, LDL-cholesterol greater than 3.0 mmol/L, HDL-cholesterol less than 1.0 mmol/L or a combination thereof, although investigators' definitions were also accepted. We wanted to include any low-fat dietary intervention, like low-fat and low-saturated fat diets, intended to lower serum total and LDL-cholesterol or to raise HDL-cholesterol. A low-fat diet was considered as a fat calorie intake less than 20% of the total calories. The minimum duration of the intervention had to be six months. We excluded studies in unhealthy people.

DATA COLLECTION AND ANALYSIS

Two authors were planned to independently assess risk of bias and extract data.

MAIN RESULTS

No study met our inclusion criteria.

AUTHORS' CONCLUSIONS

Well designed, adequately powered randomised controlled trials investigating patient-relevant outcomes of low-fat diets for otherwise healthy people with hypercholesterolaemia are required.

Lipid-lowering for peripheral arterial disease of the lower limb

BACKGROUND

Lipid-lowering therapy is recommended for secondary prevention in people with coronary artery disease. It may also reduce cardiovascular events and/or local disease progression in people with lower limb peripheral arterial disease (PAD).

OBJECTIVES

To assess the effects of lipid-lowering therapy on all-cause mortality, cardiovascular events and local disease progression in patients with PAD of the lower limb.

SEARCH STRATEGY

The authors searched The Cochrane Peripheral Vascular Diseases Group's Specialised Register (last searched February 2007) and the Cochrane Central Register of Controlled Trials (CENTRAL) (last searched Issue 2, 2007) for publications describing randomised controlled trials of lipid-lowering therapy in peripheral arterial disease of the lower limb.

SELECTION CRITERIA

Randomised controlled trials of lipid-lowering therapy in patients with PAD of the lower limb.

DATA COLLECTION AND ANALYSIS

Three authors independently assessed trial quality and extracted data.

MAIN RESULTS

Eighteen trials were included, involving a total of 10,049 participants. Trials differed considerably in their inclusion criteria, outcomes measured, and type of lipid-lowering therapy used. Only one trial (PQRST) reported a detrimental effect of active treatment on blood lipid/lipoprotein levels. The pooled results from all eligible trials indicated that lipid-lowering therapy had no statistically significant effect on overall mortality (Odds Ratio (OR) 0.86; 95% Confidence Interval (CI) 0.49 to 1.50) or on total cardiovascular events (OR 0.8; 95% CI 0.59 to 1.09). However, subgroup analysis which excluded PQRST showed that lipid-lowering therapy significantly reduced the risk of total cardiovascular events (OR 0.74; CI 0.55 to 0.98). This was primarily due to a positive effect on total coronary events (OR 0.76; 95% CI 0.67 to 0.87). Greatest evidence of effectiveness came from the use of simvastatin in people with a blood cholesterol >/= 3.5 mmol/litre (HPS). Pooling of the results from several small trials on a range of different lipid-lowering agents indicated an improvement in total walking distance (Weighted Mean Difference (WMD) 152 m; 95% CI 32.11 to 271.88) and pain-free walking distance (WMD 89.76 m; 95% CI 30.05 to 149.47) but no significant impact on ankle brachial index (WMD 0.04; 95% CI -0.01 to 0.09).

AUTHORS' CONCLUSIONS

Lipid-lowering therapy is effective in reducing cardiovascular mortality and morbidity in people with PAD. It may also improve local symptoms. Until further evidence on the relative effectiveness of different lipid-lowering agents is available, use of a statin in people with PAD and a blood cholesterol level >/=3.5 mmol/litre is most indicated.

Effect of short-term Pritikin diet therapy on the metabolic syndrome

The Pritikin Program (Aventura, FL) involves the use of a very-low-fat, low-sodium, high-fiber diet and exercise to decrease the risk of coronary heart disease (CHD). This study evaluated the effect of short-term Pritikin therapy on the metabolic risk factors for CHD in patients with the metabolic syndrome. Sixty-seven subjects who had the metabolic syndrome and attended the Pritikin Longevity Center & Spa for 12-15 days were studied. Short-term Pritikin therapy improved most CHD risk factors: body mass index decreased by 3% (P<.001); systolic and diastolic blood pressure, and serum glucose and low-density lipoprotein cholesterol concentrations decreased by 10%-15% (P<.001); serum triglyceride concentration decreased by 36% (P<.001); and 37% of subjects no longer met National Cholesterol Education Program criteria for the metabolic syndrome. Serum high-density lipoprotein cholesterol, however, decreased by 3% (P<.05). These data demonstrate that brief treatment with a very-low-fat, low-sodium, high-fiber diet and regular exercise simultaneously improves multiple CHD risk factors in patients with the metabolic syndrome.

Lipid-lowering for lower limb atherosclerosis

BACKGROUND

Raised lipid levels, including cholesterol, are important risk factors in the development of lower limb arterial disease (atherosclerosis).

OBJECTIVES

The objective of this review was to assess the effects of lipid lowering therapy in patients with lower limb atherosclerosis.

SEARCH STRATEGY

The reviewers searched the Cochrane Peripheral Vascular Diseases Group trials register, Embase, reference lists of relevant articles, and contacted trial investigators in Europe and pharmaceutical companies.

SELECTION CRITERIA

Randomised trials of lipid-lowering therapy in patients with lower limb atherosclerosis. The main outcomes were mortality, non-fatal events, direct tests of disease progression, indirect measurements of disease, and subjective measures.

DATA COLLECTION AND ANALYSIS

Two reviewers extracted data and assessed trial quality independently. The reviewers contacted investigators to obtain information needed for the review that could not be found in published reports.

MAIN RESULTS

There were nine eligible trials, but two were excluded because of poor methodology. The seven remaining trials involved a total of 698 participants from seven different countries. Men and women participated in all but one trial and were generally middle aged to elderly. The follow-up period varied from four months to three years. The overall quality of the included trials was high. The trials were heterogeneous in terms of inclusion criteria, type of drugs used and outcomes measured. Lipid-lowering therapy produced a marked but non-significant reduction in mortality (odds ratio 0.21, 95% confidence interval 0. 03 to 1.17), but little change in non-fatal events (odds ratio 1.21, 95% confidence interval 0.80 to 1.83). In two trials there was a significant overall reduction in disease progression on angiogram (odds ratio 0.47, 95% confidence interval 0.29 to 0.77). The changes in ankle brachial pressure index and walking distance were inconsistent, although trials showed a general improvement in symptoms that could not be combined in a meta-analysis. Side effects were generally mild, with the exceptions of liver toxicity produced by betapyridil and the adverse effect of probucol on lipoprotein profile.

REVIEWER'S CONCLUSIONS

Lipid-lowering therapy may be useful in preventing deterioration of underlying disease and alleviating symptoms. These results cannot determine whether one lipid-lowering regimen is better than another.

Studies of women eating diets with different fatty acid composition. I. Plasma lipoproteins and steroid excretion

Moderate changes in dietary fat composition have been recommended to improve plasma cholesterol status. Such changes have not been studied extensively in women. This research evaluates plasma lipoprotein and steroid excretion changes in young women who consumed a diet similar to US average consumption in 1974 [40 en% fat, polyunsaturated (P) to saturated fatty acid (S) ratio, P/S = 0.3, US74] or a diet modified to contain 30 en% fat, P/S = 1.0 (MOD). Following a preexperimental period of self-selected diets, young women were fed the diets for 28-day periods in a crossover design with 10 women at the University of Nebraska, Lincoln, and 10 at Iowa State University, Ames. Plasma lipoproteins and steroid excretion were quantitated and the compositions determined. Data were analyzed for race (five Chinese, 14 Caucasians) and for diet carryover effects, as well as for primary diet effects. In the Chinese women, the US74 diet raised total and very-low-density lipoprotein (VLDL) cholesterol compared to prior self-selected or modified diets; in the Caucasian women the MOD diet lowered total, low-density lipoprotein (LDL), and VLDL cholesterol. The diet carryover was evident in total high-density lipoprotein (HDL) and HDL3 cholesterol. Total HDL and HDL3 cholesterol in response to the US74 diet were unchanged from the MOD diet when the US74 diet followed the MOD diet, but were lower than modified when the US74 diet followed self-selected diets. The US74 diet resulted in greater neutral sterol excretion than the MOD diet; this response was more marked in the self-selected, US74, MOD sequence than in the self-selected, MOD, US74 sequence.(ABSTRACT TRUNCATED AT 250 WORDS)

The effectiveness of a low lipid diet and exercise in the management of coronary artery disease

To evaluate the effects of a high complex carbohydrate, low lipid diet on the management of coronary artery disease, we reviewed data on 32 patients, who had participated in a diet and exercise program, and compared the results with 40 patients who had been managed only with exercise. After a follow-up period of 10 to 16 weeks the patients on the diet-exercise program showed significant reduction in body weight (-6 +/- 2 kg mean +/- standard deviation), serum cholesterol (-43 +/- 41 mg/dl), and triglycerides (-51 +/- 70 mg/dl), while patients who were managed only with exercise had no significant changes in weight or serum lipids. Both the diet-exercise and the exercise groups showed significant improvement in working capacity and reduction in resting systolic blood pressure. Patients on the diet-exercise program had significantly less angina (21.9%) occurring on the exercise test after the program compared to before, even though the same double product was reached. Multiple logistic regression analysis of the data for patients with angina on the exercise test demonstrated that the only significant (p = 0.004) contributor for reduction in angina was the dietary intervention. Beta-blocking drugs did not affect the results. Although randomized controlled trials must be run in order to ascertain the significance of this finding, this study strongly suggests that a low lipid, high carbohydrate diet is a useful addition to exercise in the management of patients with coronary disease.