Cholesterol-lowering effects of a new isolated soy protein with high levels of nondenaturated protein in hypercholesterolemic patients

Effects of plant protein and animal protein on lipid profile, body weight and body mass index on patients with hypercholesterolemia: a systematic review and meta-analysis

OBJECTIVE

We conducted a meta-analysis on the effect of plant protein or animal protein on body weight (BW), body mass index (BMI) and blood lipid profiles in patients with hypercholesterolemia.

MATERIALS AND METHODS

We used subject and free words to search PubMed, Embase and Cochrane Library databases. The risk-of-bias evaluation tool was used to assess literature quality. Data merging and statistical analyses were carried out using Review Manager 5.3 and Stata 13.0. All indicators were expressed as the mean difference (MD) and 95% confidence interval (95% CI). The heterogeneity test was conducted according to I² and Q tests. We used Egger's test to evaluate publication bias quantitatively.

RESULTS

This was a meta-analysis of intervention trials. Thirty-two studies (1562 patients) were included. The quality of the included studies was acceptable. Compared with consumption of animal protein, plant protein reduced total cholesterol (TC) (MD = - 0.19 mmol/L, 95% CI - 0.26, - 0.12), triglyceride (MD = - 0.07 mmol/L, 95% CI - 0.13, - 0.02), low-density lipoprotein cholesterol (LDL-C) (MD = - 0.19 mmol/L, 95% CI - 0.26, - 0.13), very low-density lipoprotein cholesterol (MD = - 0.05 mmol/L, 95% CI - 0.09, - 0.01), TC/LDL-C ratio (MD = - 0.17, 95% CI - 0.32, - 0.02) and LDL-C/HDL-C ratio (MD = - 0.20, 95% CI - 0.33, - 0.06) significantly and increased high-density lipoprotein cholesterol (HDL-C) (MD = 0.03 mmol/L, 95% CI 0.01, 0.06) levels, but had no effect on BW (MD = - 0.41 kg, 95% CI - 2.14, 1.33) or BMI (MD = 0.11 kg/m², 95% CI - 0.51, 0.73).

CONCLUSION

Compared with animal protein, consumption of plant protein could improve lipid profile in patients with hypercholesterolemia.

Analysis of Flavonoid Metabolites in Chaenomeles Petals Using UPLC-ESI-MS/MS

Chaenomeles species are used for both ornamental decoration and medicinal purposes. In order to have a better understanding of the flavonoid profile of Chaenomeles, the petals of four Chaenomeles species, including Chaenomeles japonica (RB), Chaenomeles speciose (ZP), Chaenomeles sinensis (GP), and Chaenomeles cathayensis (MY), were selected as experimental material. The total flavonoid content of GP was found to be the highest, followed by MY, ZP, and RB. In total, 179 flavonoid metabolites (including 49 flavonols, 46 flavonoids, 19 flavone C-glycosides, 17 procyanidins, 15 anthocyanins, 10 flavanols, 10 dihydroflavonoids, 6 isoflavones, 5 dihydroflavonols, and 2 chalcones) were identified by Ultra-Performance Liquid Chromatography-Electrospray Ionization-Tandem Mass Spectrometry. Screening of differential flavonoid metabolites showed that GP had higher levels of metabolites when compared with the other three Chaenomeles species. Annotation and enrichment analysis of flavonoid metabolites revealed that cyanidin 3,5-diglucoside and pelargonidin-3,5-diglucoside anthocyanins are likely responsible for the color differences of the four Chaenomeles petals. Additionally, a large number of flavonoids, flavonols, and isoflavones were enriched in the petals of GP. This study provides new insights into the development and utilization of Chaenomeles petals and provides a basis for future investigations into their utilization.

Postprandial Metabolic Response to Rapeseed Protein in Healthy Subjects

Plant proteins have become increasingly important for ecological reasons. Rapeseed is a novel source of plant proteins with high biological value, but its metabolic impact in humans is largely unknown. A randomized, controlled intervention study including 20 healthy subjects was conducted in a crossover design. All participants received a test meal without additional protein or with 28 g of rapeseed protein isolate or soy protein isolate (control). Venous blood samples were collected over a 360-min period to analyze metabolites; satiety was assessed using a visual analog scale. Postprandial levels of lipids, urea, and amino acids increased following the intake of both protein isolates. The postprandial insulin response was lower after consumption of the rapeseed protein than after intake of the soy protein (p < 0.05), whereas the postmeal responses of glucose, lipids, interleukin-6, minerals, and urea were comparable between the two protein isolates. Interestingly, the rapeseed protein exerted stronger effects on postprandial satiety than the soy protein (p < 0.05). The postmeal metabolism following rapeseed protein intake is comparable with that of soy protein. The favorable effect of rapeseed protein on postprandial insulin and satiety makes it a valuable plant protein for human nutrition.

Cumulative Meta-Analysis of the Soy Effect Over Time

Background

Soy protein foods have attracted attention as useful plant protein foods with mild cholesterol‐lowering effects that are suitable for inclusion in therapeutic diets. But on the basis of the lack of consistency in significant cholesterol reduction by soy in 46 randomized controlled trials, the US Food and Drug Administration (FDA) is reassessing whether the 1999 heart health claim for soy protein should be revoked.

Methods and Results

We have, therefore, performed a cumulative meta‐analysis on the 46 soy trials identified by the FDA to determine if at any time, since the 1999 FDA final rule that established the soy heart health claim, the soy effect on serum cholesterol lost significance. The cumulative meta‐analysis for both total cholesterol and low‐density lipoprotein cholesterol demonstrated preservation of the small, but significant, reductions seen both before and during the subsequent 14 years since the health claim was originally approved. For low‐density lipoprotein cholesterol, the mean reduction in 1999 was −6.3 mg/dL (95% CI, −8.7 to −3.9 mg/dL; P=0.00001) and remained in the range of −4.2 to −6.7 mg/dL (P=0.0006 to P=0.0002, respectively) in the years after 1999. At no time point did the total cholesterol or low‐density lipoprotein cholesterol reductions lose significance or were the differences at individual time points in the cumulative meta‐analysis significantly different from those seen in 1999 when the health claim was approved.

Conclusions

A cumulative meta‐analysis of the data selected by the FDA indicates continued significance of total cholesterol and low‐density lipoprotein cholesterol reduction after soy consumption and supports the rationale behind the original soy FDA heart health claim.

See Editorial Petersen and Kris‐Etherton

A Meta-Analysis of 46 Studies Identified by the FDA Demonstrates that Soy Protein Decreases Circulating LDL and Total Cholesterol Concentrations in Adults

BACKGROUND

Certain plant foods (nuts and soy protein) and food components (viscous fibers and plant sterols) have been permitted by the FDA to carry a heart health claim based on their cholesterol-lowering ability. The FDA is currently considering revoking the heart health claim for soy protein due to a perceived lack of consistent LDL cholesterol reduction in randomized controlled trials.

OBJECTIVE

We performed a meta-analysis of the 46 controlled trials on which the FDA will base its decision to revoke the heart health claim for soy protein.

METHODS

We included the 46 trials on adult men and women, with baseline circulating LDL cholesterol concentrations ranging from 110 to 201 mg/dL, as identified by the FDA, that studied the effects of soy protein on LDL cholesterol and total cholesterol (TC) compared with non-soy protein. Two independent reviewers extracted relevant data. Data were pooled by the generic inverse variance method with a random effects model and expressed as mean differences with 95% CI. Heterogeneity was assessed and quantified.

RESULTS

Of the 46 trials identified by the FDA, 43 provided data for meta-analyses. Of these, 41 provided data for LDL cholesterol, and all 43 provided data for TC. Soy protein at a median dose of 25 g/d during a median follow-up of 6 wk decreased LDL cholesterol by 4.76 mg/dL (95% CI: -6.71, -2.80 mg/dL, P < 0.0001; I2 = 55%, P < 0.0001) and decreased TC by 6.41 mg/dL (95% CI: -9.30, -3.52 mg/dL, P < 0.0001; I2 = 74%, P < 0.0001) compared with non-soy protein controls. There was no dose-response effect or evidence of publication bias for either outcome. Inspection of the individual trial estimates indicated most trials (∼75%) showed a reduction in LDL cholesterol (range: -0.77 to -58.60 mg/dL), although only a minority of these were individually statistically significant.

CONCLUSIONS

Soy protein significantly reduced LDL cholesterol by approximately 3-4% in adults. Our data support the advice given to the general public internationally to increase plant protein intake. This trial was registered at clinicaltrials.gov as NCT03468127.

Isoflavones

Phytoestrogens are naturally occurring nonsteroidal phenolic plant compounds that, due to their molecular structure and size, resemble vertebrate steroids estrogens. This review is focused on plant flavonoids isoflavones, which are ranked among the most estrogenic compounds. The main dietary sources of isoflavones for humans are soybean and soybean products, which contain mainly daidzein and genistein. When they are consumed, they exert estrogenic and/or antiestrogenic effects. Isoflavones are considered chemoprotective and can be used as an alternative therapy for a wide range of hormonal disorders, including several cancer types, namely breast cancer and prostate cancer, cardiovascular diseases, osteoporosis, or menopausal symptoms. On the other hand, isoflavones may also be considered endocrine disruptors with possible negative influences on the state of health in a certain part of the population or on the environment. This review deals with isoflavone classification, structure, and occurrence, with their metabolism, biological, and health effects in humans and animals, and with their utilization and potential risks.

Effect of Plant Protein on Blood Lipids: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

BACKGROUND

There is a heightened interest in plant-based diets for cardiovascular disease prevention. Although plant protein is thought to mediate such prevention through modifying blood lipids, the effect of plant protein in specific substitution for animal protein on blood lipids remains unclear. To assess the effect of this substitution on established lipid targets for cardiovascular risk reduction, we conducted a systematic review and meta-analysis of randomized controlled trials using the Grading of Recommendations Assessment, Development, and Evaluation system.

METHODS AND RESULTS

MEDLINE, EMBASE, and the Cochrane Registry were searched through September 9, 2017. We included randomized controlled trials of ≥3 weeks comparing the effect of plant protein in substitution for animal protein on low-density lipoprotein cholesterol, non-high-density lipoprotein cholesterol, and apolipoprotein B. Two independent reviewers extracted relevant data and assessed risk of bias. Data were pooled by the generic inverse variance method and expressed as mean differences with 95% confidence intervals. Heterogeneity was assessed (Cochran Q statistic) and quantified (I2 statistic). The overall quality (certainty) of the evidence was assessed using the Grading of Recommendations Assessment, Development, and Evaluation system. One-hundred twelve randomized controlled trials met the eligibility criteria. Plant protein in substitution for animal protein decreased low-density lipoprotein cholesterol by 0.16 mmol/L (95% confidence interval, -0.20 to -0.12 mmol/L; P<0.00001; I2=55%; moderate-quality evidence), non-high-density lipoprotein cholesterol by 0.18 mmol/L (95% confidence interval, -0.22 to -0.14 mmol/L; P<0.00001; I2=52%; moderate-quality evidence), and apolipoprotein B by 0.05 g/L (95% confidence interval, -0.06 to -0.03 g/L; P<0.00001; I2=30%; moderate-quality evidence).

CONCLUSIONS

Substitution of plant protein for animal protein decreases the established lipid targets low-density lipoprotein cholesterol, non-high-density lipoprotein cholesterol, and apolipoprotein B. More high-quality randomized trials are needed to improve our estimates.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT02037321.

Current knowledge and future direction of research on soy isoflavones as a therapeutic agents

Isoflavones, the most abundant phytoestrogens in Soy beans, are structurally similar to 17beta-estradiol. The antioxidant property of the soy isoflavones, namely, genistein and daidzein is well established in different experimental models and also in clinical studies. The compounds have been found effective in the management of diabetes by acting on peroxisome proliferator-activated receptors. It reduces the risk of coronary heart disease by reducing the level of low-density lipoprotein and triglycerides. Soy isoflavones have the potential in the treatment of osteoporosis to act on osteoclasts further to inhibit tyrosine kinase. Among the soy isoflavones, genistein is the potential compound found effective in the treatment of cancer by acting on androgen receptor further to inhibit tyrosine kinases. In this article, various aspects of the diverse biological activities of soy isoflavones and their potential clinical implications with mechanism of action, especially in the treatment and prevention of diabetes, cardiovascular diseases, cancer, osteoporosis, neuroprotection, and also future area of research on soy isoflavones are reviewed and discussed.

Soy protein effects on serum lipoproteins: a quality assessment and meta-analysis of randomized, controlled studies

OBJECTIVES

Many randomized controlled trials (RCTs) have assessed the effects of soy protein on serum lipoprotein risk factors for coronary heart disease (CHD). This review and meta-analysis assessed the quality of these RCTs and estimated the effects of soy protein consumption on serum lipoproteins.

DATA SOURCES

A comprehensive search using multiple databases was conducted for the years 1996 through 2008 to identify clinical trials related to soy protein intake and serum lipoprotein changes.

STUDY ELIGIBILITY

RCTs were assessed that met these requirements: soy protein intake compared with nonsoy protein, provided information on serum low-density lipoprotein (LDL)-cholesterol values, provided no more than 65 g of soy protein daily, and obtained LDL-cholesterol measurements between 4 and 18 weeks of treatment. Randomized parallel and crossover studies were evaluated.

METHODS

Studies were graded for quality using 12 criteria with a possible maximum grade of 24. Net changes in lipoproteins with soy protein consumption compared with nonsoy control diets were analyzed by meta-analyses and funnel plots. Confidence intervals were constructed using inverse weighting. Analyses compared parallel to crossover studies and studies with lower and higher grades.

RESULTS

Analyses included 20 parallel-design studies and 23 crossover studies. Parallel studies scored significantly higher (p < 0.001) in study quality, with a mean grade of 15.8 (95% confidence interval [CI], 14.3 to 17.3) compared with 10.1 (95% CI, 8.2 to 11.9) for crossover trials. Soy protein intake was associated with net changes in serum LDL-cholesterol values of -0.23 mmol/l (95% CI, -0.28 to -0.18 mmol/l) or a 5.5% reduction in parallel studies and -0.16 mmol/l (95% CI, -0.22 to -0.11 mmol/l) or a reduction of 4.2% with crossover studies (p < 0.001 for parallel vs crossover). In parallel studies, net serum HDL-cholesterol values were 3.2% higher (p < 0.007) with soy vs control, and fasting serum triacylglycerol values were 10.7% lower (p < 0.008) for soy vs control.

CONCLUSIONS AND IMPLICATIONS

Soy protein consumption with a median of 30 g/d was associated with a significant improvement in lipoprotein risk factors for CHD. Compared with crossover RCTs, parallel RCTs had significantly higher quality grades and were associated with significantly greater improvements in serum LDL-cholesterol values. Regular consumption of 1 to 2 servings of soy protein daily (15 to 30 g) has a significant favorable impact on serum lipoprotein risk factors for CHD.

Systematic review, meta-analysis and regression of randomised controlled trials reporting an association between an intake of circa 25 g soya protein per day and blood cholesterol

AIMS

To determine the effect of a daily intake of circa 25 g soya protein on blood lipids in adults with normal or mildly elevated cholesterolaemia.

METHODS

Medline and other scientific databases were searched to identify randomised controlled trials (RCTs); these were systematically reviewed against pre-determined criteria. Eligible RCTs evaluated the effect of 25 g (range 15-40 g) soya protein on measures of blood lipids. Results from RCTs were pooled using standard meta-analysis methods.

RESULTS

Thirty studies containing 42 treatment arms (n=2913), with an average soya protein intake of 26.9 g met the inclusion criteria. Soya protein inclusion led to reductions in standard difference in mean low density lipoprotein (LDL), total cholesterol and blood triglycerides of 0.23 mmol/L (95% confidence interval (CI) -0.160 to -0.306, p<0.0001), 0.22 mmol/L (95% CI -0.142 to -0.291, p<0.0001) and 0.08 mmol/L (95% CI -0.004 to -0.158, p=0.04), respectively. There was no effect on mean difference in apolipoprotein A (ApoA), but ApoB was reduced by 0.021 g/L (p=0.01) in the soya group. Meta-regression analysis indicated no dose response relationship between soya protein intake in the range of 15-40 g and standard difference in LDL or HDL. All data were tested for heterogeneity and none identified.

CONCLUSIONS

The inclusion of modest amounts soya protein (ca. 25 g) into the diet of adults with normal or mild hypercholesterolaemia resulted in small, highly significant reductions in total and LDL cholesterol, equivalent to ca. 6% LDL reduction. This practically achievable intake, particularly when combined with other dietary measures, can make a useful contribution to blood cholesterol management.