Effects of extracted soy isoflavones alone on blood total and LDL cholesterol: Meta-analysis of randomized controlled trials

Physicochemical and Functional Properties of DND358 (A Hypocholesterolemic Soybean) Protein Isolate

The properties and applications of soybean protein isolates (SPIs) have been extensively investigated. In this study, we determined the optimal conditions for the preparation of the DND358 soybean protein isolate (DND358-SPI), assessed its physicochemical and functional properties, and investigated its potential applications in the food industry. According to the results, the highest extraction rate of DND358-SPI was observed when the pH was 9.5, the temperature was 55 °C, the duration was 80 min, and the material-to-liquid ratio was 1:20 (w/v). With regard to the functional properties, the water-holding capacity (WHC) and oil-binding capacity (OBC) of DND358-SPI were higher than those of other varieties, reaching 4.73% and 11.04%, respectively. In addition, the hardness, adhesiveness, chewiness, and resilience of DND358-SPI were higher than those of other varieties, reaching 159.27 g, 186.07 g, 6.78 mj, and 1.88, respectively. These findings indicate that DND358-SPI can reduce cholesterol levels and may be used to produce cholesterol-lowering food products.

Protective effect of isoflavone enriched soy β-conglycinin on osteoporosis in ovariectomized rats

Research shows that the consumption of soybean foods can reduce the incidence rate of bone fractures in women after menopause. The aim of this study was to investigate the effects of different complex of soy β-conglycinin (7S) and isoflavones (7S-ISO) on osteoporosis in ovariectomized rats. All treatments were administrated intragastrically to the groups every afternoon for 3 months. The treatments were administrated at 1 mL·(100 g)^-1 , the animals were given 50 mg·kg^-1 ·d^-1 ISO, and the concentration of protein was about 2 wt. %. The bone mineral density (BMD) and the bone biomechanics results of left tibia' maximum load in the 7S-ISO group is significantly higher than in the ovariectomized group and the 7S group (p < .05). Otherwise, the serum tartrate-resistant acid phosphatase (s-TRACP), serum osteocalcin (s-BGP), and serum estradiol (s-E₂ ) levels in 7S-ISO were all significantly different from the OVX, OVX + casein, and the OVX + 7S group (p < .05). The serum calcium (s-Ca) level was not significantly different among all the groups. 7S-ISO may exhibit moderate estrogenic activities and as compared to 7S and ISO in osteoporosis (OP) of ovariectomized rats. PRACTICAL APPLICATIONS: The effects of soy proteins on the health of females have always been a concern. It has been extensively reported soy 7S globulin (7S) as a type of trimer glycoprotein can depress blood fats. The aim of this study was to investigate the effects of different complex of soy β-conglycinin and isoflavones (ISO), the main storage proteins and polyphenols in soy, on osteoporosis in ovariectomized rats.

Association of dietary isoflavone consumption with subclinical cardiovascular disease in middle-aged and elderly Chinese people

BACKGROUND AND AIMS

The association between isoflavone (ISF) consumption and cardiovascular disease (CVD) remains controversial because of limited evidence. Carotid atherosclerosis is an established indicator of subclinical CVD. The study aimed to investigate the relationship between dietary ISF intake and subclinical CVD in middle-aged and elderly adults.

METHODS AND RESULTS

A total of 873 subjects aged 40-70 years without CVD were enrolled in this cross-sectional study. A restricted cubic spline was used to investigate the association between ISF intake and subclinical CVD risk. The odds ratio (OR) and 95% confidence interval of the risk of subclinical CVD for ISF were estimated by two-segmented logistic regression analysis. In Model 2, there was a non-linear association between ISF intake and the risk of subclinical CVD among women (P_non-linear = 0.002), with an inverse association below the change point. The nadir for the risk of subclinical CVD among women was 7.26 mg/day (energy-adjusted). Below the change point, an increase of 1 mg ISF/day reduced the risk of subclinical CVD by 15%. There was no significant association between ISF intake and subclinical CVD risk above the change point (OR = 1.01 [0.99, 1.04]). ISF intake was not associated with subclinical CVD risk in men (Model 2: P_non-linear = 0.224).

CONCLUSIONS

Below the change point (7.26 mg/day), women with a higher intake of ISF had a significantly lower risk of subclinical CVD. Encouraging the consumption of ISF-rich foods may help to lower CVD risk in middle-aged and elderly women.

TRIAL REGISTRATION

This study is registered at http://www.chictr.org.cn (ChiCTR 1900022445).

A Non-Probiotic Fermented Soy Product Reduces Total and LDL Cholesterol: A Randomized Controlled Crossover Trial

Traditional Asian fermented soy food products are associated with reduced cardiovascular disease risk in prospective studies, but few randomized controlled trials have been conducted in at-risk populations. The aim of this study was to investigate the effect of a commercial non-probiotic fermented soy product on blood lipids in adults with cardiovascular risk biomarkers. In a randomized, crossover, intervention study, 27 men and women (aged 29–75 y) exhibiting at least two risk factors, consumed two packets (12.5 g each) daily of a fermented powdered soy product, or an isoenergic control powder made from germinated brown rice for 12 weeks each. The consumption of the fermented soy product resulted in a significantly greater mean change from baseline (compared to the germinated rice, all p < 0.05) in total cholesterol of −0.23 mmol/L (CI: −0.40, −0.06) compared with 0.14 mmol/L (CI: −0.03, 0.31), respectively; and low density lipoprotein (LDL) cholesterol −0.18 mmol/L (CI: −0.32, −0.04) compared with 0.04 mmol/L (CI: −0.01, 0.018) respectively. This was accompanied by an increase in high density lipoprotein (HDL) cholesterol in the germinated rice group, a decrease in apolipoprotein B (ApoB) in the fermented soy group, and a between-treatment effect in apolipoprotein A1 (ApoA1); however, the ratio of the LDL:HDL and of Apo B:ApoA1 did not differ between the groups. The ratio of total cholesterol:LDL decreased in men in the fermented soy group (p < 0.001). Twenty-four-hour urine collection at the end of each treatment period resulted in an increased excretion expressed as a ratio in μmol/d between treatments of 10.93 (CI: 5.07, 23.54) for daidzein; 1.24 (CI: 1.14, 4.43) for genistein; and, 8.48 (CI: 4.28, 16.80) for glycitein, all p < 0.05. The fermented soy powder consumed by participants in this study without implementing other changes in their typical diets, decreased the total and LDL cholesterol, and may serve as a dietary strategy to manage blood lipids. The trial was registered at ClinicalTrials.gov as NCT03429920.

Comprehensive evaluation of the role of soy and isoflavone supplementation in humans and animals over the past two decades

Soy and soy-based foods are considered healthy, particularly in many Asia-Pacific countries, where soy products have long been consumed. Soy and soy-related products have been found to help prevent the occurrence of cardiovascular diseases and certain types of cancer, such as breast and prostate cancer. These products can also have antioxidative effects that alleviate hot flashes during menopause and bone loss. These biological and therapeutic functions are primarily due to the isoflavones derived from soy, whose structure is similar to the structure of 17-β-oestradiol. Despite the many health benefits for humans and animals, the application of isoflavones remains controversial because of their anti-oestrogenic properties. We focused on general information regarding isoflavones, as well as their structure, function, and application. We summarized evidence showing that dietary or supplemental isoflavones exert protective effects on the health of humans and animals. Based on the literature, we conclude that soy foods and isoflavones may be effective and safe; however, more high-quality trials are needed to fully substantiate their potential use.

Beyond the Cholesterol-Lowering Effect of Soy Protein: A Review of the Effects of Dietary Soy and Its Constituents on Risk Factors for Cardiovascular Disease

The hypocholesterolemic effect of soy is well-documented and this has led to the regulatory approval of a health claim relating soy protein to a reduced risk of cardiovascular disease (CVD). However, soybeans contain additional components, such as isoflavones, lecithins, saponins and fiber that may improve cardiovascular health through independent mechanisms. This review summarizes the evidence on the cardiovascular benefits of non-protein soy components in relation to known CVD risk factors such as hypertension, hyperglycemia, inflammation, and obesity beyond cholesterol lowering. Overall, the available evidence suggests non-protein soy constituents improve markers of cardiovascular health; however, additional carefully designed studies are required to independently elucidate these effects. Further, work is also needed to clarify the role of isoflavone-metabolizing phenotype and gut microbiota composition on biological effect.

Liquid chromatography with absorbance detection and with isotope-dilution mass spectrometry for determination of isoflavones in soy standard reference materials

Two independent analytical approaches, based on liquid chromatography with absorbance detection and liquid chromatography with mass spectrometric detection, have been developed for determination of isoflavones in soy materials. These two methods yield comparable results for a variety of soy-based foods and dietary supplements. Four Standard Reference Materials (SRMs) have been produced by the National Institute of Standards and Technology to assist the food and dietary supplement community in method validation and have been assigned values for isoflavone content using both methods. These SRMs include SRM 3234 Soy Flour, SRM 3236 Soy Protein Isolate, SRM 3237 Soy Protein Concentrate, and SRM 3238 Soy-Containing Solid Oral Dosage Form. A fifth material, SRM 3235 Soy Milk, was evaluated using the methods and found to be inhomogeneous for isoflavones and unsuitable for value assignment. Graphical Abstract Separation of six isoflavone aglycones and glycosides found in Standard Reference Material (SRM) 3236 Soy Protein Isolate.

Therapeutic effects of isoflavones on impaired salivary secretion

Dry mouth, which is characterized by decreased salivation, has a number of causes; the involvement of estrogen has been suggested as symptoms typically develop in middle-aged females. However, there is a lack of consensus regarding the treatment of this condition. Soy isoflavones, a subgroup of flavonoids, are abundantly found in the soy germ. They are thought to exert a number of effects by specifically binding to estrogen receptors due to their structural similarity to estrogen. Recently, soy isoflavones have been found to exert antioxidant effects, ameliorating disorders caused by reactive oxygen/free radicals. Based on these observations, the effects of soybean isoflavones on impaired salivary secretion were studied in patients with dry mouth. Soy isoflavone aglycones were administered at 25 mg per day to 15 subjects with an average age of 67.9 ± 8.0 years for 2 months, and salivary secretion was analyzed. The results showed a significant improvement based on the saliva flow rate and self-completed questionnaire, thus suggesting the usefulness of isoflavones in improving the symptoms of salivary gland hypofunction.

Daidzein supplementation decreases serum triglyceride and uric acid concentrations in hypercholesterolemic adults with the effect on triglycerides being greater in those with the GA compared with the GG genotype of ESR-β RsaI

Daidzein (one of the major isoflavones) can be metabolized to equol in certain individuals. The effects of isoflavones alone and equol status on lipid profiles are still controversial. To evaluate the 6-mo effects of daidzein on cardiovascular risk factors in hypercholesterolemic individuals and the interactions of these effects with equol status and estrogen receptor (ESR) genotypes, we conducted a randomized, double-blind, placebo-controlled trial consisting of 210 hypercholesterolemic adults (40-65 y old). The participants were randomly assigned (177 completed) to consume placebo, 40 mg daidzein (DAI40), or 80 mg daidzein (DAI80) daily for 6 mo. Daidzein decreased serum triglycerides (TGs) by 0.15 ± 0.62 mmol/L (mean ± SD) and 0.24 ± 0.61 mmol/L and decreased serum uric acid by 23 ± 47 μmol/L and 29 ± 44 μmol/L in the DAI40 and DAI80 groups, respectively. These reductions in the DAI40 and DAI80 groups were greater than those in the placebo group (P < 0.05). Other blood lipids, glucose, insulin, or glycated hemoglobin did not significantly change after daidzein treatment. No dose-dependent effects of daidzein were found. The reduction of TGs was influenced by the ESR genotype, with a greater effect observed in participants with the GA genotype compared with those with the GG genotype of ESR-β RsaI. These effects were not influenced by equol status. Six-month supplementation of daidzein significantly decreased TGs and uric acid. ESR-β RsaI genotype, not equol status, influenced daidzein's effects on TGs. Daidzein consumption may be effective to improve cardiovascular risk factors, especially in adults with the GA genotype of ESR-β RsaI. This trial was registered at the Chinese clinical trial registry as ChiCTR-TRC-10001048.

Isoflavones for hypercholesterolaemia in adults

BACKGROUND

Hypercholesterolaemia is a significant risk factor for cardiovascular diseases. Isoflavones may be effective in improving hypercholesterolaemia.

OBJECTIVES

To assess the effects of isoflavones for hypercholesterolaemia.

SEARCH METHODS

We searched the following databases: The Cochrane Library (Issue 9, 2012), MEDLINE, EMBASE, Chinese BioMedical Database and China National Knowledge Infrastructure (all to September 2012).

SELECTION CRITERIA

We considered randomized controlled clinical trials in hypercholesterolaemic participants comparing isoflavones versus placebo, or soy isolated protein added with isoflavones versus soy isolated protein alone.

DATA COLLECTION AND ANALYSIS

Two review authors independently abstracted relevant population and intervention characteristics. We resolved any disagreements through discussion, or if required by a third party. We assessed the risk of bias of trials against key criteria: random sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessment, incomplete outcome data, selective reporting and other sources of bias.

MAIN RESULTS

We included five randomized trials (208 participants, 104 in the intervention group and 104 in the control group). Interventions ranged from three to six months. Four trials reported results in non-Asian populations published in English. One trial reported results in Chinese people published in Chinese. Overall, the risk of bias of included trials was high or unclear. There were no outcome data on death from any cause, morbidity, complications, health-related quality of life and costs. Two trials reported adverse effects, including gastrointestinal discomfort (bloating and constipation) and an increased number of hot flushes. None of the trials found serious adverse events. There was a slight significant effect on triglycerides in favour of isoflavones when compared with placebo (mean difference (MD) -0.46 mmol/L (95% confidence interval (CI) -0.84 to -0.09; P = 0.02; 52 participants; 2 trials). No statistically significant effects on total cholesterol, low-density lipoprotein cholesterol and high-density lipoprotein cholesterol were shown in favour of isoflavones.

AUTHORS' CONCLUSIONS

We found no evidence for effects of isoflavones on patient-important outcomes or lowering of cholesterol levels in people with hypercholesterolaemia. Our findings have to be interpreted with caution due to high or unclear risk of bias in several risk of bias domains, and low number of participants in trials.

Mechanisms underlying the dualistic mode of action of major soy isoflavones in relation to cell proliferation and cancer risks

Isoflavones are phytoestrogens that have been linked to both beneficial as well as adverse effects in relation to cell proliferation and cancer risks. The present article presents an overview of these seemingly contradicting health effects and of mechanisms that could be involved in this dualistic mode of action. One mechanism relates to the different ultimate cellular effects of activation of estrogen receptor (ER) α, promoting cell proliferation, and of ERβ, promoting apoptosis, with the major soy isoflavones genistein and daidzein activating especially ERβ. A second mode of action includes the role of epigenetics, including effects of isoflavones on DNA methylation, histone modification and miRNA expression patterns. The overview presented reveals that we are only at the start of unraveling the complex underlying mode of action for effects of isoflavones, both beneficial or adverse, on cell proliferation and cancer risks. It is evident that whatever model system will be applied, its relevance to human tissues with respect to ERα and ERβ levels, co-repressor and co-activator characteristics as well as its relevance to human exposure regimens, needs to be considered and defined.

Polymorphisms in genes involved in the metabolism and transport of soy isoflavones affect the urinary metabolite profile in premenopausal women following consumption of a commercial soy supplement as a single bolus dose

SCOPE

Genetic variation in relevant enzymes and transporters may contribute to discordant observations concerning health outcomes of dietary isoflavone consumption, so we examined the association of the UGT1A1*28 promoter polymorphism and of other SNPs with isoflavone metabolites in urine.

METHODS AND RESULTS

We genotyped prospectively for polymorphisms in UGT1A1 (UGT1A1*28), LPH (666G>A), CBG (1368T>A), ABCG2 (421C>A), and ABCC2 (1249G>A) to select 100 women (18-50 years) to receive a commercial soy supplement as a single dose and collect all urine over 24 h for analysis by RP-HPLC. We observed large differences in isoflavone recovery (mean 39%, eightfold variation) and metabolites. Glucuronides were the major metabolites (72% of total). UGT1A1*28 was associated only with percentage of glycitein as sulphate (positive; p = 0.046), but excluding five participants with both minor alleles of CBG and ABCG2 uncovered additional associations with percentage of glycitein as glucuronide (negative; p = 0.028), combined isoflavones as sulphate (positive; p = 0.035) and sulphate-to-glucuronide ratio for combined isoflavones (positive; p = 0.036). CBG1368T>A, ABCG2 421C>A, and ABCC2 1249G>A were also associated with differences in isoflavone metabolites in urine.

CONCLUSION

Genetic variation in UGT1A1, CBG, ABCG2, and ABCC2 influences isoflavone metabolism so may affect benefits of dietary consumption.

Food combinations for cholesterol lowering

Reducing elevated LDL-cholesterol is a key public health challenge. There is substantial evidence from randomised controlled trials (RCT) that a number of foods and food components can significantly reduce LDL-cholesterol. Data from RCT have been reviewed to determine whether effects are additive when two or more of these components are consumed together. Typically components, such as plant stanols and sterols, soya protein, β-glucans and tree nuts, when consumed individually at their target rate, reduce LDL-cholesterol by 3-9 %. Improved dietary fat quality, achieved by replacing SFA with unsaturated fat, reduces LDL-cholesterol and can increase HDL-cholesterol, further improving blood lipid profile. It appears that the effect of combining these interventions is largely additive; however, compliance with multiple changes may reduce over time. Food combinations used in ten 'portfolio diet' studies have been reviewed. In clinical efficacy studies of about 1 month where all foods were provided, LDL-cholesterol is reduced by 22-30 %, whereas in community-based studies of >6 months' duration, where dietary advice is the basis of the intervention, reduction in LDL-cholesterol is about 15 %. Inclusion of MUFA into 'portfolio diets' increases HDL-cholesterol, in addition to LDL-cholesterol effects. Compliance with some of these dietary changes can be achieved more easily compared with others. By careful food component selection, appropriate to the individual, the effect of including only two components in the diet with good compliance could be a sustainable 10 % reduction in LDL-cholesterol; this is sufficient to make a substantial impact on cholesterol management and reduce the need for pharmaceutical intervention.

Effect of soy isoflavones on blood pressure: a meta-analysis of randomized controlled trials

BACKGROUND AND AIM

The effect of soy isoflavones on blood pressure is controversial. The objective of this study was to evaluate the effect of dietary soy isoflavones on blood pressure.

METHODS AND RESULTS

Trials were searched in PubMed, the Cochrane Library, Embase and references cited in related reviews and studies. A total of eleven trials were reviewed. Meta-analysis results showed a mean decrease of 2.5 mm Hg (95% CIs, - 5.35 to 0.34 mm Hg; P = 0.08) for systolic blood pressure and 1.5 mm Hg (95% CIs, - 3.09 to 0.17 mm Hg; P = 0.08) for diastolic blood pressure in the soy isoflavones-treated group compared to placebo. Meta-regression and subgroup analyses indicated that blood pressure status was a significant predictor of heterogeneity for the effect of soy isoflavones on blood pressure. Subgroup analysis of hypertensive subjects revealed that a greater blood pressure reduction was identified in the soy isoflavone-treated group compared to placebo (5 trials; SBP: - 5.94, 95% CIs [- 10.55, - 1.34] mm Hg, P = 0.01; DBP: - 3.35, 95% CIs [- 6.52, - 0.19] mm Hg, P = 0.04). In contrast, treatment with soy isoflavones did not lead to a significant reduction in blood pressure in normotensive subjects (6 trials; SBP: 0.29, 95% CIs [- 2.39, 2.97] mm Hg, P = 0.83; DBP: - 0.43, 95% CIs [- 1.66, 0.81] mm Hg, P = 0.50).

CONCLUSION

Soy isoflavones had an effect of lowering blood pressure in hypertensive subjects, but not in normotensive subjects. Larger trials need to be carried out to confirm the present findings.

Chinese herbal medicines for hypercholesterolemia

BACKGROUND

Hypercholesterolemia is an important key contributory factor for ischemic heart disease and is associated with age, high blood pressure, a family history of hypercholesterolemia, and diabetes. Chinese herbal medicines have been used for a long time as lipid-lowering agents.

OBJECTIVES

To assess the effects of Chinese herbal medicines on hypercholesterolemia.

SEARCH STRATEGY

We searched the following databases: The Cochrane Library (issue 8, 2010), MEDLINE (until July 2010), EMBASE (until July 2010 ), Chinese BioMedical Database (until July 2010), Traditional Chinese Medical Literature Analysis and Retrieval System (until July 2010), China National Knowledge Infrastructure (until July 2010), Chinese VIP Information (until July 2010), Chinese Academic Conference Papers Database and Chinese Dissertation Database (until July 2010), and Allied and Complementary Medicine Database (until July 2010).

SELECTION CRITERIA

We considered randomized controlled clinical trials in hypercholesterolemic participants comparing Chinese herbal medicines with placebo, no treatment, and pharmacological or non-pharmacological interventions.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed the risk of bias. We resolved any disagreements with this assessment through discussion and a decision was achieved based by consensus. We assessed trials for the risk of bias against key criteria: random sequence generation, allocation concealment, blinding of participants, incomplete outcome data, selective outcome reporting and other sources of bias.

MAIN RESULTS

We included 22 randomized trials (2130 participants). The mean treatment duration was 2.3 ± 1.3 months (ranging from one to six months). Twenty trials were conducted in China and 18 trials were published in Chinese. Overall, the risk of bias of included trials was high or unclear. Five different herbal medicines were evaluated in the included trials, which compared herbs with conventional medicine in six comparisons (20 trials), or placebo (two trials). There were no outcome data in any of the trials on cardiovascular events and death from any cause. One trial each reported well-being (no significant differences) and economic costs. No serious adverse events were observed. Xuezhikang was the most commonly used herbal formula investigated. A significant effect on total cholesterol (two trial, 254 participants) was shown in favor of Xuezhikang when compared with inositol nicotinate (mean difference (MD) -0.90 mmol/L, 95% confidence interval (CI) -1.13 to -0.68) .

AUTHORS' CONCLUSIONS

Some herbal medicines may have cholesterol-lowering effects. Our findings have to be interpreted with caution due to high or unclear risk of bias of the included trials.

Effects of soya isoflavones and exercise on body composition and clinical risk factors of cardiovascular diseases in overweight postmenopausal women: a 6-month double-blind controlled trial

Results from a pilot project indicate that isoflavones and exercise could have an additive effect on body composition and clinical risk factors of CVD in postmenopausal women. The objective of the present study was to assess the combined effect of exercise and isoflavones in overweight-to-obese postmenopausal women. In this double-blind randomised controlled trial, 100 overweight-to-obese (BMI 29·9 (sd 3·2) kg/m2) postmenopausal women were assigned to four groups: (1) placebo (PLA); (2) isoflavones (ISO); (3) exercise and placebo (Ex+PLA); (4) exercise and isoflavones (Ex+ISO). The supplementation contained 70 mg/d of isoflavones. Exercise consisted of three weekly sessions of resistance training and aerobics. Outcome measures included fat mass (FM), lean body mass (LBM), bone mineral density, lipid profile, fasting glucose, fasting insulin and insulin resistance (homeostasis assessment model). The main effects of exercise were observed for total FM (P = 0·02), FM% (P < 0·01), trunk FM% (P = 0·05), arm FM% (P < 0·01), leg FM% (P = 0·02), arm LBM (P < 0·01), leg LBM (P = 0·02) and C-reactive protein (P < 0·01). A main effect was detected for isoflavones in improving leg FM% (P = 0·05). No interactions were observed between isoflavones and exercise. In conclusion, it was observed that 6 months of exercise brought favourable changes in total FM, FM% and LBM in overweight postmenopausal women. No synergistic effects were observed between exercise and isoflavones. However, isoflavones could have a beneficial effect on leg FM%.