Effects of isoflavonoids on blood pressure in subjects with high-normal ambulatory blood pressure levels: a randomized controlled trial

Genistein Alleviates Oxidative Stress and Inflammation in the Hypothalamic Paraventricular Nucleus by Activating the Sirt1/Nrf2 Pathway in High Salt-Induced Hypertension

Hypertension caused by a high-salt (HS) diet is one of the major causes of cardiovascular diseases. Underlining pathology includes oxidative stress and inflammation in the hypothalamic paraventricular nucleus (PVN). This study investigates genistein's (Gen) role in HS-induced hypertension and the underlying molecular mechanism. We placed male Wistar rats on HS (8% NaCl) or normal salt diet (0.3% NaCl). Then, we injected bilateral PVN in rats with Gen, vehicle, or nicotinamide (NAM) for 4 weeks. Tail cuff was used weekly to assess the systolic pressure, diastolic pressure, and mean arterial pressure (MAP). Cardiac hypertrophy was analyzed by heart weight/body weight ratio and wheat germ agglutinin staining. ELISA kits, Western blot, or dihydroethidium staining determined the levels of inflammatory cytokines and oxidative stress markers. Western blot measured protein levels of Sirt1, Ac-FOXO1, Nrf2, NQO-1, HO-1, and gp91^phox. Our result showed that PVN infusion of Gen significantly reduced the increase of systolic pressure, diastolic pressure, and MAP induced by an HS diet. Additionally, there was a decrease in cardiac hypertrophy and the levels of inflammatory cytokines in PVN and plasma. Meanwhile, PVN infusion of Gen notably inhibited the levels of oxidized glutathione and superoxide dismutase and improved the glutathione level and total antioxidant capacities and superoxide dismutase activities. It also decreased the level of reactive oxygen species and gp91^phox expression in PVN. Furthermore, Gen infusion markedly increases the Sirt1, Nrf2, HO-1, and NQO-1 levels and decreases the Ac-FOXO1 level. However, PVN infusion of NAM could significantly block these changes induced by Gen in HS diet rats. Our results demonstrated that PVN infusion of Gen could inhibit the progression of hypertension induced by an HS diet by activating the Sirt1/Nrf2 pathway.

Effects of flavonoid-rich fruits on hypertension in adults: a systematic review

OBJECTIVE

The objective of this systematic review was to synthesize the best available research evidence on the effectiveness of flavonoid-rich fruits in the treatment of hypertension.

INTRODUCTION

Hypertension is a serious public health concern as it contributes to a significant burden of disease, leading to millions of deaths globally. Complementary therapies including flavonoids have generated interest in assisting the treatment of hypertension. Flavonoids are a type of polyphenol abundant in fruits and a growing body of evidence suggests antihypertensive effects of the flavonoids due to their antioxidant properties. To date, no systematic review has been performed to collate the evidence on the effects of flavonoid-rich fruits on hypertension in adults.

INCLUSION CRITERIA

This systematic review included randomized controlled trials (RCTs) that compared the administration of any type of flavonoid-rich fruit or equivalent supplement with a placebo or other intervention in adults with hypertension. Trials that measured blood pressure using objective outcome measures such as a manual mercury sphygmomanometer were included. Studies that did not specify the flavonoid component of the fruit or fruit supplement were excluded from the review. Secondary outcomes, including change in weight, blood glucose level, triglycerides and total blood cholesterol levels, were also assessed.

METHODS

A three-step search was undertaken, including a comprehensive search of the MEDLINE, Embase, Cochrane Trials (CENTRAL) and CINAHL databases, in September 2018. We also searched Dissertation Abstracts International, ProQuest Dissertations and Theses, MedNar and ClinicalTrials.gov to identify unpublished studies. The title and abstracts of the studies were reviewed by two independent reviewers against the inclusion/exclusion criteria. The methodological quality of the potential studies for inclusion were assessed using the critical appraisal checklist for randomized controlled trials as recommended by JBI. Data were pooled in a statistical meta-analysis model. Subgroup-analysis according to type of intervention and length of intervention period was performed. Where statistical pooling was not possible, the findings have been presented in a narrative form.

RESULTS

Fifteen randomized controlled trials involving 572 participants were included in the review. The subclasses of flavonoids assessed included: anthocyanins, naringin, narirutin and flavan-3-ols. The overall methodological quality of the trials was high. Six trials investigated the effect of the flavonoid intervention on blood pressure within four weeks. Meta-analysis of four of the trials demonstrated no effect of flavonoids on systolic or diastolic blood pressure when compared to placebo (systolic mean difference = -1.02, 95% confidence interval [CI] -3.12, 1.07; p = 0.34, I = 0%; diastolic mean difference = -0.90, 95% CI -2.10, 0.31; p = 0.15, I = 0%). Similarly, pooled results from two crossover RCTs with two-timed dosed interventions in a 24-hour period demonstrated no effect on a reduction in diastolic blood pressure (p = 0.38) but did reveal evidence of a reduction in systolic blood pressure (p = 0). Six trials assessed blood pressure following the flavonoid intervention at more than four weeks follow-up. Meta-analysis of five of the trials demonstrated evidence of no effect on either systolic blood pressure (mean difference = -0.95, 95%CI -3.58, 1.68; p = 0.478, I = 0%) or diastolic blood pressure (mean difference = 0.86, 95%CI -1.11, 2.82; p = 0.393, I = 0%).

CONCLUSIONS

The findings of this systematic review should be interpreted with caution, given that the results are obtained from single-center trials with small sample sizes. Flavonoids have no effect on systolic and diastolic blood pressure. Further robust RCTs using sample sizes based on power calculations are needed to provide evidence for the use of flavonoid-rich fruits for the management of hypertension.

NutriGenomeDB: a nutrigenomics exploratory and analytical platform

Habitual consumption of certain foods has shown beneficial and protective effects against multiple chronic diseases. However, it is not clear by which molecular mechanisms they may exert their beneficial effects. Multiple -omic experiments available in public databases have generated gene expression data following the treatment of human cells with different food nutrients and bioactive compounds. Exploration of such data in an integrative manner offers excellent possibilities for gaining insights into the molecular effects of food compounds and bioactive molecules at the cellular level. Here we present NutriGenomeDB, a web-based application that hosts manually curated gene sets defined from gene expression signatures, after differential expression analysis of nutrigenomics experiments performed on human cells available in the Gene Expression Omnibus (GEO) repository. Through its web interface, users can explore gene expression data with interactive visualizations. In addition, external gene signatures can be connected with nutrigenomics gene sets using a gene pattern-matching algorithm. We further demonstrate how the application can capture the primary molecular mechanisms of a drug used to treat hypertension and thus connect its mode of action with hosted food compounds.

Relationship between legume consumption and metabolic syndrome: A systematic review and meta-analysis of observational studies

AIMS

The prevalence of metabolic syndrome (MetS) has been increasing in recent years. Investigation of whether consumption of legumes as a part of healthy diet could reduce the odds of MetS has led to inconsistent conclusions. Here, we performed the first meta-analysis of observational studies to analyze the association between legume consumption and prevalence of MetS.

DATA SYNTHESIS

PubMed, EMBASE, and Web of Science databases were searched to identify observational studies up to June 1, 2019. We extracted data from the studies included and performed quality assessments. Summary odds ratios (ORs) with 95% confidence intervals (CIs) were calculated using a random-effects model. Publication bias and subgroup and sensitivity analyses were also performed. We finally included four cross-sectional studies, two cohort studies, and one case-control study involving 56,028 participants. The summary OR revealed no statistically significant association between legume consumption and odds of MetS (OR = 0.93, 95% CI = 0.76-1.12, I² = 73.5%). Subgroup analysis of study characteristics and adjustment for confounding along with sensitivity analyses revealed no statistically significant differences. No evidence of publication bias was detected.

CONCLUSION

Legume consumption is not associated with the odds of MetS. These findings require validation in well-designed cohort studies and randomized clinical trials with accurate measurement of legume intake and strict control of confounders.

REGISTRATION

This study was registered with the International Prospective Register of Systematic Reviews (registration number: CRD42019131777).

Cardiovascular Effects of Flavonoids

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Cardiovascular Disease (CVD) is the major cause of death worldwide, especially in Western society. Flavonoids are a large group of polyphenolic compounds widely distributed in plants, present in a considerable amount in fruit and vegetable. Several epidemiological studies found an inverse association between flavonoids intake and mortality by CVD. The antioxidant effect of flavonoids was considered the main mechanism of action of flavonoids and other polyphenols. In recent years, the role of modulation of signaling pathways by direct interaction of flavonoids with multiple protein targets, namely kinases, has been increasingly recognized and involved in their cardiovascular protective effect. There are strong evidence, in in vitro and animal experimental models, that some flavonoids induce vasodilator effects, improve endothelial dysfunction and insulin resistance, exert platelet antiaggregant and atheroprotective effects, and reduce blood pressure. Despite interacting with multiple targets, flavonoids are surprisingly safe. This article reviews the recent evidence about cardiovascular effects that support a beneficial role of flavonoids on CVD and the potential molecular targets involved.

A review of the relative efficacy of dietary, nutritional supplements, lifestyle, and drug therapies in the management of hypertension

Despite advancements in hypertensive therapies, the prevalence of hypertension and associated morbidities are still immense. Physicians are in great need for updated information on novel and effective antihypertensive therapies. Therefore, the study objective was to provide comprehensive information on the efficacy of available antihypertensive therapies. Antihypertensive therapies were divided into four general approaches: diet, nutritional supplements, lifestyle modification, and conventional antihypertensive medications. A search of PubMed and Google Scholar resulted in an analysis of 30 antihypertensive therapies from meta-analyses and randomized-controlled trials (RCTs). The studies were analyzed using the American Heart Association/American College of Cardiology classification system. Calculated average blood pressure reductions were: (systolic/diastolic) 6/4 mmHg, 4/2 mmHg, 5/3 mmHg, and 9/5 mmHg for dietary, nutritional supplements, lifestyle, and medications, respectively. The results demonstrate that dietary, nutritional supplement and lifestyle strategies have a solid level of evidence to support their efficacy as antihypertensive strategies. These strategies can be as effective as medications and, in some cases, even more effective. Dissemination of this information to physicians/dietitians can help facilitate an important shift in hypertension management.

Genistein attenuates low temperature induced pulmonary hypertension in broiler chicks by modulating endothelial function

Pulmonary arterial hypertension is characterized by high pulmonary blood pressure, vascular remodeling and right ventricular hypertrophy. In the present study, we investigated whether genistein would prevent the development of low temperature-induced pulmonary hypertension in broilers. Hemodynamic parameters, vascular remodeling, the expression of endothelial nitric oxide and endothelin-1 content in lung tissue were evaluated. The results demonstrated that genistein significantly reduced pulmonary arterial hypertension and suppressed pulmonary arterial vascular remodeling without affecting broilers' performance. The beneficial effects appeared to be mediated by restoring endothelial function especially endothelial nitric oxide and endothelin-1, two critical vasoactive molecules that associated with the development of hypertension. Genistein supplementation might be a potential therapeutic strategy for the treatment of pulmonary hypertension.

A randomized controlled trial of the effects of flaxseed lignan complex on metabolic syndrome composite score and bone mineral in older adults

A randomized double-blind placebo controlled study design was used to assess the effects of flaxseed lignan complex supplementation during exercise training on a metabolic syndrome composite score and osteoporosis risk in older adults. A total of 100 subjects (>or=50 years) were randomized to receive flaxseed lignan (543 mg.day-1 in a 4050 mg complex) or placebo while completing a 6 month walking program (30-60 min.day-1, 5-6 days.week-1). Fasting serum glucose, triacylglycerol (TAG), high-density lipoprotein (HDL) cholesterol, low-density lipoprotein cholesterol, total cholesterol, interleukin-6, and tumor necrosis factor-alpha were measured every 2 months, while body composition, bone mineral density, and resting blood pressure were assessed at baseline and at 6 months. A composite Z score of 6 risk factors for metabolic syndrome (fasting glucose, HDL cholesterol, TAG, abdominal adiposity, blood pressure, and inflammatory cytokines) was calculated at baseline and at 6 months. Men taking placebo increased metabolic syndrome composite Z score (p < 0.05), but there were no changes in the other groups. A significant group x sex x time interaction was noted for TAG (p = 0.017) and diastolic blood pressure (p = 0.046), with men taking flaxseed lignan decreasing diastolic blood pressure relative to men taking placebo, and men taking placebo increasing TAG relative to men taking flax lignan. There were no differences between groups for change in bone measures, body composition, lipoproteins, or cytokines. Males taking the flaxseed lignan complex reduced metabolic syndrome score relative to men taking placebo, but a similar trend was not seen in females. Flaxseed lignan had no effect on bone mineral density or content, body composition, lipoproteins, glucose, or inflammation.

Isoflavone content and its potential contribution to the antihypertensive activity in soybean Angiotensin I converting enzyme inhibitory peptides

A soybean angiotensin I converting enzyme (ACE) inhibitory peptide fraction was reported to have antihypertensive activity in a rat study. The purpose of the present study was to examine if the presence of isoflavones in the soybean ACE inhibitory peptide fraction may contribute to the blood-pressure-lowering property. The isoflavone concentration in soybean samples was analyzed on a C 18 reverse-phase column using a two-step gradient solvent system. Producing soybean hydrolysate led to a nearly 40% loss of isoflavones compared with the original soybean flour, but the isoflavone composition did not change and the dominant isoflavone chemicals remained as 6''-O-malonylgenistin and 6''-O-malonyldaidzin. Ion exchange chromatography affected significantly both the content and the composition of the isoflavones. The dominant isoflavones in the ion-exchanged fraction were aglycones and nonacylated isoflavones, accounting for 95.8% of the total amount of 987.7 microg/g. It was calculated that the isoflavone content in the soybean ACE inhibitory peptide fraction was 25 times less than the minimal effective isoflavone dose reported. In vitro study also showed that adding isoflavones into both soybean flour hydrolysate and soybean ACE inhibitory peptide samples to a concentration of as high as 31.5% (w/w) did not affect ACE inhibitory activity (IC 50 values). The findings along with previously published results indicated that the contribution of isoflavones in soybean ACE inhibitory peptide fraction to the blood-pressure-lowering property in a short-term feeding study might be negligible.

Modulation of the genomic estrogen receptor pathway by water extracts of Cirsium japonicum

We investigated the estrogenic activity of Cirsium japonicum water extracts, which have long been used to treat vascular-related diseases. The activity of the extracts was characterized in a transient transfection system, using estrogen receptor isoforms and estrogen-responsive luciferase plasmids in HEK 293 cells. The extract activated both and estrogen receptors. Activation was inhibited by the estrogen receptor antagonist ICI 182,780, indicating that the effects were mediated through the estrogen receptor isoforms. Treatment with the extracts increased expression of the progesterone receptor and pS2 genes and expression of estrogen receptor was decreased in MCF-7 cells. These results suggested that the Cirsium japonicum water extracts showed estrogenic effects and may be a potential clinical application for treatment of estrogen related vascular diseases.

[Usefulness of phyto-oestrogens in reduction of blood pressure. Systematic review and meta-analysis]

OBJECTIVES

To determine whether treatment with phyto-oestrogens or soya protein succeeds in lowering blood pressure.

DESIGN

A systematic review, evaluating all the observation studies and clinical trials, was conducted, followed by a meta-analysis to evaluate blood pressure variations in patients treated with phyto-oestrogens. SEARCH: The search strategy adopted used the terms "phyto-oestrogens," "soya meals," "hypertension," and "blood pressure."

DATA SOURCES

The data bases MEDLINE, EMBASE, Cochrane, OVID were used, without time or language restrictions. References in the relevant articles were searched for manually.

STUDY SELECTION

Two independent reviewers analysed the studies found in the search.

DATA EXTRACTION

The Jadad scale was used for the clinical trials and the numerical data in the text or referred to in tables were extracted. Evaluation was made of which observational and experimental articles showed a drop in blood pressure with phyto-oestrogens and which did not. In the meta-analysis, data on sample size, difference in blood pressure before and after intervention and standard deviation were extracted from each study. The weighted difference of means was used with the model of randomised effects. The Review Manager v4.2.9 programme was used.

RESULTS

No significant variations in blood pressure were found, whether systolic (-1.20 mm Hg; 95% CI, -2.80 to 0.41 mm Hg) or diastolic (-1.31 mm Hg; 95% CI, -2.73 to 0.11). If there were any variations, they are clinically of little importance. There was also an important degree of both statistical and clinical heterogeneity.

CONCLUSIONS

There are no statistically significant or clinically important differences in blood pressure between patients treated with phyto-oestrogens and those not treated.

Protein intake and blood pressure in cardiovascular disease

Raised blood pressure (BP) is a major cause of CHD and the leading cause of stroke. Although BP rises with age in most populations, there are remote populations around the world where BP does not rise with age and where the high prevalence of high BP and frank hypertension seen in the UK and other Western countries in the older age-groups is not found. However, when such populations migrate to urban settings, their BPs rise, indicating that the population-wide BP problem is largely environmental in origin. Thus, a substantial body of evidence has accumulated on the importance of dietary factors in BP (Na and alcohol intakes (direct relationship) and K intake (inverse relationship)) as well as body weight (direct relationship). More recently, attention has shifted to other dietary factors that might affect BP. Data from studies of vegetarians (who tend to have lower BP than meat-eating populations) as well as clinical data on the adverse effects of protein intake in patients with renal insufficiency led to the view in Western countries that dietary (animal or total) protein had an adverse effect on BP. By contrast, studies in Japan and China suggested that dietary protein might be protective of high BP and stroke. Recent epidemiological studies have found inverse associations between dietary protein intake and BP, consistent with this view, and supported by some evidence from animal studies. Recent controlled clinical trials of soyabean supplementation have also suggested a BP-lowering effect of protein intake. Results of further large-scale epidemiological studies of protein and BP are awaited.

Soy inclusion in the diet improves features of the metabolic syndrome: a randomized crossover study in postmenopausal women

BACKGROUND

Little evidence exists regarding the effects of soy consumption on the metabolic syndrome in humans.

OBJECTIVE

We aimed to determine the effects of soy consumption on components of the metabolic syndrome, plasma lipids, lipoproteins, insulin resistance, and glycemic control in postmenopausal women with the metabolic syndrome.

DESIGN

This randomized crossover clinical trial was undertaken in 42 postmenopausal women with the metabolic syndrome. Participants were randomly assigned to consume a control diet (Dietary Approaches to Stop Hypertension, DASH), a soy-protein diet, or a soy-nut diet, each for 8 wk. Red meat in the DASH period was replaced by soy-protein in the soy-protein period and by soy-nut in the soy-nut period.

RESULTS

The soy-nut regimen decreased the homeostasis model of assessment-insulin resistance score significantly compared with the soy-protein (difference in percentage change: -7.4 +/- 0.8; P < 0.01) or control (-12.9 +/- 0.9; P < 0.01) diets. Consumption of soy-nut also reduced fasting plasma glucose more significantly than did the soy-protein (-5.3 +/- 0.5%; P < 0.01) or control (-5.1 +/- 0.6%; P < 0.01) diet. The soy-nut regimen decreased LDL cholesterol more than did the soy-protein period (-5.0 +/- 0.6%; P < 0.01) and the control (-9.5 +/- 0.6%; P < 0.01) diet. Soy-nut consumption significantly reduced serum C-peptide concentrations compared with control diet (-8.0 +/- 2.1; P < 0.01), but consumption of soy-protein did not.

CONCLUSION

Short-term soy-nut consumption improved glycemic control and lipid profiles in postmenopausal women with the metabolic syndrome.

Isoflavonas en mujeres menopáusicas

Phytoestrogens are composed derivatives of vegetables. The 2 main classes of interest to human health are lignans and isoflavones. Isoflavones exist in at least 15 different chemical forms and their effect on human health has been investigated to some extent (particularly, genistein and daidzein as high levels of these compounds are present in soybean). Isoflavones have similar structure to oestrogen and have the capacity to exert both oestrogenic and anti oestrogenic effects. They may block the effects of oestrogen in some tissues (e. g., the breast and endometrium), but act like an oestrogen in providing possible protection against bone loss and heart disease. Lignans are much more widespread in plant foods but investigation has been limited due to the complexity of measurement. The increasing interest in the use of the soybean and the phytoestrogens derived from the soybean is due to the results published on experimental animal actions, and in human case-control studies. There are many observational and epidemiologists studies that suggest the potential benefit of isoflavones on the menopause symptoms, the cardiovascular system, the osteoporosis and the estrogen dependent cancers, but many open questions exist. We must be very strict with certain observational studies by the possible influences of collateral factors to the isoflavones (exercise, type of diet, etc.), and attribute the beneficial effects may be due to own treatment.

Comparative effects of enzogenol and vitamin C supplementation versus vitamin C alone on endothelial function and biochemical markers of oxidative stress and inflammation in chronic smokers

Chronic smoking is associated with endothelial dysfunction and inflammation, with oxidative stress contributing to both these processes. In this study, we investigated the effect of combined antioxidant treatment with Enzogenol, a flavonoid extract from the bark of Pinus radiata and vitamin C, over and above vitamin C alone, on endothelial function, plasma markers of inflammation and oxidative stress, blood pressure (BP) and anthropometrics. Forty-four chronic smokers without established cardiovascular disease were assigned randomly to receive either 480 mg Enzogenol and 60 mg vitamin C, or 60 mg vitamin C alone daily for 12 weeks. Endothelial function in the brachial artery was assessed by flow-mediated vasodilation (FMD). FMD improved in both treatment groups (p < 0.001), with no significant difference between the two groups (p = 0.84). In the group receiving Enzogenol and vitamin C, protein carbonyl levels were significantly reduced compared to the group taking vitamin C alone (p = 0.03). Enzogenol and vitamin C resulted in a significant reduction in fibrinogen levels in heavy smokers compared with vitamin C alone (p < 0.009). These findings demonstrated that co-supplementation with Enzogenol and vitamin C in smokers conferred no additional beneficial effect on macrovascular endothelial function over and above that seen in the vitamin C alone group. However, Enzogenol did demonstrate additional favourable effects on protein oxidative damage and fibrinogen levels.

Critical review of health effects of soyabean phyto-oestrogens in post-menopausal women

A consensus view of soyabean phyto-oestrogens in clinical interventions in post-menopausal women is presented that is based on data from the EU-funded project Phytohealth. The phyto-oestrogens, primarily genistein and daidzein, were given as soyabean-protein isolates, whole-soyabean foods or extracts, supplements or pure compounds. A comprehensive literature search was conducted with well-defined inclusion or exclusion criteria. For areas for which substantial research exists only placebo-controlled double-blind randomised controlled trials (RCT) conducted on healthy post-menopausal women were included. For emerging areas all available human studies in post-menopausal women were reviewed. In order to make cross comparisons between studies the doses of isoflavones were calculated as aglycone equivalents. There is a suggestion, but no conclusive evidence, that isoflavones from the sources studied so far have a beneficial effect on bone health. The consumption of whole-soyabean foods and soyabean-protein isolates has some beneficial effects on lipid markers of cardiovascular risk. The consumption of isolated isoflavones does not affect blood lipid levels or blood pressure, although it may improve endothelial function. For menopausal symptoms there is currently limited evidence that soyabean-protein isolates, soyabean foods or red-clover (Trifolium pratense L.) extract are effective but soyabean isoflavone extracts may be effective in reducing hot flushes. There are too few RCT studies to reach conclusions on the effects of isoflavones on breast cancer, colon cancer, diabetes or cognitive function. The health benefits of soyabean phyto-oestrogens in healthy post-menopausal women are subtle and even some well-designed studies do not show protective effects. Future studies should focus on high-risk post-menopausal women, especially in the areas of diabetes, CVD, breast cancer and bone health.

Dietary soy isoflavone induced increases in antioxidant and eNOS gene expression lead to improved endothelial function and reduced blood pressure in vivo

Epidemiological evidence suggests that populations consuming large amounts of soy protein have a reduced incidence of coronary heart disease (1-5). The cardiovascular risks associated with conventional hormone replacement therapy in postmenopausal women (5-7) have precipitated a search for alternative estrogen receptor modulators. Here we report that long-term feeding of rats with a soy protein-rich (SP) diet during gestation and adult life results in decreased oxidative stress, improved endothelial function, and reduced blood pressure in vivo measured by radiotelemetry in aged male offspring. Improved vascular reactivity in animals fed an SP diet was paralleled by increased mitochondrial glutathione and mRNA levels for endothelial nitric oxide synthase (eNOS) and the antioxidant enzymes manganese superoxide dismutase and cytochrome c oxidase. Reduced eNOS and antioxidant gene expression, impaired endothelial function, and elevated blood pressure in animals fed a soy-deficient diet was reversed after refeeding them an SP diet for 6 months. Our findings suggest that an SP diet increases eNOS and antioxidant gene expression in the vasculature and other tissues, resulting in reduced oxidative stress and increased NO bioavailability. The improvement in endothelial function, increased gene expression, and reduced blood pressure by soy isoflavones have implications for alternative therapy for postmenopausal women and patients at risk of coronary heart disease.

The combination of vitamin C and grape-seed polyphenols increases blood pressure: a randomized, double-blind, placebo-controlled trial

BACKGROUND

There is growing evidence that oxidative stress contributes to the pathogenesis of hypertension and endothelial dysfunction. Thus, dietary antioxidants may beneficially influence blood pressure (BP) and endothelial function by reducing oxidative stress.

OBJECTIVE

To determine if vitamin C and polyphenols, alone or in combination, can lower BP, improve endothelial function and reduce oxidative stress in hypertensive individuals.

DESIGN

A total of 69 treated hypertensive individuals with a mean 24-h ambulatory systolic blood pressure > or = 125 mmHg participated in a randomized, double-blind, placebo-controlled, factorial trial. Following a 3-week washout, participants received 500 mg/day vitamin C, 1000 mg/day grape-seed polyphenols, both vitamin C and polyphenols, or neither for 6 weeks. At baseline and post-intervention, 24-h ambulatory BP, ultrasound-assessed endothelium-dependent and -independent vasodilation of the brachial artery, and markers of oxidative damage, (plasma and urinary F2-isoprostanes, oxidized low-density lipoproteins and plasma tocopherols), were measured.

RESULTS

A significant interaction between grape-seed and vitamin C treatments for effects on BP was observed. Vitamin C alone reduced systolic BP versus placebo (-1.8 +/- 0.8 mmHg, P = 0.03), while polyphenols did not (-1.3 +/- 0.8 mmHg, P = 0.12). However, treatment with the combination of vitamin C and polyphenols increased systolic BP (4.8 +/- 0.9 mmHg versus placebo; 6.6 +/- 0.8 mmHg versus vitamin C; 6.1 +/- 0.9 mmHg versus polyphenols mmHg, each P < 0.0001) and diastolic BP (2.7 +/- 0.6 mmHg, P < 0.0001 versus placebo; 1.5 +/- 0.6 mmHg, P = 0.016 versus vitamin C; 3.2 +/- 0.7 mmHg, P < 0.0001 versus polyphenols). Endothelium-dependent and -independent vasodilation, and markers of oxidative damage were not significantly altered.

CONCLUSION

Although the mechanism remains to be elucidated, these results suggest caution for hypertensive subjects taking supplements containing combinations of vitamin C and polyphenols.

Isoflavones and postmenopausal women: a critical review

Isoflavonic phytoestrogens, or isoflavones, constitute a class of phytoestrogens that have properties similar to selective estrogen receptor modulators, and have attracted a substantial degree of attention in recent years, particularly as a possible alternative to the conventional hormone replacement therapy regimens used by postmenopausal women. Despite great promise, it is difficult to make many specific recommendations about their use at the current time, in light of the many outstanding questions that hopefully will be answered in the future by focused interventional studies involving humans. Studies to date indicate that the use of isoflavones to address vasomotor symptoms provides at most small benefits beyond a placebo effect, and no benefit for genital atrophy. As for postmenopausal women whose primary concern is cardiovascular disease, the recommendation of the American Heart Association to include soy protein foods as part of an otherwise healthy diet is well justified, and similarly the substitution of supplements containing soy protein for animal protein can also be recommended. The use of purified isoflavone supplements not containing soy protein may have some cardiovascular benefits, but these appear to be less substantial in degree than those provided by soy protein with isoflavones. In particular, more research is needed to assess the effects of isoflavones on osteoporosis, for which no recommendation regarding isoflavones can be made based on the current data. Also, isoflavones should not be taken by postmenopausal women for the specific purpose of decreasing their risk of breast or endometrial cancer, although, at least for those without pre-existing disease or at high risk, it seems quite unlikely that isoflavone use is harmful in this regard.

Effects of soy isoflavones on endothelial function in healthy postmenopausal women

OBJECTIVE

To evaluate the effects of soy isoflavone administration on endothelial function in healthy postmenopausal women.

DESIGN

Sixty naturally postmenopausal women were randomly assigned to receive isoflavone or placebo tablets for 6 months. Endothelium-dependent vasodilatation was measured by brachial reactivity technique along with levels of plasma soluble intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), E-selectin, P-selectin and soluble thrombomodulin, von Willebrand factor, and tissue plasminogen activator. Differences between endothelium-dependent and endothelium-independent vasodilatation were assessed by evaluating brachial reactivity parameters after reactive hyperemia and after sublingual administration of nitroglycerin; furthermore, in the active group, the effect of isoflavones was also evaluated during the intra-arterial infusion of N-monomethyl-L-arginine. Serum levels of lipids [high-density lipoprotein and low-density lipoprotein cholesterol, triglycerides and lipoprotein(a)] and hemostatic factors (prothrombin, fibrinogen, plasminogen activator inhibitor-1, and fibrin D-dimer) were also measured. To confirm the absorption of isoflavones, their blood concentrations were determined.

RESULTS

Isoflavone treatment versus placebo was associated with a significant improvement in endothelium-dependent vasodilatation but had no impact on endothelial-independent arterial diameter and flow. Intra-arterial infusion of N-monomethyl-L-arginine inhibited the significant effect of isoflavones on endothelium-mediated vasodilatation. Furthermore, isoflavone group experienced statistically significant reductions in plasma concentrations of ICAM-1, VCAM-1, and E-selectin. Levels of soluble thrombomodulin, von Willebrand factor, tissue plasminogen activator, lipids, and hemostatic factors did not change significantly throughout the study in both groups.

CONCLUSIONS

Our findings suggest a positive influence of soy isoflavones on endothelial function in healthy postmenopausal women as evidenced by an improvement in endothelium-dependent vasodilatation and a reduction in plasma adhesion molecule levels.

Comparison between daidzein and genistein antioxidant activity in primary and cancer lymphocytes

The main objective of this study was to compare the protective effect of daidzein and genistein against induced oxidative damage in Jurkat T-cell line and in peripheral blood lymphocytes of healthy subjects. After supplementation of cells with isoflavones (from 2.5 to 20micromol/L in Jurkat T-cell and from 0.01 to 2.5micromol/L in primary lymphocytes, 24h), we determined DNA damage induced by hydrogen peroxide using the comet assay and lipid peroxidation evaluating malondialdehyde (MDA) production after ferrous ion treatment. Supplementation of Jurkat cells and primary lymphocytes with both isoflavones significantly increased DNA protection from oxidative damage at concentrations between 0.1 and 5micromol/L (P<0.05), and with just daidzein, at concentrations higher than 2.5micromol/L, there was a decrease in the production of MDA (P<0.05). Our results seem to support that daidzein is just as effective as genistein in protecting cells against oxidative damage especially with respect to DNA. Moreover, since the protective effect was found at concentrations reachable in plasma after soy consumption (less than 2micromol/L), it can be assumed that the antioxidant activity of isoflavones could really contribute to the healthy properties of soy.

Randomized controlled trial of the effects of soy protein containing isoflavones on vascular function in postmenopausal women

BACKGROUND

The incidence of cardiovascular disease increases after menopause, possibly because of the decline in estrogen. Soy protein, a rich source of estrogen-like isoflavones, is hypothesized to improve vascular function.

OBJECTIVE

The objective of this study was to investigate whether supplementation with soy protein, a rich source of estrogen-like isoflavones, improves vascular function.

DESIGN

We performed a 12-mo double-blind randomized trial to compare the effects of soy protein containing 99 mg isoflavones/d (aglycone weights) with those of milk protein (placebo) on blood pressure and endothelial function in 202 postmenopausal women aged 60-75 y.

RESULTS

Changes in endothelial function during the intervention were not significantly different between the soy and the placebo groups. After the intervention, systolic blood pressure increased in the soy group significantly more than it did in the placebo group; the difference in change was 4.3 mm Hg (95% CI: 0.3, 8.4 mm Hg; P = 0.04) for systolic blood pressure, but only 2.0 mm Hg (95% CI: -0.74, 4.71 mm Hg; P = 0.15) for diastolic blood pressure. In the soy group only, systolic and diastolic blood pressure decreased and endothelial function improved in the equol producers, whereas systolic and diastolic blood pressure increased and endothelial function deteriorated in the equol nonproducers.

CONCLUSIONS

The results of this trial do not support the hypothesis that soy protein containing isoflavones have beneficial effects on vascular function in older postmenopausal women. Whether certain subgroups of women (eg, equol producers) do benefit from the intervention remains to be elucidated.

Soy, isoflavones and atherosclerosis

Consumption of soy protein is associated with a lower risk of cardiovascular disease in man, and reduced atherosclerosis in a variety of experimental animals. Although a portion of the cardiovascular protective effects appears to be due to reductions in plasma lipoprotein concentration, in most people the magnitude of this effect is relatively small. In many, but not all studies using animal models, the reduction in atherosclerosis is in part independent of changes in plasma lipids and lipoproteins. This implies that there may be a direct effect on the arterial wall of one or more of the components in soyprotein that reduces susceptibility to atherosclerosis. The most actively studied components of soy protein that may be responsible for these anti-atherogenic effects are the isoflavones and various protein factions. Extraction of isoflavones and other alcohol-soluble components from soy protein lowers, but does not eliminate its ability to reduce atherosclerosis. Surprisingly, in most studies, adding back the isoflavone-rich alcohol extract to the previously extracted soy protein, or to another protein, does not restore its lipoprotein lowering or anti-atherogenic properties. This implies that alcohol extraction either destroys an active component of soy, alters the structural integrity of the soy proteins, or disassociates a required isoflavone-soy protein complex. Understanding the mechanism of this effect is an important goal for future research. Likewise, the sites of action on the arterial wall, and the mechanisms by which various soy components act to reduce atherosclerosis are just now being studied. The recent demonstration that expression of estrogen receptor alpha is required for atheroprotection by soy protein provides important new mechanistic insight. Other properties of soy, including antioxidant, anti-inflammatory and potentially antithrombogenic properties need to be explored more mechanistically before the full potential of dietary soy protein for the protection from cardiovascular disease will be known.

Limited lipid-lowering effects of regular consumption of whole soybean foods

AIM

To examine cardiovascular health benefits of foods containing a whole soybean extract.

METHODS

The study design was a randomized, placebo-controlled crossover trial of consuming soy-based milk and yoghurt (treatment) or equivalent dairy products (control) for 5 weeks each. Twenty-six mildly hypercholesterolaemic and/or hypertensive volunteers were recruited from the community as study volunteers, of which 23 completed. Main outcome measures included clinic and ambulatory blood pressure, arterial compliance, lipids, fatty acids and isoflavones in fasted blood and 24-hour urinary isoflavone excretion. Nutrient intakes were assessed initially and after each 5-week period. Multiple regression analyses were used to determine predictor variables in statistical models; order effects were tested by repeated measures ANOVA. Changes in Lp(a) were determined by Wilcoxon signed ranks tests; other differences between treatment and control were assessed by t tests.

RESULTS

Plasma and urinary isoflavones were markedly increased by whole soy supplementation but there were no overall differences in plasma lipids, blood pressure or arterial compliance between the soy and dairy diets. However, in 8 equol-positive subjects (equol detected in either plasma or urine), retrospective analysis revealed significant reductions in total cholesterol (8.5%), LDL cholesterol (10%), LDL:HDL ratio (13.5%), plasma triglycerides (21%) and lipoprotein(a) (11%) with the soy diet. These reductions were independent of changes in polyunsaturated fat and other macronutrient intakes.

CONCLUSIONS

Regular consumption of whole soybean milk and yogurt products had no effect on plasma lipids, blood pressure or arterial compliance in at-risk subjects, despite substantially increasing isoflavone levels in blood and urine. Retrospective analysis suggests that improvement of plasma lipids may have been limited to equol-positive subjects.

Effects of dietary supplementation with isoflavones from red clover on ambulatory blood pressure and endothelial function in postmenopausal type 2 diabetes

OBJECTIVE

The aim of this study was to determine whether dietary supplementation with isoflavones from red clover affected ambulatory blood pressure and forearm vascular endothelial function in postmenopausal type 2 diabetic women.

DESIGN

Sixteen postmenopausal type 2 diabetics treated with diet or oral hypoglycaemic therapy completed a randomized double-blind crossover trial of dietary supplementation with isoflavones from red clover (approximately 50 mg/day) for 4 weeks compared to placebo. Twenty-four-hour ambulatory blood pressure recordings and forearm vascular responses to acetylcholine, nitroprusside and L-nitromonomethylarginine (L-NMMA) were measured at the end of each treatment period.

RESULTS

Mean daytime systolic and diastolic blood pressures were significantly lower during isoflavone therapy compared to placebo (-8.0 +/- 3.4 and -4.3 +/- 1.9 mmHg respectively, p < 0.05). The increase in forearm vascular resistance following L-NMMA was significantly greater during isoflavone supplementation (20.9 +/- 6.5) than placebo (3.7 +/- 2.9 arbitrary units, p < 0.05), suggesting an improvement in basal endothelial function. Plasma lipoproteins, glycated haemoglobin and forearm vascular responses to acetylcholine and nitroprusside did not differ significantly between isoflavone and placebo therapy.

CONCLUSION

Isoflavone supplementation from red clover may favourably influence blood pressure and endothelial function in postmenopausal type 2 diabetic women.

Association of blood pressure with intake of soy products and other food groups in Japanese men and women

BACKGROUND

Soy diet has been suggested to have antihypertensive effect in animal studies. The present study examined the cross-sectional relationship between blood pressure and intake of soy products and other food groups in Japanese men and women.

METHODS

Blood pressure was measured in Japanese 294 men and 330 women (246 premenopausal and 84 peri- and postmenopausal women) who participated in a health check-up program provided by a general hospital. Intake of various food groups and nutrients was estimated from a validated semiquantitative food frequency questionnaire.

RESULTS

In men, soy product intake was inversely significantly correlated with diastolic blood pressure (r = -0.12, P = 0.04) after controlling for age, total energy, smoking status, body mass index, and intake of alcohol, salt and seaweeds. The correlation of soy product intake with systolic blood pressure was of borderline significance (r = -0.10, P = 0.09). Systolic blood pressure was inversely correlated with intake of vegetables (r = -0.12, P = 0.04) and dairy products (r = -0.12, P = 0.05). There were no significant correlations between soy product intake and diastolic blood pressure in women.

CONCLUSIONS

These results indicate a mild effect of soy intake on blood pressure reduction in men.

Isoflavones: their effects on cardiovascular risk and functions

PURPOSE OF REVIEW

Isoflavones - plant polyphenols with oestrogenic activity - are becoming widely distributed in foods and sold as nutriceuticals. Their similarity to steroidal oestrogens has stimulated research into potential cardiovascular benefits. The two major areas, those of lipid lowering and of improved vascular function, are reviewed.

RECENT FINDINGS

A major plasma cholesterol lowering effect has not been sustained in recent publications. Relatively minor reductions in LDL-cholesterol or non-HDL-cholesterol have generally been reported, but studies in which no reduction was found have also been reported. Fewer publications have dealt with effects on vasculature, but these have been more consistent. Arterial compliance, a parameter of the elasticity or distensibility of large arteries, is improved by as much as has been reported for estrogens. Vasodilatory effects on the microcirculation with isoflavones or their metabolites may provide opportunities for pharmacological intervention. The metabolism of isoflavones is reviewed briefly in order to highlight its complexity.

SUMMARY

Although research has failed to demonstrate substantial cholesterol lowering with dietary isoflavones, consumption of legumes is generally to be encouraged as part of the overall strategy for lowering plasma lipids. The favourable effects of ingested or infused isoflavones on several parameters of arterial function suggest an alternative explanation for the apparent low prevalence of coronary disease in populations that eat legumes as a staple food. A better understanding of the pharmacokinetics and bioavailabilty of individual isoflavones is needed if definitive studies are to be designed.

Relationship of urinary sodium/potassium excretion and calcium intake to blood pressure and prevalence of hypertension among older Chinese vegetarians

OBJECTIVE

To examine the associations of dietary sodium and potassium, as reflected by the urinary sodium/potassium excretion, and calcium intake with blood pressure and the prevalence of hypertension among older Chinese vegetarians in Hong Kong.

DESIGN

Cross-sectional study.

SETTING

Research clinic in a teaching hospital in Hong Kong.

SUBJECTS

A total of 111 ambulatory vegetarians over the age of 55 were recruited from members of religious organizations or old age hostels.

MAIN OUTCOME MEASURES

Hypertension was defined as supine blood pressure >140/90 mmHg or a history of hypertension. Dietary sodium, potassium and calcium intakes were assessed by 24 h recall method or fasting urinary sodium or potassium/creatinine ratios.

RESULTS

Seventy-one subjects (64%) were found to have hypertension. Compared with normotensive subjects, hypertensive subjects had lower calcium intake (411+/-s.d. 324 vs 589+/-428 mg, P=0.04), but higher urinary sodium/creatinine ratio (32.6+/-19.3 vs 21.0+/-12.4, P=0.00) and sodium/potassium ratio (4.7+/-2.8 vs 3.4+/-2.3, P=0.02). Among 88 subjects not taking diuretics or antihypertensive drugs, systolic blood pressure was related to calcium intake (r=-0.40), urinary sodium/creatinine ratio (r=0.39), urinary sodium/potassium ratio (r=0.30) and age (r=0.23). Diastolic blood pressure was related to urinary sodium/creatinine (r=0.29). Twenty-three subjects with high urinary sodium/potassium and low calcium intake and 16 subjects with low urinary sodium/potassium ratio and high calcium intake differed markedly with respect to systolic blood pressure (159+/-26 vs 130+/-15 mmHg) and prevalence of hypertension (78% vs 25%).

CONCLUSIONS

Older Chinese vegetarians are predisposed to hypertension because of their sodium-rich but calcium-deficient diets.

Dietary compounds in relation to dietary diversity and human health

The human diet contains numerous endocrine-active compounds that influence mammalian physiology. The effects of these dietary compounds may be mediated by interaction with well-characterized intracellular hormone receptors or by other effects on patterns of endogenous hormone production, metabolism, target tissue signaling, growth, or differentiation. Because humans evolved as omnivores, the spectrum of dietary compounds that can be tolerated at modest levels of intake without frank toxicity is broad. Modest intake of these diverse nonnutritive endocrine-active compounds offers potential human health benefits through modulation of metabolic and hormonal responses, especially in sedentary individuals consuming a highly refined diet.

Fitoestrogênios: posicionamento do Departamento de Endocrinologia Feminina da Sociedade Brasileira de Endocrinologia e Metabologia (SBEM)

Para avaliar a utilidade dos fitoestrogênios (FE) na terapia de reposição hormonal da menopausa (TRHM), o Departamento de Endocrinologia Feminina da SBEM reuniu um grupo de especialistas para fazer uma revisão bibliográfica e selecionar trabalhos nos quais a metodologia adotada demonstrasse rigor científico. Os FE têm ações estrogênicas e antiestrogênicas, predominantemente sobre os receptores de estrogênios (E) beta, com potência estrogênica muito inferior à do estradiol. O conteúdo de FE nas suas fontes vegetais é variável, dependendo da forma de cultivo, safra, armazenamento e industrialização. Também a conversão dos precursores em fitormônios ativos no organismo humano tem grande variabilidade individual. A maior parte das pesquisas com FE é realizada in vitro ou com animais de laboratório, nem sempre podendo ser extrapoladas para humanos. Com relação à síndrome do climatério, alguns estudos sugerem discreta melhora dos fogachos, sem modificação do ressecamento vaginal ou das alterações do humor. No metabolismo lipídico, alimentação rica em soja, mas não isoflavonas isoladamente, promove redução do colesterol total, do LDL-col e dos triglicerídeos, mas não elevam o HDL-col, como os E, e podem causar aumento da lipoproteína (a), que os E contribuem para diminuir. Embora alguns estudos de curta duração sugiram aumento da densidade mineral óssea com uso de isoflavonas, não há demonstração de redução de fraturas. Conclui-se que não há evidências convincentes que justifiquem o uso de FE ou alimentação rica em soja como alternativa para a TRHM.

Dietary soy and soy isoflavones have gender-specific effects on plasma lipids and isoflavones in golden Syrian f(1)b hybrid hamsters

The specific components of soy responsible for its beneficial effects on plasma lipids are unknown. Golden Syrian F(1)B Hybrid hamsters (75 male, 74 female) were evaluated for the effect of dietary soy and soy isoflavones on plasma lipids. They were fed the following diets for 16 wk: casein/lactalbumin (C/L), soy protein with isoflavones [Soy(+)], soy protein with isoflavones removed [Soy(-)], Soy(-) plus isoflavone extract (IF), and C/L + IF. At necropsy, plasma total cholesterol, HDL cholesterol (HDLC), LDL + VLDL cholesterol (LDL + VLDLC), isoflavones, and uterine and accessory gland weights were measured. Male hamsters fed the three soy-containing diets had lower LDL + VLDLC concentrations than those fed the two C/L diets (P < 0.01), and those fed Soy(-) + IF did not differ from those fed Soy(+). In females, diet did not affect plasma LDL + VLDLC concentration. Females fed Soy(+) or Soy(-) had higher HDLC (P < 0.05) than those fed C/L. HDLC was not affected by diet in males. Due to higher equol production (P < 0.01), males had greater plasma isoflavone concentrations (P < 0.01) than females. There was a positive association between plasma total isoflavones and LDL + VLDLC (r = 0.65, P < 0.05) in females. These data suggest gender differences in plasma lipid and isoflavone responses to soy- based diets in Syrian F(1)B Hybrid hamsters, which offer an opportunity to explore effects of sex hormones on isoflavone metabolism and the effects of isoflavones on lipid metabolism.

Pressor responsiveness to angiotensin in soy-fed spontaneously hypertensive rats

Dietary soy may attenuate the development of arterial hypertension. In addition, some soy-containing foods exhibit angiotensin-converting enzyme (ACE) inhibitory properties. Accordingly, we tested the hypothesis that ACE inhibition contributes to the antihypertensive effect of dietary soy. Mean arterial blood pressure (MAP) was recorded from conscious spontaneously hypertensive rats (SHR) at least 24 h after the implantation of catheters. Cumulative dose-response curves to intravenous angiotensin I (AI) (5-100 ng x kg(-1) x min(-1)) and angiotensin II (AII) (1-20 ng x kg(-1) x min(-1)) were constructed for male, sham-operated female, and ovariectomized female (OVX) SHR that were maintained on either casein or soy diets. The soy diet was associated with a significant reduction in baseline MAP in the OVX SHR (approximately 20 mmHg, 1 mmHg = 133.322 Pa). AI and AII infusions caused graded increases in MAP in all groups. However, there was no significant attenuation of the pressor responses to AI in the soy-fed SHR. Conversely, we observed a significant rightward displacement of the AII dose-response curves in the soy-fed sham-operated and OVX SHR. We conclude that ACE inhibition does not account for the antihypertensive effect of dietary soy in mature SHR.

Safety and pharmacokinetics of purified soy isoflavones: single-dose administration to postmenopausal women

BACKGROUND

Soy isoflavones are being evaluated as chemopreventive agents for breast and other cancers.

OBJECTIVE

The objective was to perform safety and pharmacokinetic studies of purified unconjugated isoflavone preparations containing genistein, daidzein, and glycitein in postmenopausal women.

DESIGN

Twenty-four healthy postmenopausal women ingested a single dose of 1 of 2 purified (from soybeans) isoflavone preparations that delivered a genistein dose of 2, 4, 8, or 16 mg/kg body wt. These doses were higher than those previously administered to human females. Toxicity studies were performed 24 h and 3, 6, 14, and 30 d after isoflavone administration. Kinetic studies were performed during the first 24 h.

RESULTS

We observed a 7% decrease in systolic and diastolic blood pressure and a 32% decrease in the neutrophil count 24 h after treatment with formulation A. Isolated episodes of nausea, pedal edema, and breast tenderness were judged to be possibly related to the study treatment. The terminal plasma half-lives for free genistein, daidzein, and glycitein averaged 3.8, 7.7, and 3.4 h, respectively. The terminal pseudo half-lives for total genistein and total daidzein in plasma averaged 10.1 and 10.8 h, respectively. The estimated bioavailabilities of both total genistein and total daidzein from each of the 2 formulations were not significantly different.

CONCLUSIONS

A single-dose administration of purified unconjugated isoflavones at amounts that exceed normal dietary intakes had minimal clinical toxicity in healthy postmenopausal women. The pharmacokinetic data suggest that chronic dosing at 12-24-h intervals would not lead to progressive accumulation of these isoflavones.

The cardiovascular effects of soy products

In human clinical intervention trials, soy product consumption reduced levels of total cholesterol and low-density lipoprotein cholesterol (LDL-C). In October 1999, the US Food and Drug Administration approved a health claim for the relationship between consumption of soy protein and reduced risk of coronary heart disease. This article provides an overview of the cardiovascular effects of various soy products, including their effects on blood lipids, LDL-C oxidation, blood pressure, and vascular reactivity. Potential mechanisms of effect are discussed, emphasizing human clinical intervention trials. Soy consumption improves plasma lipids, although this effect appears to be more pronounced in individuals with elevated cholesterol. Soy and its associated isoflavones also reduce LDL oxidation and improve vascular reactivity.

Soy milk lowers blood pressure in men and women with mild to moderate essential hypertension

Soy-based diets reduce blood pressure in spontaneously hypertensive rats, but apparently not in hypertensive humans. In the present study, the antihypertensive potential of soy milk (500 mL twice daily) compared with cow's milk was investigated in a 3-mo double-blind randomized study of 40 men and women with mild-to-moderate hypertension. Before initiation of the study, urinary isoflavonoids (measured by HPLC) were undetectable in most cases (for genistein, they were always <100 micromol/L). After 3 mo of soy milk consumption, systolic blood pressure decreased by 18.4 +/- 10.7 mmHg compared with 1.4 +/- 7.2 mmHg in the cow's milk group (P < 0.0001), diastolic blood pressure decreased by 15.9 +/- 9.8 mmHg vs. 3.7 +/- 5.0 mmHg in the cow's milk group (P < 0.0001) and mean blood pressure decreased by 16.7 +/- 9.0 mmHg compared with 3.0 +/- 4.6 mmHg in the cow's milk group (P < 0.0001). Urinary genistein was strongly (r = -0.588) and significantly (P = 0.002) correlated with the decrease in blood pressure, particularly for diastolic values. In conclusion, chronic soy milk consumption had modest, but significant hypotensive action in essential hypertensive subjects. This hypotensive action was correlated with the urinary excretion of the isoflavonoid genistein.

Nondrug interventions in hypertension prevention and control

This review was undertaken to address the relation of various factors to HBP and their potential for preventing and controlling this widespread problem. With respect to salt intake and BP, the 1999 Workshop on Sodium and Blood Pressure of the (US) National Heart, Lung, and Blood Institute [5] will serve the reader well as a point of departure. The body of the present review provides more detailed discussion especially of recent epidemiologic research, including the DASH-Sodium trial, published more recently than the proceedings of that workshop. The DASH-Sodium trial demonstrates significant increases in SBP and DBP, with sodium intake greater than 65 mmol/d (= 3.7 g NaCl--see equivalencies in Appendix A) and with the usual American diet (versus the DASH diet). These results provide substantial evidence against current dietary practices in many populations where daily intakes of salt are much higher than recommended. We also have addressed alcohol consumption, micronutrients/macronutrients, physical activity and inactivity, obesity, cigarette smoking, and alternative approaches to treatment such as stress reduction/biofeedback, yoga/meditation, and acupuncture. Evidence for the efficacy of certain nonpharmacologic approaches to preventing and controlling HBP is strong. This evidence offers a basis for public health policies and clinical approaches that can greatly affect the incidence and consequences of HBP in the population at large. What is needed now is implementation of the policies and practices addressed here. Unless such action is taken on a large scale, we will have made poor use of the knowledge accrued over decades of research. The clinician is referred to the National Heart, Lung and Blood Institute Web site at www.nhlbi.gov/health/prof/heart/index.htm for resource and guideline information for hypertension. Patients and the general public are referred to the sister web page at www.nhlbi.gov\health\public\heart\index.htm for educational fact sheets and general information on hypertension.

Phytoestrogens in the management of the menopause: up-to-date

Despite the benefits of conventional hormone replacement therapy, some women are not candidates for this treatment and many others choose not to take it. As a result, there is growing interest among patients about natural alternatives. There is some evidence that phytoestrogens may offer protection against a wide range of human conditions, including breast cancer, cardiovascular disease, brain dysfunction, osteoporosis, and menopausal symptoms. The literature on the possible health benefits of phytoestrogens has expanded exponentially since the 1980s, mainly in response to funding initiatives by the U.S. government and soybean industries, and more lately by European and UK Ministries of Food. The physiological effects of phytoestrogens also have created a marketing opportunity that has been used by industry, particularly in soybean-producing countries such as the U.S. and Australia. Nevertheless, clinical applications for phytoestrogens are still in their infancy, and more interventional trials are required to reach definitive conclusions regarding their efficacy and safety, although they appear to represent a promising group of compounds, which may be useful in the future for the treatment of the menopausal syndrome. Also, the lack of clinical data presently available must signal caution in relation to the possible risk of adverse effects.

TARGET AUDIENCE

Obstetricians and Gynecologists, Family Physicians.

LEARNING OBJECTIVES

After completion of this article, the reader will be able to identify the various types of phytoestrogens, list the sources of phytoestrogens, and summarize the various effects of phytoestrogens.

Role of automated measurements in understanding lifestyle effects on blood pressure

Ambulatory measurements are increasingly used to evaluate the effects of different aspects of lifestyle on blood pressure. Such measurements provide greater statistical power than casual measurements and are particularly useful for assessing diurnal variations, 24-hour load and variability, and both acute and sustained effects of common behaviours. Concomitant heart rate and biochemical and genetic measurements can provide clues as to the mechanisms underlying the effects of lifestyle on blood pressure in different target populations. The information obtained is proving helpful in evaluating actions and interactions of smoking, alcohol, physical activity, caffeine consumption, various types of psychological stress, obesity, and dietary habits.

Recent developments concerning diet and hypertension

1. Recent data from randomized controlled dietary trials have shown blood pressure-lowering effects of foodstuffs and dietary patterns to be of practical importance for both individual and population blood pressure control. 2. The salient studies include Dietary Approaches to Stop Hypertension (DASH) trials, on complex dietary patterns and of additive effects of salt restriction, Trial of Nonpharmacologic Interventions in the Elderly (TONE), on weight control and sodium restriction as substitutes for drug therapy, and two Australian trials showing additive effects of dietary fish and weight control and of dietary protein and fibre in treated hypertensives. 3. Regular coffee drinking raised blood pressure in older hypertensives, whereas potential antihypertensive effects of dietary anti-oxidants require further scrutiny.

Soy for breast cancer survivors: a critical review of the literature

A variety of health benefits, including protection against breast cancer, have been attributed to soy food consumption, primarily because of the soybean isoflavones (genistein, daidzein, glycitein). Isoflavones are considered to be possible selective estrogen receptor modulators but possess nonhormonal properties that also may contribute to their effects. Concern has arisen over a possible detrimental effect of soy in breast cancer patients because of the estrogen-like effects of isoflavones. Genistein exhibits a biphasic effect on the growth of MCF-7 cells in vitro, stimulating proliferation at low concentrations but inhibiting it at high concentrations. In ovariectomized athymic mice implanted with MCF-7 cells, both genistein and soy protein stimulate tumor growth in a dose-dependent manner. In contrast, in intact mice fed estrogen, genistein inhibits tumor growth. Although two studies in premenopausal women suggested that soy exerts estrogenic-like effects on breast tissue, recently conducted year-long studies indicated that isoflavone supplements do not affect breast tissue density in premenopausal women and may decrease density in postmenopausal women. These latter effects are opposite to those of hormone replacement therapy (HRT). Importantly, substantial data suggest that the progestogen, not the estrogen, component of HRT increases risk of developing breast cancer. Furthermore, recently conducted studies have failed to find that even HRT reduces survival in breast cancer patients. Overall, the data are not impressive that the adult consumption of soy affects the risk of developing breast cancer or that soy consumption affects the survival of breast cancer patients. Consequently, if breast cancer patients enjoy soy products, it seems reasonable for them to continue to use them.

The effects of soy protein containing phytoestrogens on menopausal symptoms in postmenopausal women

OBJECTIVE

To analyze the impact of soy protein dietary supplements containing phytoestrogens on menopausal symptoms in healthy postmenopausal women.

METHODS

A double-blind, placebo-controlled trial was conducted in 94 healthy postmenopausal women aged 50-75 years, with 44 randomized to soy supplements containing 118 mg of isoflavones (daidzein, genistein, glycitein and their respective glycosides), and 50 to an identically presented casein placebo. A validated questionnaire on menopausal symptoms was administered at baseline and at 3 months of treatment. Compliance was assessed by high-performance liquid chromatography assay of urinary phytoestrogens. Statistical analysis was completed using non-parametric statistical methods and multivariate analysis.

RESULTS

At baseline 80% of women recruited were experiencing menopausal symptoms, although symptom severity was mild. Those consuming phytoestrogen supplements had 13- and 17-fold increases in urinary excretion of genistein and daidzein, respectively, with no change in the placebo group. Active soy supplements did not significantly alter either individual symptoms or specific symptom category scores when compared to placebo. Within-group comparisons revealed that the active group reported a significant improvement in vaginal dryness (p = 0.01), libido (p = 0.009), facial hair (p = 0.04) and dry skin (p = 0.027). However, similarly, those on placebo reported an improvement in libido (p = 0.015), facial hair (p = 0.014) and dry skin (p = 0.011) but not vaginal dryness.

CONCLUSIONS

In this group of 94 older postmenopausal women with a high frequency of mild menopausal symptoms, 3 months of soy supplements containing phytoestrogens did not provide symptomatic relief compared with placebo.

Selective estrogen receptor modulators in reproductive medicine and biology

Estrogen replacement therapy has significant potential benefits for postmenopausal women, such as improvement of menopausal symptoms and protection from osteoporosis, but it may also increase a woman's risk of breast cancer. Also, some women do not take hormone replacement therapy because of such undesirable side effects as breast tenderness and uterine bleeding. Therefore, there is much interest in the development of compounds that provide the benefits of estrogen replacement therapy without the risks and side effects. The selective estrogen receptor modulators make up one class of compounds with both estrogen agonist and antagonist activity. This review discusses the clinical indications, risks, benefits, and mechanisms of action of selective estrogen receptor modulators and related compounds.

Soy protein, isoflavonoids, and risk of developing coronary heart disease

The effects of soy protein and isoflavones on blood cholesterol in humans has been variable. Maximal low- density lipoprotein cholesterol lowering appears to be modest and consistently ranges from 5% to 7%. Preliminary evidence suggests a potentially beneficial effect of the isoflavone fraction of soybeans on arterial compliance. The isoflavone fraction has been demonstrated to decrease the in vitro susceptibility of low-density lipoprotein to oxidation; the significance of this finding in vivo is unknown. It is difficult to definitively say at this time whether increased consumption of soy based products will result in a decreased risk of CHD beyond their ability to displace foods high in saturated fat and cholesterol from the diet.

Isoflavonoids do not inhibit in vivo lipid peroxidation in subjects with high-normal blood pressure

The isoflavonoids genistein and daidzein have been shown to have antioxidant activity in vitro, but their effects on in vivo oxidation have not been assessed. The newly described F2-isoprostanes are believed to currently represent the best available marker of in vivo lipid peroxidation. Therefore we have assessed the effects of a 55 mg daily isoflavonoid supplement on urinary F2-isoprostane concentrations in subjects with high-normal blood pressure (BP). A total of 59 subjects completed an 8-week parallel design, randomized, double blind, and placebo-controlled study. F2-isoprostanes, isoflavonoids and creatinine were measured in 24-h urine samples taken at baseline and at the end of the intervention. There were significant increases in urinary excretion of genistein (5.22+/-0.75 mg/day, P < 0.0001) and daidzein (2.53+/-0.43 mg/day, P < 0.0001) in the group taking the isoflavonoid supplement. Creatinine excretion was significantly correlated with F2-isoprostanes at baseline (r = 0.45, P < 0.01). After adjustment for baseline values, there was no significant difference between groups in creatinine adjusted post-intervention F2-isoprostane concentrations (P = 0.74). In addition, changes in genistein and daidzein excretion were not significantly correlated with changes in F2-isoprostanes in the isoflavonoid treatment group. These results are not consistent with the suggestion that the two soy derived isoflavonoids have in vivo antioxidant activity at a level of intake achievable by dietary means and in subjects with high-normal BP.