Relation between soy-associated isoflavones and LDL and HDL cholesterol concentrations in humans: a meta-analysis

Isoflavone intake in persons at high risk of cardiovascular events: implications for vascular endothelial function and the carotid atherosclerotic burden

BACKGROUND

Epidemiologic studies have suggested that a high phytoestrogen intake is inversely associated with cardiovascular disease risk factors and the incidence of cardiovascular events. However, the relation between the intake of isoflavone, a major component of phytoestrogen, and vascular endothelial function and the atherosclerotic burden remains unclear.

OBJECTIVE

We aimed to investigate the effects of various dietary soy isoflavone intakes on brachial artery flow-mediated dilation and mean maximum carotid intima-media thickness.

DESIGN

We studied 126 consecutive patients (x +/- SD age: 66.5 +/- 11.1 y; 69% male) at high risk of cardiovascular events (94% had documented coronary artery disease or stroke; 44% had diabetes). A validated food-frequency questionnaire was used to estimate their dietary intake after they achieved stable dietary patterns for 3 mo.

RESULTS

The median intakes of isoflavone and soy protein were 5.5 (range: 2.2-13.3) mg/d and 1.2 (range: 0.4-2.8) g/d, respectively. Persons in the 4th quartile of daily isoflavone intake had significantly (P < 0.05) greater flow-mediated dilation-but not mean maximum carotid intima-media thickness-than did those in the lower quartiles. After adjustment for potential confounders, a higher isoflavone intake in the 4th than in the 1st quartile (>13.3 mg/d), but not a higher intake of soy protein, predicted an absolute 2.71% increase in flow-mediated dilation (relative increase: 103%; P = 0.02) and a 0.17-mm decrease in mean maximum carotid intima-media thickness (relative decrease: 14.5%; P = 0.04).

CONCLUSION

In persons at high risk of cardiovascular events, a greater isoflavone intake is associated with better vascular endothelial function and lower carotid atherosclerotic burden.

Comparison of demography, diet, lifestyle, and serum lipid levels between the Guangxi Bai Ku Yao and Han populations

Bai Ku Yao is an isolated subgroup of the Yao minority in China. Little is known about dyslipidemia in this population. The aim of this study was to compare the effects of demography, diet, and lifestyle on serum lipid levels between the Bai Ku Yao and Han populations. A total of 1,170 subjects of Bai Ku Yao and 1,173 subjects of Han Chinese aged 15-89 years were surveyed by a stratified randomized cluster sampling. The levels of total cholesterol, high density lipoprotein cholesterol, low density lipoprotein cholesterol, apolipoprotein A-I (apoA-I), and apoB were significantly lower in Bai Ku Yao than in Han. Physical activity level and total dietary fiber intake were higher, whereas body mass index (BMI), waist circumference, total energy intake, and total fat intake were lower in Bai Ku Yao than in Han. Hyperlipidemia was positively correlated with BMI, waist circumference, and total energy and total fat intakes and negatively associated with physical activity level and total dietary fiber intake in both populations, but it was positively associated with age and alcohol consumption only in Han. The differences in the lipid profiles between the two ethnic groups were associated with different dietary habits, lifestyle choices, and levels of physical activities.

Genistein modifies liver fibrosis and improves liver function by inducing uPA expression and proteolytic activity in CCl4-treated rats

AIM

To evaluate the effect of genistein on the fibrosis and matrix degradation caused by experimentally induced fibrosis in rats.

METHODS

Hepatic fibrosis was brought about by chronic administration of carbon tetrachloride to rats. To evaluate the effect of genistein on liver fibrosis and function, total collagen content and proteolytic activity in the liver were quantified. Urokinase-type plasminogen activator (uPA) expression during experimental fibrosis was localized by immunohistochemistry. Histopathological changes were evaluated using light and electron microscopy.

RESULTS

Animals with fibrosis and treated with genistein showed an important reduction (73%) in hepatic collagen content as well as an improvement in liver function (p < 0.001). Genistein increased the capacity of the liver to degrade type I collagen and Matrigel (3.1- and 3.7-fold, respectively; p < 0.001) in animals with liver fibrosis. Genistein increased the number of uPA-immunoreactive cells. The increase in the uPA expression correlated with an increase in proteolytic activity. Histological analysis revealed a reduction in the number of fiber septa in pericentral and perisinusoidal areas. Transmission electron micrographs of livers from animals with fibrosis and treated with genistein showed a reduction in the number of hepatic stellate cells activated and a smaller number of collagen fibers.

CONCLUSION

Genistein is able to improve the liver after injury and fibrosis induced by chronic administration of carbon tetrachloride. This finding suggests that genistein has antifibrogenic potential and could therefore be useful for treating chronic liver disease.

Are soy foods protective against ischemic stroke?

Ischemic stroke is one of the leading causes of mortality and morbidity in the world. A large number of studies have observed the beneficial effects of soy protein and soy polyunsaturated fat in lowering blood cholesterol, reducing blood pressure and improving cardiovascular health. This study aims to investigate the potential of a soy food diet in the prevention of ischemic stroke through evaluation of evidence from clinical trials, meta-analyses, experimental and epidemiological studies.

Effect of soy isoflavone protein and soy lecithin on endothelial function in healthy postmenopausal women

OBJECTIVE

To assess the effects of soy isoflavone protein concentrate and soy lecithin on endothelial function, measured as flow-mediated dilation (FMD) of the brachial artery in healthy postmenopausal women.

DESIGN

This was a randomized, double-blind, placebo-controlled crossover trial with 25 participants (mean age, 61 years; body mass index, 25.46 kg/m2). The women underwent endothelial function testing at baseline and after 4 weeks of randomly assigned treatment with intervening 4-week washout periods. Treatment assignments included soy isoflavone protein (25 g/day) and soy lecithin (20 g/day), soy isoflavone protein (25 g/day) and placebo lecithin, placebo protein and soy lecithin (20 g/day), and double placebo. FMD and serum lipid levels were assessed at baseline and the end of each 4-week treatment phase.

RESULTS

Twenty-two women completed the trial. No statistically significant (P > 0.05) difference was seen in FMD between treatment groups. A trend was suggested with FMD highest after treatment with soy protein plus lecithin (7.50 +/- 9.85), followed by soy protein (5.51 +/- 10.11), soy lecithin (5.35 +/- 6.13), and lowest after placebo (4.53 +/- 7.84). Soy isoflavone protein and soy lecithin significantly increased the high-density lipoprotein/low-density lipoprotein ratio (soy isoflavone protein plus soy lecithin, 0.64 +/- 0.19, P < 0.0001; soy isoflavone protein plus placebo lecithin, 0.58 +/- 0.17, P = 0.0058; placebo protein plus soy lecithin, 0.65 +/- 0.18, P < 0.0001) relative to the baseline value (0.49 +/- 0.15).

CONCLUSIONS

In this sample of healthy postmenopausal women, soy isoflavone protein and soy lecithin significantly improved the lipid profile. A favorable influence on endothelial function could not be confirmed.

Soy isoflavones reduce electronegative low-density lipoprotein (LDL(-)) and anti-LDL (-) autoantibodies in experimental atherosclerosis

BACKGROUND

Isoflavones present in soybean may contribute to soy atheroprotective effects.

AIM OF THE STUDY

To investigate the effect of soy isoflavones supplementation on the formation of electronegative LDL (LDL(-)) and its autoantibodies in blood plasma and aortic atheromas of rabbits fed an atherogenic casein-based diet enriched with isoflavones.

METHODS

New Zealand male rabbits (n = 15) were fed an atherogenic diet (27% casein) supplemented with isoflavones (0.73 or 7.3 mg of isoflavones/kg/day, Low and High Iso groups, respectively) for 180 days. Monthly, blood samples were collected after 12-15 h fasting and at 180 days of treatment all animals were sacrificed. Isoflavones were analyzed in plasma and urine samples by HPLC. LDL(-) in plasma and atheromas was detected by ELISA and immunohistochemistry, respectively, with a monoclonal antibody reactive to LDL(-). Autoantibodies reactive to LDL(-) were analyzed in plasma and aorta by ELISA.

RESULTS

Low and High Iso groups had decreased LDL-cholesterol, increased HDL-cholesterol and lower levels of LDL(-) in blood plasma and aortic atherosclerotic lesions than the non-supplemented Control group. IgG autoantibodies reactive to LDL(- )were higher in plasma of the Control group in comparison with the High and Low Iso groups. In contrast, the aortas from animals that consumed isoflavones showed higher levels of IgG reactive to LDL(- )than the Control group.

CONCLUSION

Soy isoflavones showed hypolipidemic effects and decreased the pro-inflammatory LDL(-) subfraction in blood plasma and aorta of hypercholesterolemic rabbits.

Soy isoflavones lower serum total and LDL cholesterol in humans: a meta-analysis of 11 randomized controlled trials

BACKGROUND

Clinical trials have reported the cholesterol-lowering effects of soy protein intake, but the components responsible are not known.

OBJECTIVE

This meta-analysis was primarily conducted to evaluate the precise effects of soy isoflavones on lipid profiles. The effects of soy protein that contains enriched and depleted isoflavones were also examined.

DESIGN

PUBMED was searched for English-language reports of randomized controlled trials published from 1990 to 2006 that described the effects of soy protein intake in humans. Eleven studies were selected for the meta-analysis.

RESULTS

Soy isoflavones significantly decreased serum total cholesterol by 0.10 mmol/L (3.9 mg/dL or 1.77%; P = 0.02) and LDL cholesterol by 0.13 mmol/L (5.0 mg/dL or 3.58%; P < 0.0001); no significant changes in HDL cholesterol and triacylglycerol were found. Isoflavone-depleted soy protein significantly decreased LDL cholesterol by 0.10 mmol/L (3.9 mg/dL or 2.77%; P = 0.03). Soy protein that contained enriched isoflavones significantly decreased LDL cholesterol by 0.18 mmol/L (7.0 mg/dL or 4.98%; P < 0.0001) and significantly increased HDL cholesterol by 0.04 mmol/L (1.6 mg/dL or 3.00%; P = 0.05). The reductions in LDL cholesterol were larger in the hypercholesterolemic subcategory than in the normocholesterolemic subcategory, but no significant linear correlations were observed between reductions and the starting values. No significant linear correlations were found between reductions in LDL cholesterol and soy protein ingestion or isoflavone intakes.

CONCLUSIONS

Soy isoflavones significantly reduced serum total and LDL cholesterol but did not change HDL cholesterol and triacylglycerol. Soy protein that contained enriched or depleted isoflavones also significantly improved lipid profiles. Reductions in LDL cholesterol were larger in hypercholesterolemic than in normocholesterolemic subjects.

Effect of soy protein from differently processed products on cardiovascular disease risk factors and vascular endothelial function in hypercholesterolemic subjects

BACKGROUND

The magnitude of the effect of soy protein on lipoprotein concentrations is variable. This discordance is likely attributable to the various forms of soy protein used and to unrecognized shifts in dietary fatty acid, cholesterol, and fiber.

OBJECTIVE

The objective was to evaluate the effect of soybean processing as well as soy consumption relative to animal protein, independent of alterations in major dietary variables, on cardiovascular disease risk factors and vascular endothelial function.

DESIGN

Twenty-eight hypercholesterolemic subjects (LDL cholesterol >/=3.36 mmol/L) aged >50 y consumed each of 4 diets for 6-wk periods according to a randomized crossover design. The diets [55% of energy as carbohydrate, 30% of energy as fat, and 15% of energy as protein-7.5% of energy as experimental protein (37.5 g/d)] were designed to contain products made from either whole soybeans, soyflour, or soymilk and were compared with a diet containing an equivalent amount of animal protein (meat, chicken, and dairy products). The cholesterol, fiber, and fatty acid profiles of the diets were equalized. All food and drink were provided, and body weight was maintained throughout the study.

RESULTS

No significant differences in blood pressure, vascular endothelial function, or total cholesterol, VLDL-cholesterol, triacylglycerol, apolipoprotein B, or C-reactive protein concentrations were observed between the diets. Consumption of the soymilk diet resulted in a modest decrease (4%) in LDL-cholesterol concentrations compared with the animal-protein and soyflour diets (P < 0.05) and higher HDL-cholesterol (1%) and apolipoprotein A-I (2%) concentrations compared with the soybean and soyflour diets (P < 0.05).

CONCLUSIONS

The results suggest that the consumption of differently processed soy-based products and different types of protein (animal and soy) has little clinical effect on cardiovascular disease risk factors, including peripheral endothelial function, when other major dietary variables are held constant.

Supplementation with Soy-Protein−Rich Foods Does Not Enhance Weight Loss

The objective of this study was to determine whether a weight-loss diet high in soy-protein-rich foods leads to greater weight loss and reductions in waist circumference, fat mass, and cardiovascular disease risk factors than a control diet. Groups of overweight women (body mass index [calculated as kg/m(2)] of 28 to 33, aged 25 to 49 years) were counseled to decrease their caloric intake by 500 kcal/day for a period of 12 weeks; in addition, the soy-protein-rich group was counseled to consume 15 g soy protein/1,000 kcal daily. Soy-protein-rich foods were provided to subjects. Body weight, waist circumference, percent body fat, fat-free mass, lipids, glucose, and insulin were measured at repeated intervals. Forty-seven women completed the study. Both groups lost a similar amount of weight both when a completers only (-3.18%+/-0.63% vs -4.04%+/-0.95% for soy-protein-rich and control diets, respectively) and a last-observation-carried-forward analysis (-1.93%+/-0.50% vs -2.50%+/-0.67%, for soy-protein-rich and control diets, respectively) were performed. There was no difference between groups in change in percent fat mass (-5.31%+/-1.50% for soy-protein-rich diet vs -3.94%+/-1.68% for control diet), percent fat-free mass, and waist circumference. There was no dietary assignment-by-group interaction on lipid, glucose, and insulin concentrations when analyses were done on completers only or on all subjects using a last-observation-carried-forward approach. Percent change in any of the biochemical parameters studied over the 12-week period was not significantly different between groups. Our results do not lend support to the emerging notion that soy-protein-rich foods could be considered potential functional foods for weight management, in the quantities consumed in this study.

Effect of soy protein-containing isoflavones on lipoproteins in postmenopausal women

OBJECTIVE

Some clinical trials have demonstrated a beneficial effect of dietary soy protein on improving lipoproteins. Research also has documented that serum lipoproteins and some lipoprotein subclasses are altered as a consequence of menopause, resulting in a more atherogenic lipid profile. The purpose of this study was to determine the effects of isolated soy protein-containing isoflavones on lipoproteins and lipoprotein subclasses in both African American and white postmenopausal women with borderline to moderate low-density lipoprotein cholesterol elevations.

DESIGN

This was a randomized, double-blind, controlled clinical trial including 216 postmenopausal women. After a 4-week run-in period with a casein protein-based supplement, participants were randomly assigned to continue the casein placebo or receive soy protein-containing isoflavones for a period of 12 weeks.

RESULTS

In the soy group, the total cholesterol, low-density lipoprotein cholesterol, and low-density lipoprotein particle number decreased significantly as compared with the placebo group at 6 weeks. Although this decrease continued at 12 weeks in the soy group, the difference from the placebo group was attenuated for total cholesterol and low-density lipoprotein particle number. Multivariate analyses controlling for age, race, change in weight, change in dietary fat intake, and change in kilocalorie energy expenditure revealed that treatment remained a significant independent predictor of change in total cholesterol (P = 0.01), low-density lipoprotein cholesterol (P = 0.02), and low-density lipoprotein particle number (P = 0.002) after 6 weeks of dietary soy.

CONCLUSIONS

Increased consumption of soy protein replacing animal protein that is high in fat may help improve atherogenic lipid profiles.

Complementary and alternative therapies for the management of dyslipidemia

OBJECTIVE

To review the literature on select alternative therapies for the management of dyslipidemia.

DATA SOURCES

Searches of MEDLINE and PubMed (1965-March 2006) were conducted using the key terms omega-3-fatty acids, policosanol, plant stanols and sterols, flaxseed, red yeast rice, guggulipid, garlic, fiber, almonds, and cholesterol and/or lipids.

STUDY SELECTION AND DATA EXTRACTION

Meta-analyses, published in English and involving adults, that incorporated randomized, controlled trials on alternative therapies for dyslipidemia were reviewed. Additionally, trials published subsequent to the meta-analyses were reviewed. Articles deemed relevant were included in this review.

DATA SYNTHESIS

Of the aforementioned alternative therapies, randomized controlled trials were found for omega-3-fatty acids, policosanol, plant stanols and sterols, flaxseed, red yeast rice, guggulipid, garlic, fiber, almonds, and soy. Studies for each of these agents report varying degrees of lipid reduction. Based on published data, effective therapeutic options for lipid-lowering include intake of fiber, intake of plant stanols/sterols, replacement of animal protein with soy protein, and substitution of foods high in saturated fat with those with monounsaturated fatty acids (eg, dry roasted almonds). Adding omega-3-fatty acids is effective for reducing triglycerides in patients with hypertriglyceridemia. Well-designed studies with long-term outcome data are necessary to further define the role for guggul, red yeast rice, policosanol, garlic, and flaxseed in the management of dyslipidemia.

CONCLUSIONS

Alternative therapeutic approaches with complementary therapies are becoming increasingly popular among patients. It is important for healthcare providers to be familiar with the safety and efficacy of these agents to facilitate optimal outcomes for patients with dyslipidemia.

Soy consumption and mortality in Hong Kong: proxy-reported case-control study of all older adult deaths in 1998

OBJECTIVES

This study investigates the relation between soy consumption and mortality in a population-based case-control study in Hong Kong of all adult deaths in 1998.

METHODS

Multivariable logistic regression was used to assess the effect of soy on all-cause and cause-specific mortality in 21,494 deceased cases and 10,968 living controls who were ethnic Chinese aged 60 or above, using proxy reports collected from the person registering the death. Dietary habits were obtained from proxies in both cases and controls, based on a 7-item questionnaire.

RESULTS

The adjusted odds ratios for all-cause mortality for soy consumption 4 or more times a week compared with less than once a month were 0.77 (95% CI: 0.62, 0.95) for men and 0.66 (0.54, 0.81) for women. Mortality from lung cancer (males P = 0.02, females P = 0.02), colorectal cancer (males P = 0.07, females P < 0.001), stomach cancer (males P = 0.04, females P = 0.03), female breast cancer (P = 0.02) and ischemic heart disease (males P < 0.001, females P = 0.002) was inversely associated with soy consumption.

CONCLUSIONS

Our study suggests that maintaining traditional levels of soy consumption could be protective for some chronic diseases in China.

Diet and lifestyle recommendations revision 2006: a scientific statement from the American Heart Association Nutrition Committee

Improving diet and lifestyle is a critical component of the American Heart Association's strategy for cardiovascular disease risk reduction in the general population. This document presents recommendations designed to meet this objective. Specific goals are to consume an overall healthy diet; aim for a healthy body weight; aim for recommended levels of low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and triglycerides; aim for normal blood pressure; aim for a normal blood glucose level; be physically active; and avoid use of and exposure to tobacco products. The recommendations are to balance caloric intake and physical activity to achieve and maintain a healthy body weight; consume a diet rich in vegetables and fruits; choose whole-grain, high-fiber foods; consume fish, especially oily fish, at least twice a week; limit intake of saturated fat to <7% of energy, trans fat to <1% of energy, and cholesterol to <300 mg/day by choosing lean meats and vegetable alternatives, fat-free (skim) or low-fat (1% fat) dairy products and minimize intake of partially hydrogenated fats; minimize intake of beverages and foods with added sugars; choose and prepare foods with little or no salt; if you consume alcohol, do so in moderation; and when you eat food prepared outside of the home, follow these Diet and Lifestyle Recommendations. By adhering to these diet and lifestyle recommendations, Americans can substantially reduce their risk of developing cardiovascular disease, which remains the leading cause of morbidity and mortality in the United States.

Soy protein with and without isoflavones fails to substantially increase postprandial antioxidant capacity

Five methods for the assessment of antioxidant capacity [whole plasma conjugated diene formation, low-density lipoprotein oxidation susceptibility, ferric-reducing ability of plasma, oxygen radical absorbance capacity and perchloric-acid-treated oxygen radical absorbance capacity (PCA-ORAC)] were used in a randomized, double blind, crossover study to determine the acute postprandial antioxidant protection imparted by the isoflavone component of soy. On separate days, 16 subjects consumed one of three isocaloric shakes containing 25 g of protein in the form of soy, with 107 mg of total aglycone units of isoflavones, soy with trace isoflavones (<4 mg) or total milk protein. Blood was collected at baseline, 4 h, 6 h and 8 h after consumption. Antioxidant capacity, serum isoflavone levels, fat-soluble antioxidants and plasma vitamin C levels were evaluated. Repeated measures analysis of variance showed no significant differences (P=.05) within treatments over time in four of five antioxidant capacity measurements. Significant differences over time between the soy with trace isoflavones and the total milk protein group were observed using the PCA-ORAC assay. It can be concluded that, on an acute basis, a significant increase in serum antioxidant capacity is not detectable following consumption of soy protein.

Isoflavones made simple - genistein's agonist activity for the beta-type estrogen receptor mediates their health benefits

Soy isoflavones, the focus of much research and controversy, are often referred to as "weak estrogens". In fact, genistein is a relatively potent agonist for the recently characterized beta isoform of the estrogen receptor (ERbeta). The low nanomolar serum concentrations of unconjugated free genistein achieved with high-nutritional intakes of soy isoflavones are near the binding affinity of genistein for this receptor, but are about an order of magnitude lower than genistein's affinity for the "classical" alpha isoform of the estrogen receptor (ERalpha). Moreover, these concentrations are far too low to inhibit tyrosine kinases or topoisomerase II, in vitro activities of genistein often cited as potential mediators of its physiological effects. The thesis that these physiological effects are in fact mediated by ERbeta activation provides a satisfying rationale for genistein's clinical activities. Hepatocytes do not express ERbeta; this explains why soy isoflavones, unlike oral estrogen, neither modify serum lipids nor provoke the prothrombotic effects associated with increased risk for thromboembolic disorders. The lack of uterotrophic activity of soy isoflavones reflects the fact that ERalpha is the exclusive mediator of estrogen's impact in this regard. Vascular endothelium expresses both ERalpha and ERbeta, each of which has the potential to induce and activate nitric oxide synthase; this may account for the favorable influence of soy isoflavones on endothelial function in postmenopausal women and ovariectomized rats. The ERbeta expressed in osteoblasts may mediate the reported beneficial impact of soy isoflavones on bone metabolism. Suggestive evidence that soy-rich diets decrease prostate cancer risk, accords well with the observation that ERbeta appears to play an antiproliferative role in healthy prostate. In the breast, ERalpha promotes epithelial proliferation, whereas ERbeta has a restraining influence in this regard - consistent with the emerging view that soy isoflavones do not increase breast cancer risk, and possibly may diminish it. Premenopausal women enjoy a relative protection from kidney failure; since ERbeta is an antagonist of TGF-beta signaling in mesangial cells, soy isoflavones may have nephroprotective potential. Estrogen also appears to protect women from left ventricular hypertrophy, and recent evidence suggests that this effect is mediated by ERbeta. In conjunction with reports that isoflavones may have a modestly beneficial impact on menopausal symptoms - perhaps reflecting the presence of ERbeta in the hypothalamus - these considerations suggest that soy isoflavone regimens of sufficient potency may represent a safe and moderately effective alternative to HRT in postmenopausal women. Further clinical research is required to characterize the impact of optimal genistein intakes on endothelial and bone function in men. Studies with ERbeta-knockout mice could be helpful for clarifying whether ERbeta does indeed mediate the chief physiological effects of low nanomolar genistein. S-equol, a bacterial metabolite of daidzein, has an affinity for ERbeta nearly as high as that of genistein; whether this compound contributes meaningfully to the physiological efficacy of soy isoflavones in some individuals is still unclear.

Assessment of the longer-term effects of a dietary portfolio of cholesterol-lowering foods in hypercholesterolemia

BACKGROUND

Cholesterol-lowering foods may be more effective when consumed as combinations rather than as single foods.

OBJECTIVES

Our aims were to determine the effectiveness of consuming a combination of cholesterol-lowering foods (dietary portfolio) under real-world conditions and to compare these results with published data from the same participants who had undergone 4-wk metabolic studies to compare the same dietary portfolio with the effects of a statin.

DESIGN

For 12 mo, 66 hyperlipidemic participants were prescribed diets high in plant sterols (1.0 g/1000 kcal), soy protein (22.5 g/1000 kcal), viscous fibers (10 g/1000 kcal), and almonds (23 g/1000 kcal). Fifty-five participants completed the 1-y study. The 1-y data were also compared with published results on 29 of the participants who had also undergone separate 1-mo metabolic trials of a diet and a statin.

RESULTS

At 3 mo and 1 y, mean (+/-SE) LDL-cholesterol reductions appeared stable at 14.0 +/- 1.6% (P < 0.001) and 12.8 +/- 2.0% (P < 0.001), respectively (n = 66). These reductions were less than those observed after the 1-mo metabolic diet and statin trials. Nevertheless, 31.8% of the participants (n = 21 of 66) had LDL-cholesterol reductions of >20% at 1 y (x +/- SE: -29.7 +/- 1.6%). The LDL-cholesterol reductions in this group were not significantly different from those seen after their respective metabolically controlled portfolio or statin treatments. A correlation was found between total dietary adherence and LDL-cholesterol change (r = -0.42, P < 0.001). Only 2 of the 26 participants with <55% compliance achieved LDL-cholesterol reductions >20% at 1 y.

CONCLUSIONS

More than 30% of motivated participants who ate the dietary portfolio of cholesterol-lowering foods under real-world conditions were able to lower LDL-cholesterol concentrations >20%, which was not significantly different from their response to a first-generation statin taken under metabolically controlled conditions.

Clinical review: a critical evaluation of the role of soy protein and isoflavone supplementation in the control of plasma cholesterol concentrations

CONTEXT

The purpose of this review was to critically evaluate current research on the effect of soy protein and isoflavone supplements on plasma lipoproteins and place the potential role of soy in the prevention of coronary artery disease (CAD) into a clinical perspective.

EVIDENCE ACQUISITION

An extensive literature search was performed using a variety of medical and scientific databases including Medline, PubMed, Science Direct, Ovid, NIST, and Infotrac to identify relevant articles. Journal articles were cross-referenced for additional sources of information. Articles were evaluated based on level of experimental control as well as statistical, quantitative, and clinical analysis.

EVIDENCE SYNTHESIS

Soy and soy isoflavones have been the object of extensive research investigating their potential hypocholesterolemic effects and possible role in the prevention of CAD. It has been suggested that soy, especially the isoflavones contained in soy, improves lipoprotein levels, thus reducing the risk for CAD. This belief, however, is not uniformly accepted. Moreover, the experimental evidence in support of this notion is not as overwhelming as generally perceived, and the current available data reveal that the discrepancies observed are primarily statistical in nature rather than reflecting actual quantitative differences in the hypocholesterolemic effects detected.

CONCLUSIONS

A critical analysis of the investigations to date indicates the data are not quantitatively impressive and raises substantial questions about the clinical importance of the hypocholesterolemic effects observed.

Effects of soy protein and soybean isoflavones on thyroid function in healthy adults and hypothyroid patients: a review of the relevant literature

Soy foods are a traditional staple of Asian diets but because of their purported health benefits they have become popular in recent years among non-Asians, especially postmenopausal women. There are many bioactive soybean components that may contribute to the hypothesized health benefits of soy but most attention has focused on the isoflavones, which have both hormonal and nonhormonal properties. However, despite the possible benefits concerns have been expressed that soy may be contraindicated for some subsets of the population. One concern is that soy may adversely affect thyroid function and interfere with the absorption of synthetic thyroid hormone. Thus, the purpose of this review is to evaluate the relevant literature and provide the clinician guidance for advising their patients about the effects of soy on thyroid function. In total, 14 trials (thyroid function was not the primary health outcome in any trial) were identified in which the effects of soy foods or isoflavones on at least one measure of thyroid function was assessed in presumably healthy subjects; eight involved women only, four involved men, and two both men and women. With only one exception, either no effects or only very modest changes were noted in these trials. Thus, collectively the findings provide little evidence that in euthyroid, iodine-replete individuals, soy foods, or isoflavones adversely affect thyroid function. In contrast, some evidence suggests that soy foods, by inhibiting absorption, may increase the dose of thyroid hormone required by hypothyroid patients. However, hypothyroid adults need not avoid soy foods. In addition, there remains a theoretical concern based on in vitro and animal data that in individuals with compromised thyroid function and/or whose iodine intake is marginal soy foods may increase risk of developing clinical hypothyroidism. Therefore, it is important for soy food consumers to make sure their intake of iodine is adequate.

Soy-isoflavone-enriched foods and markers of lipid and glucose metabolism in postmenopausal women: interactions with genotype and equol production

BACKGROUND

The hypocholesterolemic effects of soy foods are well established, and it has been suggested that isoflavones are responsible for this effect. However, beneficial effects of isolated isoflavones on lipid biomarkers of cardiovascular disease risk have not yet been shown.

OBJECTIVE

The objective was to investigate the effects of isolated soy isoflavones on metabolic biomarkers of cardiovascular disease risk, including plasma total, HDL, and LDL cholesterol; triacylglycerols; lipoprotein(a); the percentage of small dense LDL; glucose; nonesterified fatty acids; insulin; and the homeostasis model assessment of insulin resistance. Differences with respect to single nucleotide polymorphisms in selected genes [ie, estrogen receptor alpha (XbaI and PvuII), estrogen receptor beta (AluI), and estrogen receptor beta(cx) (Tsp509I), endothelial nitric oxide synthase (Glu298Asp), apolipoprotein E (Apo E2, E3, and E4), cholesteryl ester transfer protein (TaqIB), and leptin receptor (Gln223Arg)] and with respect to equol production were investigated.

DESIGN

Healthy postmenopausal women (n = 117) participated in a randomized, double-blind, placebo-controlled, crossover dietary intervention trial. Isoflavone-enriched (genistein-to-daidzein ratio of 2:1; 50 mg/d) or placebo cereal bars were consumed for 8 wk, with a wash-out period of 8 wk before the crossover.

RESULTS

Isoflavones did not have a significant beneficial effect on plasma concentrations of lipids, glucose, or insulin. A significant difference between the responses of HDL cholesterol to isoflavones and to placebo was found with estrogen receptor beta(cx) Tsp509I genotype AA, but not GG or GA.

CONCLUSIONS

Isoflavone supplementation, when provided in the form and dose used in this study, had no effect on lipid or other metabolic biomarkers of cardiovascular disease risk in postmenopausal women but may increase HDL cholesterol in an estrogen receptor beta gene-polymorphic subgroup.

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.

Soy protein, isoflavones, and cardiovascular health: an American Heart Association Science Advisory for professionals from the Nutrition Committee

Soy protein and isoflavones (phytoestrogens) have gained considerable attention for their potential role in improving risk factors for cardiovascular disease. This scientific advisory assesses the more recent work published on soy protein and its component isoflavones. In the majority of 22 randomized trials, isolated soy protein with isoflavones, as compared with milk or other proteins, decreased LDL cholesterol concentrations; the average effect was approximately 3%. This reduction is very small relative to the large amount of soy protein tested in these studies, averaging 50 g, about half the usual total daily protein intake. No significant effects on HDL cholesterol, triglycerides, lipoprotein(a), or blood pressure were evident. Among 19 studies of soy isoflavones, the average effect on LDL cholesterol and other lipid risk factors was nil. Soy protein and isoflavones have not been shown to lessen vasomotor symptoms of menopause, and results are mixed with regard to soy's ability to slow postmenopausal bone loss. The efficacy and safety of soy isoflavones for preventing or treating cancer of the breast, endometrium, and prostate are not established; evidence from clinical trials is meager and cautionary with regard to a possible adverse effect. For this reason, use of isoflavone supplements in food or pills is not recommended. Thus, earlier research indicating that soy protein has clinically important favorable effects as compared with other proteins has not been confirmed. In contrast, many soy products should be beneficial to cardiovascular and overall health because of their high content of polyunsaturated fats, fiber, vitamins, and minerals and low content of saturated fat.

Hypolipidemic and antioxidant effects of Morus alba L. (Egyptian mulberry) root bark fractions supplementation in cholesterol-fed rats

The 70% alcohol extract of the Egyptian Morus alba L. root bark was fractionated over cellulose CC eluted with water, 50% methanol and finally with 100% methanol to yield 3 fractions (MRBF-1, MRBF-2 and MRBF-3), respectively. In continuation of chromatographic purification of 70% alcohol extract fractions of the Egyptian M. alba L. root bark, 4 compounds namely: mulberroside A, 5,7,2'-trihydroxyflavanone-4'-O-beta-D-glucoside and albanols A and B were isolated from MRBF-2 for the first time from the Egyptian plant. Experimentally induced atherosclerosis was produced by feeding rats a diet enriched in coconut oil (25% by weight) and cholesterol (2% by weight) for 21 days. Then, hypercholesterolemic rats were orally administered (MRBF-1, MRBF-2 and MRBF-3 fractions) in a dose of 500 mg kg(-1) day(-1) for 15 successive days, in order to evaluate their expected hypocholesterolemic activity. Lipid profile parameters such as plasma total cholesterol, LDL-C, VLDL-C, LDL:HDL ratio and triglycerides, as well as plasma and liver lipid peroxides and glutathione-S-transferase enzyme levels, serum paraoxonase enzyme level, LDL oxidation, LDL aggregation and LDL retention, were measured. Plasma and liver glutathione-S-transferase enzyme levels were unaffected in all studied groups. The results revealed that the administration of (MRBF-2 and/or MRBF-3) fractions resulted in alleviation of atherosclerotic state. Administration of MRBF-3 significantly retained plasma and liver peroxides towards their normal levels, and also, produced significant increase in resistance towards major atherogenic modifications; namely LDL oxidation, LDL aggregation and LDL retention by 44%, 30%, and 33%, respectively. Thus, it can be concluded that the consumption of MRBF-2 and (MRBF-3, in some extent) fractions of M. alba L. root bark 70% alcohol extract may act as a potent hypocholesterolemic nutrient and powerful antioxidant via the inhibition of LDL atherogenic modifications and lipid peroxides formation in hypercholesterolemic rats.

Effect of soy protein containing isoflavones on blood lipids in moderately hypercholesterolemic adults: a randomized controlled trial

BACKGROUND

Dietary intake of soy protein with isoflavones may be associated with reductions in serum cholesterol.

OBJECTIVES

To compare the effects of a water-washed soy protein concentrate with a milk-protein based control on blood lipid levels in hyperlipidemic men and women.

METHODS

A randomized, double-blind, controlled clinical trial including 159 subjects. After a 3-week run-in period during which all subjects consumed a milk protein-based supplement, participants were randomized into one of two groups: a control group (continued milk protein) and an intervention group (soy protein) for a five-week period. Fasting venous blood draws for lipid measurement were obtained at baseline, towards the end of the run-in period and at the end of the intervention. Blood isoflavone concentrations were measured at the end of the study.

RESULTS

Blood lipid levels were not significantly different between groups at any point in time; and there were no significant associations between blood isoflavones and lipid levels. Significant decreases in total cholesterol (19 mg/dL), and LDL-cholesterol (11 mg/dL), were observed during the run-in period, with no further decreases in lipids during the intervention period in either group.

CONCLUSIONS

These results do not support the hypothesis that water-washed soy protein has an effect on blood lipids. Several hypotheses are discussed, highlighting the selective nature of the effect of soy consumption in the population. The cholesterol-lowering effect during the run-in period may be explained by the "regression to the mean effect" and by other factors related to study participation, mainly nutrient displacement induced by the protein supplement.

Effects of soy supplementation on blood lipids and arterial function in hypercholesterolaemic subjects

BACKGROUND

Studies on soy supplementation suggest a cardioprotective potential.

OBJECTIVE

To examine the effects on LDL cholesterol and arterial function as a result of dietary enrichment with soy supplementation.

DESIGN

A Randomized, double blind, parallel intervention trial.

SETTING

Department of Endocrinology and Metabolism C, Aarhus University Hospital, and Department of Human Nutrition, The Royal Veterinary and Agricultural University, Denmark.

SUBJECTS

In all, 100 hypercholesterolaemic but otherwise healthy subjects were included in the study of which 89 completed it.

INTERVENTIONS

Subjects were randomly assigned to 24 weeks of daily intake of either a soy supplement, Abalon (30 g soy protein, 9 g cotyledon fibre and 100 mg isoflavones) or placebo (30 g of casein). The soy supplement and placebo were provided in two sachets daily that were stirred in water. Fasting plasma lipids, TNF-alpha, homocysteine, insulin sensitivity, homeostasis model assessment (HOMA-IR), serum insulin, serum glucose, blood pressure as well as Glucagon-like peptide 1 (GLP-1), glucose-dependent insulinotropic peptide (GIP) and plasma lipids to a fat-rich meal were recorded before and after the intervention. In a sub study in 32 subjects, arterial dilatory capacity, compliance, and distensibility were recorded before and after the intervention.

RESULTS

In the main study, no difference in fasting plasma lipid levels or insulin sensitivity was found between soy-based supplement and placebo. A significant postprandial increase in GIP to the meal test was observed in the soy group (P < 0.05). In a substudy, no difference between the groups in changes in flow-mediated vasodilatation (P = 0.84) was detected, while the soy supplementation caused a reduction in LDL and total cholesterol.

CONCLUSIONS

No significant effects on blood lipids were observed in the main study to a soy supplementation in hypercholesterolaemic subjects after 24 weeks. In the substudy, the soy supplementation, however, reduced LDL and total cholesterol but did not influence markers of arterial function.

Soy protein reduces hepatic lipotoxicity in hyperinsulinemic obese Zucker fa/fa rats

Hepatic steatosis is commonly present during the development of insulin resistance, and it is a clear sign of lipotoxicity attributable in part to an accelerated lipogenesis. There is evidence that a soy protein diet prevents the overexpression of hepatic sterol-regulatory element binding protein-1 (SREBP-1), decreasing lipid accumulation. Therefore, the aim of the present work was to study whether a soy protein diet may prevent the development of fatty liver through the regulation of transcription factors involved in lipid metabolism in hyperinsulinemic and hyperleptinemic Zucker obese fa/fa rats. Serum and hepatic cholesterol and triglyceride levels, as well as VLDL-triglyceride and LDL-cholesterol, were significantly lower in rats fed soy protein than in rats fed a casein diet for 160 days. The reduction in hepatic cholesterol was associated with a low expression of liver X receptor-alpha and its target genes, 7-alpha hydroxylase and ABCA1. Soy protein also decreased the expression of SREBP-1 and several of its target genes, FAS, stearoyl-CoA desaturase-1, and delta5 and delta6 desaturases, decreasing lipogenesis even in the presence of hyperinsulinemia. Reduction in SREBP-1 was not associated with the presence of soy isoflavones. Finally, soy protein reduced SREBP-1 expression in adipocytes, preventing hypertrophy, which also helps prevent the development of hepatic lipotoxicity.

Dietary protein type and cardiovascular disease risk factors

Observational studies suggested a negative association between vegetable protein and cardiovascular disease risk, whereas intervention studies have been less consistent. The majority of interventional studies that have evaluated the effects of soy protein compared to animal protein have used casein. Relative to casein, the effect of soy protein on lipids and lipoprotein appears to be variable and less dramatic than originally reported. When compared to animal proteins other than casein, relatively large intakes of soy protein (>/=25 g/d) appear to have a consistent, albeit small ( asymptotically equal to 5%), hypocholesterolemic effect. When assessed, no consistent additional benefit of soy protein on other cardiovascular disease risk factors; Lp(a), inflammatory markers, biomarkers of oxidative stress and endothelial function, has been reported. The data available on the effect of dietary protein on plasma lipids, lipoprotein levels, and cardiovascular disease risk factors is difficult to interpret and insufficient to account for the discrepancy between the observational and interventional studies.

Comparison of regulative functions between dietary soy isoflavones aglycone and glucoside on lipid metabolism in rats fed cholesterol

The effects of dietary soy isoflavones aglycone and glucoside on lipid metabolism were compared in male Sprague-Dawley rats (4 weeks old) given purified diets containing 0.3% cholesterol. The rats were fed a diet supplemented with either isoflavone aglycone-rich powder (IF-A group) or isoflavone glucoside-rich powder (IF-G group) or isoflavone-free diet (control group) for 40 days. The additional level of isoflavone aglycone moiety in the diet was prepared to the same level (approximately 0.096 g/100 g: approximately 0.1% in diet). The activity of hepatic cholesterol 7alpha-hydroxylase tended to be slightly higher in the rats fed isoflavones than in those fed the isoflavone-free diet. On the other hand, the activity of hepatic Delta6 desaturase in the IF-A group was lower than that of the control group. Reflecting this effect, the Delta6 desaturation indices [(20:3n-6+20:4n-6)/18:2n-6] in liver phospholipids of the IF-A group were lower than those in the control group. Liver and serum total cholesterol levels and liver TG level were also reduced by consumption of isoflavone aglycone. Moreover, serum TG level was lowered by consumption of both isoflavones aglycone and glucoside. The level of serum total isoflavones in the IF-A group was significantly higher than that in the IF-G group. Therefore, we speculate that the absorption speed of isoflavone aglycones might be faster than that of isoflavone glucosides in rats. This study suggests that dietary soy isoflavones, particularly their aglycone form, may exert a beneficial effect on lipid metabolism in rats fed cholesterol.

Polyphenols and prevention of cardiovascular diseases

PURPOSE OF REVIEW

Polyphenols are the most abundant dietary antioxidants and research on their role in the prevention of degenerative diseases has developed quickly over these last few years. This paper reviews the recent studies on the prevention of cardiovascular diseases by polyphenols, focusing on human studies.

RECENT FINDINGS

A large number of recent intervention studies have shown that several biomarkers of cardiovascular risk are influenced by the consumption of polyphenol-rich foods. Effects on biomarkers of oxidative stress, lipemia and inflammation appear so far inconclusive. More consistent effects have been observed on endothelial function and haemostasis and support a reduction of risk by polyphenols in agreement with the few epidemiological studies already published. All clinical studies have used foods or beverages containing a mixture of different polyphenols and the exact nature of the most active compounds remains largely unknown. Absorption, metabolism and elimination vary widely between polyphenols. These data on bioavailability should be taken into account to improve the experimental design and the interpretation of the observed effects.

SUMMARY

Future intervention studies should include a detailed assessment of the bioavailability of polyphenols. Beyond clinical trials carried out with polyphenol-rich foods, more studies with pure polyphenols will also be needed to establish their role in the prevention of cardiovascular diseases.

Regulation of gene transcription by botanicals: novel regulatory mechanisms

Early investigations of gene regulation revealed that nutrients could modulate gene expression, an example being the discovery of metal-regulated gene transcription ( 11, 19, 44). Only more recently have we focused on the ability of non-nutritional botanicals or functional food components to affect gene expression at the transcriptional level. Significant findings include the discovery that hyperforin is an active ingredient of the herbal remedy St. John's wort, and activates gene transcription of cytochrome p450-3A4, causing significant botanical-drug interactions. Recently, the lipid-regulating peroxisome proliferator-activated receptors have been studied as receptors activated by soy isoflavones, perhaps explaining the lipid-lowering effect of soy intake. Epigallocatechin gallate has been shown to be an inhibitor of the protealytic activity of the proteasome; this inhibition has a significant implication for cell proliferation and the stability of transcription factors in the nucleus. Very recently, the effects of botanicals have been studied as activators of sirtuins, important deacetylation enzymes that have been shown to enhance lifespan in a variety of organisms. Sirtuins have been implicated in the lifespan-enhancing effect of caloric restriction. Originally presumed to act mainly on compaction or accessibility of DNA, recent evidence shows important activity of sirtuins as controllers of transcriptional coactivator availability. This review focuses on novel mechanisms by which botanical products regulate cell function via gene transcription. Investigating these newly appreciated mechanisms will assist with the characterization and clarification of specific effects of botanicals on gene expression.

A Dietary portfolio: Maximal reduction of low-density lipoprotein cholesterol with diet

Over the past two decades, cholesterol-lowering drugs have proven to be effective and have been found to significantly reduce the risk of coronary heart disease (CHD). However, diet and lifestyle factors are still recognized as the first line of intervention for CHD risk reduction by the National Cholesterol Education Program and the American Heart Association, which now advocate use of viscous fibers and plant sterols, and soy protein and nuts, respectively. In a series of metabolically controlled studies, we have combined these four cholesterol-lowering dietary components in the same diet (ie, a dietary portfolio of cholesterol-lowering foods) in an attempt to maximize low-density lipoprotein cholesterol reduction. We have found that the portfolio diet reduced low-density lipoprotein cholesterol by approximately 30% and produced clinically significant reductions in CHD risk. These reductions were the same as found with a starting dose of a first-generation statin drug.

Soy intake and blood cholesterol concentrations: a cross-sectional study of 1033 pre- and postmenopausal women in the Oxford arm of the European Prospective Investigation into Cancer and Nutrition

BACKGROUND

Clinical trials have suggested that the intake of soy protein reduces blood cholesterol. Few studies have explored this relation in subjects who consume soy as part of their regular diet.

OBJECTIVE

In this study, we investigated whether blood cholesterol concentrations are related to the intake of soyfoods in a cohort comprising subjects with a wide variation in soy intake.

DESIGN

This cross-sectional study included 1033 pre- and postmenopausal women selected from the Oxford arm of the European Prospective Investigation into Cancer and Nutrition. The sample included 361 nonvegetarians, 570 vegetarians, and 102 vegans. Their dietary intake was assessed by using a food-frequency questionnaire. Anthropometric data, medical history, and lifestyle information were obtained with the use of a questionnaire, blood samples were obtained, and plasma total, LDL-, and HDL-cholesterol concentrations were measured.

RESULTS

Soy-protein intake was inversely associated with total and LDL-cholesterol concentrations and with the ratio of total to HDL cholesterol but not with HDL-cholesterol concentrations. Mean plasma LDL-cholesterol concentrations in women with a soy-protein intake >/=6 g/d was 12.4% lower than that in women who consumed <0.5 g/d (P < 0.001).

CONCLUSION

Moderate intakes of soyfoods as part of a regular diet are associated with favorable blood cholesterol concentrations.

Skeletal benefits of soy isoflavones: a review of the clinical trial and epidemiologic data

PURPOSE OF REVIEW

Osteoporosis is a worldwide problem of immense magnitude that is expected to worsen in many countries with aging populations. Consequently, there is a need to identify ways to reduce the risk of developing this disease. This is especially true in light of clinical trial data showing the long-term harm of conventional hormone therapy outweighs the benefits. It is well established that many dietary components impact the skeletal system; in this regard there is particular interest in the possible skeletal benefits of soybean isoflavones. The purpose of this review is to evaluate the clinical and epidemiologic studies relevant to the hypothesis that isoflavones promote bone health.

RESULTS

Fifteen clinical trials were identified that examined the effects of isoflavones or isoflavone-rich soy protein on bone mineral density. Most trials were conducted for 1 year or less and involved relatively few (<30) participants per group. The findings from these studies are inconsistent but generally suggest that isoflavones reduce bone loss in younger postmenopausal women. Similarly, the limited epidemiologic data generally show that among Asian populations isoflavone intake is associated with higher bone mineral density. The clinical data suggest that approximately 80 mg/day isoflavones are needed to derive skeletal benefits whereas the epidemiologic data suggest lower amounts are efficacious.

SUMMARY

Until more definite data are available, although soy foods and isoflavones can not be viewed as substitutes for established anti-osteoporotic medications health professionals can feel justified in encouraging postmenopausal women concerned about bone health to incorporate soyfoods into their diet.

Soy isoflavone intake lowers serum LDL cholesterol: a meta-analysis of 8 randomized controlled trials in humans

Clinical trials have noted hypocholesterolemic effects of soy protein intake, but the components responsible are not known. This meta-analysis of 8 randomized controlled trials was conducted to more precisely evaluate the effects of isoflavones on blood LDL cholesterol concentration independently of soy protein level. PubMed was searched for English-language "randomized controlled trial" articles published from 1966 to 2003 that described the effects of soy protein isolate (SPI) intake with measured isoflavone levels on blood lipids in humans using the search terms "soy protein," "isoflavones," and "cholesterol." From 31 articles identified by the search, 8 articles (with 10 low vs. high isoflavone comparisons) were selected for the meta-analysis. Subjects in each comparison consumed similar dietary fat, cholesterol, and fiber; the reported body weight of subjects did not change significantly during treatment. Serum LDL cholesterol concentration in subjects who consumed SPI (mean 50 g/d) with high isoflavone content (mean intake 96 mg/d) decreased by 0.15 mmol/L (95% CI: 0.08 to 0.23 mmol/L; P < 0.0001) compared with those who consumed the same SPI level with low isoflavone content (mean intake 6 mg/d). Decreases in serum LDL cholesterol concentration in hypercholesterolemic and normocholesterolemic subjects were 0.18 mmol/L (95% CI: 0.01 to 0.35 mmol/L; P = 0.03) and 0.14 mmol/L (95% CI: 0.06, 0.23 mmol/L; P = 0.0008), respectively. With identical soy protein intake, high isoflavone intake led to significantly greater decreases in serum LDL cholesterol than low isoflavone intake, demonstrating that isoflavones have LDL cholesterol-lowering effects independent of soy protein.

Antioxidant activities and lipid lowering effects of isoflavone in male rabbits

Dietary flavonoids appear to play a role in the prevention of a number of chronic diseases such as cancer and cardiovascular disease and the soy isoflavones have been the focus of particular. Consumption of soy isoflavones may reduce the risk of cardiovascular disease both through reduction in serum lipids and by the antioxidant properties. We have therefore investigate the effects of either 2.5 or 5 mg/kg B.W. doses of isoflavones on the levels of free radicals, lipids and lipoproteins in male New Zealand White rabbits. Animals were orally given 2.5 or 5 mg/kg B.W. doses of isoflavones. The tested doses were given to rabbits every other day for 13 weeks. Treatment with isoflavones caused significant (P<0.05) decrease in the concentrations of free radicals in plasma by 33% and 35%, liver by 18% and 27%, brain by 12% and 33%, testes by 40% and 21%, and kidney by 38% and 20% for 2.5 or 5 mg/kg B.W. doses, respectively, as compared to the control. On the other hand, the activity of glutathione S-transferase (GST) did not change in treated animals as compared to control. Also, results showed that isoflavones caused a significant decrease (P<0.05) in the levels of plasma total lipids (TL) by 16% and 19%, total cholesterol by 20% and 20%, triglyceride (TG) by 18% and 23%, low density lipoprotein (LDL) by 19%, 22%, very low density lipoprotein (VLDL) by 18% and 23%, and LDL:HDL ratio by 36% and 39% for 2.5 or 5 mg/kg B.W. doses, respectively, as compared to the control. While the level of high density lipoprotein (HDL) increased by 29% and 32%. The present results showed that the 5 mg/kg dose of isoflavone seemed to be related to a better plasma lipid and lipoprotein profiles and antioxidant activity.

Isoflavone genistein: photoprotection and clinical implications in dermatology

Genistein is a soybean isoflavone with diverse biological activities. It is a potent antioxidant, a specific inhibitor of protein tyrosine kinase, and a phytoestrogen. In recent years, increasing evidence has accumulated that this natural ingredient shows preventative and therapeutic effects for breast and prostate cancers, postmenopausal syndrome, osteoporosis, and cardiovascular diseases in animals and humans. In the past decade we have conducted a series of studies and demonstrated that genistein has significant antiphotocarcinogenic and antiphotoaging effects. Genistein substantially inhibits skin carcinogenesis and cutaneous aging induced by ultraviolet (UV) light in mice, and photodamage in humans. The mechanisms of action involve protection of oxidative and photodynamically damaged DNA, downregulation of UVB-activated signal transduction cascades, and antioxidant activities. In this article, we review the biological activities of genistein, as well as published and unpublished research from our laboratory. In addition, we discuss the potential application of genistein to clinical dermatology.