Effects of Dietary Intake of Soy Protein and Isoflavones on Cardiovascular Disease Risk Factors in High Risk, Middle-Aged Men in Scotland

Method development and validation for isoflavones in soy germ pharmaceutical capsules using micellar electrokinetic chromatography

The separation of six soy isoflavones (Glycitein, Daidzein, Genistein, Daidzin, Glycitin and Genistin) was approached by a 3(2) factorial design studying MEKC electrolyte components at the following levels: methanol (MeOH; 0-10%) and sodium dodecylsulfate (SDS; 20-70 mmol L(-1)); sodium tetraborate buffer (STB) concentration was kept constant at 10 mmol L(-1). Nine experiments were performed and the apparent mobility of each isoflavone was computed as a function of the electrolyte composition. A novel response function (RF) was formulated based on the production of the mobility differences, mobility of the first and last eluting peaks and the electrolyte conductance. The inspection of the response surface indicated an optimum electrolyte composition as 10 mmol L(-1) STB (pH 9.3) containing 40 mmol L(-1) SDS and 1% MeOH promoting baseline separation of all isoflavones in less than 7.5 min. The proposed method was applied to the determination of total isoflavones in soy germ capsules from four different pharmaceutical laboratories. A 2h extraction procedure with 80% (v/v) MeOH under vortexing at room temperature was employed. Peak assignment of unknown isoflavones in certain samples was assisted by hydrolysis procedures, migration behavior and UV spectra comparison. Three malonyl isoflavone derivatives were tentatively assigned. A few figures of merit for the proposed method include: repeatability (n=6) better than 0.30% CV (migration time) and 1.7% CV (peak area); intermediate precision (n=18) better than 6.2% CV (concentration); recoveries at two concentration levels, 20 and 50 microg mL(-1), varied from 99.1 to 103.6%. Furthermore, the proposed method exhibited linearity in the concentration range of 1.6-50 microg mL(-1) (r(2)>0.9999) with LOQ varying from 0.67 to 1.2 microg mL(-1). The capsules purity varied from 93.3 to 97.6%.

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.

Partial substitution of carbohydrate intake with protein intake from lean red meat lowers blood pressure in hypertensive persons

BACKGROUND

Compared with carbohydrate intake, dietary intake of plant protein can lower blood pressure in humans, but the effects of animal protein intake on blood pressure have yet to be investigated.

OBJECTIVE

We aimed to determine whether partial substitution of carbohydrate intake with animal protein intake from lean red meat changes blood pressure and other markers of cardiovascular disease risk in hypertensive persons.

DESIGN

Hypertensive persons (n = 60) were recruited to an 8-wk parallel-design study. The participants were randomly assigned either to maintain their usual diet (control group) or to partially replace energy intake from carbohydrate-rich foods with protein from lean red meat (protein group). Measurements were performed at baseline and at the end of the intervention.

RESULTS

Compared with the control group, the protein group had a significantly higher protein intake [x (95% CI) percent of energy: 5.3% (3.7%, 6.9%), P < 0.001] and a corresponding lower carbohydrate intake [-5.3% of energy (-7.9%, -2.7%), P < 0.001]. Body weight and intakes of fat, alcohol, and fiber were not significantly different between the groups. Compared with the control group, the clinic, 24-h, awake, and asleep systolic blood pressures were lower [-5.2 (-10.3, -0.1), -4.0 (-7.4, -0.6), -4.7 (-8.9, -0.5), and -4.7 (-10.3, -0.1) mm Hg, respectively, P < 0.05] and fasting plasma glucose concentrations were higher [0.33 mmol/L (0.09, 0.58 mmol/L), P = 0.008] in the protein group. These differences were independent of age, sex, and changes in weight, alcohol intake, or urinary sodium and potassium excretion. Diastolic blood pressure and heart rate, arterial compliance, blood lipids, and serum insulin were not significantly different between the groups.

CONCLUSION

Within the context of other studies, these results suggest that modest substitution of carbohydrate-rich foods with protein-rich foods may lower blood pressure in hypertensive persons.

Effect of soy- and whey protein-isolate supplemented diet on the redox parameters of trained mice

BACKGROUND

A number of clinical trials have successfully been performed using whey and/or soy proteins in the treatment of many diseases. They both have antioxidant properties, which appears to be a factor in aerobic physical performance as well. In addition, these are the most often used supplements that sportsmen take to increase their performance.

AIM OF THE STUDY

To investigate the effect of whey and soy protein supplementation on redox parameters in the muscle, on body weight, and body composition in swimming-trained and non-trained animals.

METHODS

The effect of whey and soy protein-isolate supplementation on muscle redox parameters, body weight, and body composition in trained and non-trained mice was investigated after a single exhaustive bout of exercise. Steady state free radical concentration measured using electron spin resonance (ESR) spectroscopy, reduced and oxidized glutathione ratio, thiobarbituric acid-reactive substances (TBARS), and protein carbonyl levels of the red leg muscle were measured.

RESULTS

Free radical concentrations and glutathione composition of the tissue indicated that whey protein supplementation of the regular diet was able to prevent oxidative stress regardless of training. Soy protein supplementation decreased TBARS only in the muscle of untrained animals, while training per se lowered protein damage in all investigated groups. A mixture of soy and whey protein supplementation resulted in leaner animals after training, but had no synergistic effect on either of the measured redox parameters.

CONCLUSIONS

Athletes consuming these supplements could train with higher exercise intensity. The antioxidant effect of the two proteins is based on different mechanisms of action.

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.

Use of a simplified HPLC-UV analysis for soyasaponin B determination: study of saponin and isoflavone variability in soybean cultivars and soy-based health food products

Soyasaponins are phytochemicals of major interest for health. Their identification and quantification remain difficult owing to the large number of structural isomers in soybeans and the lack of stable standards. In this study, a rapid method using high performance liquid chromatography (HPLC) using a UV detector (205 nm) was developed to identify and quantify soyasaponins belonging to group B and compare them with isoflavones in different soy materials. 2,3-Dihydro-2,5-dihydroxy-6-methyl-4H-pyran-4-one (DDMP)-conjugated soyasaponins were determined using external calibration or a molecular mass ratio after alkaline hydrolysis to cleave their DDMP moieties. The detection limit of soyasaponin I, used as a reference molecule to simplify the analysis, was 0.065 micromol/g. Soyasaponin contents in seven soybean varieties ranged from 13.20 to 42.40 micromol/g in the germ and from 2.76 to 6.43 micromol/g in the cotyledons. The within-day and between-days variation coefficients did not exceed 7.9 and 9.0%, respectively, for the major soyasaponins. Soyasaponin B quantification in different soy-based health supplements was reported along with measurements of their isoflavone content to provide information on the variability of these bioactive compounds among different types of soy food materials.

Longitudinal study of soy food intake and blood pressure among middle-aged and elderly Chinese women

BACKGROUND

Several small-scale clinical trials have suggested a potential beneficial effect of short-term soy consumption on blood pressure (BP). Data are scanty on long-term effects of the usual intake of soy foods on BP in general populations.

OBJECTIVE

Our aim was to examine the association between usual intake of soy foods and BP.

DESIGN

The usual intake of soy foods was assessed at baseline, and BP was measured 2-3 y after the baseline survey among 45 694 participants of the Shanghai Women's Health Study aged 40-70 y who had no history of hypertension, diabetes, or cardiovascular disease at recruitment. Multiple regression models were used to estimate mean differences in BP associated with various intakes of soy foods.

RESULTS

Soy protein intake was inversely associated with both systolic BP (P for trend = 0.01) and diastolic BP (P for trend = 0.009) after adjustment for age, body mass index, and lifestyle and other dietary factors. The adjusted mean systolic BP was 1.9 mm Hg lower (95% CI: -3.0, -0.8 mm Hg) and the diastolic BP was 0.9 mm Hg lower (-1.6, -0.2 mm Hg) in women who consumed > or =25 g soy protein/d than in women consuming <2.5 g/d. The inverse associations became stronger with increasing age (P for interaction < 0.05 for both BPs). Among women >60 y old, the corresponding differences were -4.9 mm Hg (95% CI: -8.0, -1.9 mm Hg) for systolic BP and -2.2 mm Hg (95% CI: -3.8, -0.6 mm Hg) for diastolic BP.

CONCLUSION

Usual intake of soy foods was inversely associated with both systolic and diastolic BPs, particularly among elderly women.

Worldwide epidemic of obesity: hope for Japanese diets

1. WHO-coordinated Cardiovascular Diseases and Alimentary Comparison Study (CARDIAC) and its follow-up, MONALISA Study covering 60 populations in 25 countries indicated an increasing prevalence of obesity, even in developing countries. 2. The index of obesity, BMI was confirmed to be related positively with both systolic and diastolic blood pressure (BP) in 60 CARDIAC populations and with the age-adjusted mortality rates of coronary heart diseases (CHD) in 25 populations where reliable demographic data were available. 3. CHD mortality rates were inversely related with biomarkers for soy bean and fish intakes, isoflavones and taurine in 24-h urine samples in 25 CARDIAC study populations. 4. Population samples were divided into two groups: soy eaters and non-eaters as well as fish eaters and non-eaters, respectively, based on WHO-CARDIAC study data. Soy eaters as well as fish eaters had significantly lower BMI, BP and serum cholesterol levels, which are three major CHD risk factors. 5. BMI was inversely related with 24-h urinary isoflavones excretion, the biomarker of soy intake and also with 24-h urinary excretion of histidine, relatively rich in fish. 6. Since both nutrients, isoflavones as phytoestrogen and histidine as the precursor of histamine may affect central appetite mechanisms, soy and fish intake may be recommended to control obesity, the major common risk of lifestyle-related diseases.