Effects of isoflavone supplements vs. soy foods on blood concentrations of genistein and daidzein in adults

The objective of this investigation was to examine the pharmacokinetics of isoflavone concentrations over a 24-h period among healthy adults consuming either soy foods or soy isoflavone tablets at different doses. This randomized, cross-over trial was conducted with 12 generally healthy adults. The three phases of the intervention included isoflavone tablets at (1) 144 mg/day or (2) 288 mg/day and (3) soy foods designed to provide a calculated 96 mg isoflavones/day (doses in aglycone equivalents). Doses were spread out over three meals per day. After 6 days on each study phase, plasma isoflavone concentrations were determined on the seventh day at 0, 4, 8, 10, 12 and 24 h. Average levels of total isoflavone concentrations at 8, 10 and 12 h were >4 micromol/L for the soy food phase and for the higher dose tablet phase. Genistein concentrations were higher overall in the soy food vs. both the lower and the higher dose supplement phases of the study (P<.05). When comparing plasma concentrations for the two doses of tablets, saturation appeared more evident for genistein than for daidzein at the higher dose level. In conclusion, we observed important differences in the pharmacokinetics of genistein and daidzein contrasting the sources and doses of isoflavones when administered three times daily, including a possible advantage for increasing serum concentrations of isoflavones from consuming soy foods relative to isoflavone supplements.     

Absorption of isoflavones in humans: effects of food matrix and processing

If soy isoflavones are to be effective in preventing or treating a range of diseases, they must be bioavailable, and thus understanding factors which may alter their bioavailability needs to be elucidated. However, to date there is little information on whether the pharmacokinetic profile following ingestion of a defined dose is influenced by the food matrix in which the isoflavone is given or by the processing method used. Three different foods (cookies, chocolate bars and juice) were prepared, and their isoflavone contents were determined. We compared the urinary and serum concentrations of daidzein, genistein and equol following the consumption of three different foods, each of which contained 50 mg of isoflavones. After the technological processing of the different test foods, differences in aglycone levels were observed. The plasma levels of the isoflavone precursor daidzein were not altered by food matrix. Urinary daidzein recovery was similar for all three foods ingested with total urinary output of 33-34% of ingested dose. Peak genistein concentrations were attained in serum earlier following consumption of a liquid matrix rather than a solid matrix, although there was a lower total urinary recovery of genistein following ingestion of juice than that of the two other foods.     

Short-Term Soy Isoflavone Intervention in Patients with Localized Prostate Cancer: A Randomized,Double-Blind,Placebo-Controlled Trial

Purpose

We describe the effects of soy isoflavone consumption on prostate specific antigen (PSA), hormone levels, total cholesterol, and apoptosis in men with localized prostate cancer.

Methodology/Principal Findings

We conducted a double-blinded, randomized, placebo-controlled trial to examine the effect of soy isoflavone capsules (80 mg/d of total isoflavones, 51 mg/d aglucon units) on serum and tissue biomarkers in patients with localized prostate cancer. Eighty-six men were randomized to treatment with isoflavones (n = 42) or placebo (n = 44) for up to six weeks prior to scheduled prostatectomy. We performed microarray analysis using a targeted cell cycle regulation and apoptosis gene chip (GEArrayTM). Changes in serum total testosterone, free testosterone, total estrogen, estradiol, PSA, and total cholesterol were analyzed at baseline, mid-point, and at the time of radical prostatectomy. In this preliminary analysis, 12 genes involved in cell cycle control and 9 genes involved in apoptosis were down-regulated in the treatment tumor tissues versus the placebo control. Changes in serum total testosterone, free testosterone, total estrogen, estradiol, PSA, and total cholesterol in the isoflavone-treated group compared to men receiving placebo were not statistically significant.

Conclusions/Significance

These data suggest that short-term intake of soy isoflavones did not affect serum hormone levels, total cholesterol, or PSA.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00255125","term_id":"NCT00255125"}}NCT00255125     

Soy isoflavones, diet and physical exercise modify serum cytokines in healthy obese postmenopausal women

Objectives

Evaluate the effect of diet, physical exercise, and a daily oral intake of a soy isoflavones extract (Fisiogen^®) contained 200 mg of Glycine max, which corresponded to 80 mg of isoflavone (60.8 mg of genistein, 16 mg of daidzein and 3.2 mg of glicitein) on leptin and other adipokines plasma levels in healthy obese postmenopausal women.

Methods

A multicentric randomized longitudinal prospective cohort study was conducted in a sample of 87 healthy obese postmenopausal women. Patients were randomly assigned to a 1200 kcal diet and exercise group (control group) or a group of 1200 kcal diet, exercise, and daily oral intake of daily oral intake of a soy isoflavones extract (Fisiogen^®) contained 200 mg of Glycine max, which corresponded to 80 mg of isoflavone (60.8 mg of genistein, 16 mg of daidzein and 3.2 mg of glicitein) (soy isoflavones group) along 6 months. Main outcome measures were: anthropometric measures, body composition, leptin, adiponectin, TNF-alpha, homocysteine, C-reactive protein, glucose, insulin, lipid profile and oestradiol serum levels, Kupperman index and Cervantes Scale.

Results

Mean serum leptin and TNF-alpha levels declined after 6 months in both groups of the study, but only women in the soy isoflavones group showed a significant increase of mean serum levels of adiponectin.

Conclusions

Diet, physical exercise and daily oral intake of a soy isoflavones extract (Fisiogen^®) contained 200 mg of Glycine max, which corresponded to 80 mg of isoflavone (60.8 mg of genistein, 16 mg of daidzein and 3.2 mg of glicitein) have a beneficial effect on serum leptin, adiponectin and TNF-α in healthy obese postmenopausal women after 6 months of treatment.     

Comparison of the estrogenic potencies of standardized soy extracts by immature rat uterotrophic bioassay.

Soy phytoestrogens, isoflavones, are a primary class of plant-based estrogen alternatives being sold over the counter nowadays. Genistein, daidzein and glycitein are the major isoflavones found in soybeans, as aglycones and glycosides. Each isoflavone shows distinctive estrogenic activity and pharmacokinetics. Soy dry extracts, employed as pharmaceutical raw material for manufacturing isoflavone supplements, are standardized to contain 40% of total isoflavones, but the amount of each isoflavone is highly diverse. The influence of these compositional differences on the estrogenic potency of soy extracts was evaluated by uterotrophic bioassay. Five commercial samples of standardized soy dry extract, homogeneously suspended in arachis oil, were administered per os in serial doses (125-4150 mg/kg bw/day) to immature female rats for 3 days. Soy extract samples with considerable diversity in isoflavone composition revealed different estrogenic potencies. Our results indicate a need of standardization of the individual isoflavone content in soy extracts.     

Soy protein with or without isoflavones, soy germ and soy germ extract, and daidzein lessen plasma cholesterol levels in golden Syrian hamsters

Dietary isolated soy protein (ISP, containing approximately equal amounts of daidzein and genistein), ethanol-extracted ISP (ISP (-)), soygerm or soygerm extract (containing large amounts of daidzein and glycitein and little genistein) and the isoflavone, daidzein, were hypothesized to lessen plasma cholesterol in comparison with casein. Sixty male and 60 female golden Syrian hamsters (6-8 weeks of age) were randomly assigned to six treatments fed for 10 weeks. Four of the experimental diets (ISP, daidzein, soygerm, and soygerm extract) contained 1.3 mmol total isoflavones/kg. The ISP (-) diet contained 0.013 mmol isoflavone/kg, whereas the casein diet contained no isoflavones. Hamsters fed ISP, ISP (-), daidzein, soygerm, and soygerm extract had significantly less plasma total cholesterol (by 16%-28%), less non-HDL cholesterol (by 15%-50%) and less non-HDL/HDL cholesterol ratios compared with hamsters fed casein (P < 0.01). For male hamsters, there were no differences among treatments in plasma HDL concentrations. Female hamsters fed ISP (-) had significantly greater HDL levels (P < 0.01) than females fed casein or daidzein. Triglyceride concentration was significantly less in hamsters fed ISP (-) compared with the casein-fed females. Because soy protein with or without isoflavones, soygerm and soygerm extract, and daidzein lessened plasma cholesterol to an approximately equal extent, soy protein alone, varying mixtures of isoflavones, and other extractable components of soy are responsible for cholesterol-lessening effects of soy foods, mainly due to their effects to lessen LDL cholesterol.     

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.     

Effects of soy protein and isoflavone on hepatic fatty acid synthesis and oxidation and mRNA expression of uncoupling proteins and peroxisome proliferator-activated receptor gamma in adipose tissues of rats

Soy protein rich in isoflavones profoundly affects lipid metabolism in experimental animals. To distinguish the roles of the protein and isoflavone components of a soy protein preparation in regulating lipid metabolism, we compared the effects of diets containing methanol-washed soy protein low in isoflavone supplemented with a 0-, 0.5- and 4-g/kg isoflavone preparation on hepatic fatty acid metabolism and adipose tissue gene expression in rats. Diets containing soy protein irrespective of the isoflavone levels decreased the activities and mRNA expression of enzymes involved in hepatic fatty acid synthesis to similar levels. Methanol-washed soy protein compared to casein increased the mRNA expression of peroxisome proliferator-activated receptor (PPAR) alpha, and supplementing the soy protein diet with isoflavone further increased this parameter dose-dependently. However, methanol-washed soy protein compared to casein was totally ineffective in altering the activities and mRNA levels of enzymes involved in fatty acid oxidation. Supplementation of soy protein diets with isoflavone slightly increased these parameters. The mRNA level of uncoupling protein (UCP) 1 in brown adipose tissue was significantly increased and mRNA levels of UCP2 and 3, and PPARgamma2 tended to be higher in rats fed methanol-washed soy protein not supplemented with isoflavone than in the animals fed casein. Adding isoflavone to the soy protein diets dose-dependently increased these parameters. These results suggested that the protein rather than isoflavone component is primarily responsible for the physiological activity of soy protein rich in isoflavones in reducing hepatic lipogenesis. However, isoflavones may have a role in regulating heptic fatty acid oxidation and adipose tissue gene expression.     

饲喂雌鼠大豆异黄酮对后代雌性生殖性状的影响

目的研究雌性小鼠饲喂异黄酮后对其后代雌鼠生殖性状的影响。方法分别在雌鼠从断奶到妊娠前和妊娠期间两个不同阶段的日粮中添加不同剂量的大豆异黄酮（0、50、400 mg/kg）。记录F1代的出生窝产仔数、出生窝重、雌鼠的阴道最早开张时间和最早见栓时间,以及后代雌鼠性成熟期和体成熟期生殖器官重量、血清雌激素的含量。结果雌鼠妊娠期饲喂含50、400 mg/kg大豆异黄酮的饲料后F1代的窝产仔数显著高于对照组（P〈0.05）;雌鼠妊娠期采食400 mg/kg大豆异黄酮饲料,其后代雌鼠初次配种时间明显延迟（P〈0.05）;45、65日龄体重显著低于对照组,65日龄子宫重显著低于对照组,卵巢重显著高于对照组;血清中雌激素含量显著低于对照组（P〈0.05）,妊娠期间采食50 mg/kg大豆异黄酮饲料,其F1代雌鼠仅窝产仔数和45日龄时血清中雌激素含量受到影响;而雌鼠从断奶到怀孕期间饲喂含大豆异黄酮饲料的F1代在各项指标与对照组均差异无显著性。结论雌鼠妊娠期间饲喂含400 mg/kg大豆异黄酮的饲料会显著影响其雌性后代的初情期、生殖器官发育、血清雌激素含量等生殖生理性状,而在非妊娠期饲喂含大豆异黄酮饲料对F1代无显著影响。     

Role of soy isoflavones in the hypotriglyceridemic effect of soy protein in the rat

The present study was undertaken to determine whether isoflavones present in soy protein isolate contribute to the triglyceride-lowering effect of the protein relative to casein. Plasma triglyceride concentrations, their secretion rate into blood circulation, and post-heparin plasma lipoprotein lipase activity (a major determinant of intravascular catabolism of triglycerides) were measured in the fasted state in male Sprague-Dawley rats fed for 21 days one of three experimental diets varying in protein source (20% weight/weight): soy protein isolate, casein or casein to which 1.82 mg/g isoflavones (genistein and daidzein) were added to match the isoflavone content of soy protein isolate. Body weight gain was slightly lower in soy protein fed rats than in casein fed rats, but this effect was not statistically significant (P = 0.22). Casein plus isoflavones diet induced intermediary weight gain. A decrease in plasma total triglycerides was observed in rats fed soy protein and casein plus isoflavones compared with casein (P < 0.05), and there was a tendency to a positive correlation between weight gain and plasma triglyceride concentrations (r = 0.35, P = 0.06). However, no significant effect was observed on hepatic triglyceride concentrations, triglyceride secretion rate by the liver and post-heparin plasma lipoprotein lipase activity. These results show that soy protein isolate, in comparison with casein, has a hypotriglyceridemic effect in the rat and suggest that isoflavones may be responsible, at least in part, for this effect. The lowering effect of soy protein isolate and isoflavones on plasma triglyceride concentrations may be mediated by an alteration in energy balance, and possibly by the hepatic production of lipoproteins more susceptible to intravascular hydrolysis. Subtle but sustained changes in triglyceride secretion and post-heparin plasma lipoprotein lipase activity may also be implicated.     

Dietary soy isoflavone-aglycone lowers food intake in female rats with and without ovariectomy

Objective: Estrogens downregulate eating behavior, and soy isoflavones are known to be estrogenic agents. We aimed to examine whether the estrogenic property of soy isoflavones can affect food intake and body weight. Methods and Procedures: Seven‐week‐old male, female, and ovariectomized (OVX) Sprague‐Dawley rats were given free access to a diet containing 100–300 mg total isoflavone/kg diet, or to a control diet, either with or without concurrent administration of estradiol by subcutaneous implantation. Results: Dietary soy isoflavone was shown to lower food intake in female rats, whether or not the animals had undergone ovariectomy. Administration of estradiol lowered the food intake in male rats and in OVX female rats. The decrease in weekly food intake in female rats led to a reduction in their weekly gain in body weight. Dietary soy isoflavone significantly increased the concentration of serum isoflavones, especially equol (a metabolite of daidzein), regardless of gender or ovariectomy. Dietary soy isoflavone did not affect either serum estradiol concentration or uterine and didymus weights, but estradiol administration improved the uterine atrophy in OVX rats, and decreased the didymus weight in male rats. Discussion: Soy isoflavone lowers the food intake in female rats, but not in the male animals. Contrary to the hypothesis currently in vogue, the reduction in food intake caused by soy isoflavone may not be a purely estrogenic effect. This follows from the finding that the effects of soy isoflavones on food intake and on the reproductive organs differ from the corresponding effects produced by estrogen.     

Dietary isoflavones differentially induce gene expression changes in lymphocytes from postmenopausal women who form equol as compared with those who do not

Human and animal studies suggest that dietary soy isoflavones reduce cancer risk, ameliorate postmenopausal syndrome and decrease bone resorption in postmenopausal women. The capacity to form the metabolite equol from daidzein is suggested as an important modulator of response to isoflavones; this capacity depends on gut colonization with appropriate bacteria. We administered a dietary supplement containing high-dose purified soy isoflavones (genistein, 558 mg/day; daidzein, 296 mg/day; and glycitein, 44 mg/day) to 30 postmenopausal women for 84 days and collected peripheral lymphocytes at timed intervals. Using microarray analysis, we determined whether changes in gene expression associated with this treatment support existing hypotheses as to isoflavones' mechanisms of action. Expression of a large number of genes was altered by isoflavone treatment, including induction of genes associated with cyclic adenosine 3',5'-monophosphate (cAMP) signaling and cell differentiation and decreased expression of genes associated with cyclin-dependent kinase activity and cell division. We report that isoflavone treatment in subjects who have the capacity to produce equol differentially affects gene expression as compared with nonproducers, supporting the plausibility of the importance of equol production. In general, isoflavones had a stronger effect on some putative estrogen-responsive genes in equol producers than in nonproducers. Our study suggests that, in humans, isoflavone changes are related to increased cell differentiation, increased cAMP signaling and G-protein-coupled protein metabolism and increased steroid hormone receptor activity and have some estrogen agonist effects; equol-production status is likely to be an important modulator of responses to isoflavones.     

Altered testicular microsomal steroidogenic enzyme activities in rats with lifetime exposure to soy isoflavones

Androgen production in the testis is carried out by the Leydig cells, which convert cholesterol into androgens. Previously, isoflavones have been shown to affect serum androgen levels and steroidogenic enzyme activities. In this study, the effects of lifelong exposure to dietary soy isoflavones on testicular microsomal steroidogenic enzyme activities were examined in the rat. F1 male rats were obtained from a multi-generational study where the parental generation was fed diets containing alcohol-washed soy protein supplemented with increasing amounts of Novasoy, a commercially available isoflavone supplement. A control group was maintained on a soy-free casein protein-based diet (AIN93G). The diets were designed to approximate human consumption levels and ranged from 0 to 1046.6 mg isoflavones/kg pelleted feed, encompassing exposures representative of North American and Asian diets as well as infant fed soy-based formula. Activities of testicular 3β-hydroxysteroid dehydrogenase (3β-HSD), P450c17 (CYP17), 17β-hydroxysteroid dehydrogenase (17β-HSD) were assayed on post natal day (PND) 28, 70, 120, 240 and 360 while 5-reducatase was assayed on PND 28. At PND 28, 3β-HSD activity was elevated by approximately 50% in rats receiving 1046.6 mg total isoflavones/kg feed compared to those on the casein only diet. A similar increase in activity was observed for CYP17 in rats receiving 235.6 mg total isoflavones/kg feed, a level representative of infant exposure through formula, compared to those receiving 0 mg isoflavones from the casein diet. These results demonstrate that rats fed a mixture of dietary soy isoflavones showed significantly altered enzyme activity profiles during development at PND 28 as a result of early exposure to isoflavones at levels obtainable by humans.     

大豆异黄酮对雌鼠初情期等生殖性状的影响

目的通过研究大豆异黄酮对雌鼠初情期等生殖性状的影响,为母鼠的安全饲喂提供实验依据。方法本实验选用210只21日龄ICR雌鼠随机分成3组,饲喂含不同浓度大豆异黄酮（0 mg/kg、50 mg/kg、400 mg/kg）的饲料。每日检查母鼠阴道开张和阴道栓情况。采集母鼠45和65日龄时血清,利用ELISA方法检测血清中雌激素含量,并统计45、65日龄体重和子宫重。利用免疫组织化学方法检测子宫上皮雌激素受体的表达分布情况。结果雌鼠阴道开张的平均日龄分别为27.2 d、26.1 d和25.8 d,400 mg/kg组显著早于剂量为0mg/kg的对照组（P〈0.05）;雌鼠平均初次配种时间各组间差异不显著（P〉0.05）;饲养到45日龄和65日龄时400 mg/kg组雌鼠体重显著高于对照组（P〈0.05）。喂养8周后两个试验组在子宫间质细胞上雌激素受体的阳性细胞表达率显著高于对照组;在腺上皮中400 mg/kg组显著高于50 mg/kg组和对照组（0 mg/kg）;但是在腔上皮中,各组间受体的阳性细胞表达率差异不显著（P〉0.05）。结论饲喂每公斤含400 mg大豆异黄酮的饲料可以刺激初情期前母鼠阴道的开张,提高雌鼠的体重,降低65日龄时血清雌激素含量,并在饲喂8周后影响子宫间质和腺上皮上雌激素受体的表达分布;而饲喂每公斤含50 mg大豆异黄酮的饲料仅对小鼠45日龄体重及饲喂8周后子宫间质上雌激素受体的表达分布有所影响。     

A combination of soy isoflavone supplementation and exercise improves lipid profiles and protects antioxidant defense-systems against exercise-induced oxidative stress in ovariectomized rats

Menopause is often accompanied with weight gain, metabolic lipid abnormalities, and oxidative stress. In this study, we investigated the combined effects of exercise and soy isoflavone supplementation on the lipid profiles and antioxidant capacities of ovariectomized rats. Twenty-five female Sprague-Dawley rats were divided into 5 groups: sham-operated, ovariectomized (OVX), OVX with exercise (OVX+EX), OVX with soy isoflavone supplementation (OVX+ISO), and OVX with both soy isoflavones and exercise (OVX+ISO+EX). After 12 weeks of intervention, antioxidant status was evaluated in collected blood samples by the ferric reducing ability of plasma (FRAP), glutathione (GSH) content, and sodium oxide dismutase (SOD) activity. DNA damage in the lymphocytes was determined using alkaline single-cell gel electrophoresis (the Comet assay). Although there were no significant differences in weight gain and food intake, weight gain was lower in OVX+EX, OVX+ISO, and OVX+ISO+EX than in OVX. OVX+EX, OVX+ISO, and OVX+ ISO+EX showed a significant decrease in total cholesterol, triglycerides, and LDL-cholesterol compared to OVX. The soy isoflavone supplemented group had significantly increased FRAP values and GSH contents in contrast to no changes in the exercised group, whereas exercise markedly increased SOD activity and H2O2-induced DNA tail length and tail moment. Exercise with soy isoflavone supplementation significantly increased FRAP values and had no difference on SOD activity, including DNA damage. These results demonstrate that a combined treatment of moderate exercise and soy isoflavone supplementation could exert a beneficial effect on weight control and lipid profiles, and offer protection from exercise-induced oxidative stress in postmenopausal women.     

Increased aggressive behavior and decreased affiliative behavior in adult male monkeys after long-term consumption of diets rich in soy protein and isoflavones

Estrogen produced by aromatization of gonadal androgen has an important facilitative role in male-typical aggressive behavior that is mediated through its interaction with estrogen receptors (ER) in the brain. Isoflavones found in soybeans and soy-based dietary supplements bind ER and have dose- and tissue-dependent effects on estrogen-mediated responses. Yet, effects of isoflavone-rich diets on social and aggressive behavior have not been studied. We studied the effects of long-term (15 months) consumption of diets rich in soy isoflavones on spontaneous social behavior among adult male cynomolgus macaques (Macaca fascicularis) (n = 44) living in nine stable social groups. There were three experimental conditions which differed only by the source of dietary protein: casein and lactalbumin (no isoflavones), soy protein isolate containing 0.94 mg isoflavones/g protein, and soy protein isolate containing 1.88 mg isoflavones/g protein. In the monkeys fed the higher amount of isoflavones, frequencies of intense aggressive (67% higher) and submissive (203% higher) behavior were elevated relative to monkeys fed the control diet (P's < 0.05). In addition, the proportion of time spent by these monkeys in physical contact with other monkeys was reduced by 68%, time spent in proximity to other monkeys was reduced 50%, and time spent alone was increased 30% (P's < 0.02). There were no effects of treatment on serum testosterone or estradiol concentrations or the response of plasma testosterone to exogenous gonadotropin-releasing hormone (GnRH). The results indicate that long-term consumption of a diet rich in soy isoflavones can have marked influences on patterns of aggressive and social behavior.     

The effects of soy protein in women and men with elevated plasma lipids

Fifty four postmenopausal women with elevated cholesterol were recruited for a randomised, double-blind controlled trial of soy protein containing isoflavones. (ISP+) or a soy protein with a low isoflavone content (ISP-), taken daily for 12 weeks. There was an overall reduction after 12 weeks in total cholesterol (TC), LDL cholesterol (LDL-C), sex hormone binding globulin (SHBG), and luteinizing hormone (LH). There were no significant differences between treatment groups. In a separate study 27 male subjects with a TC > 5.5 mmol/l were given ISP+ for 12 weeks. In this male study there was a significant increase in HDL cholesterol (HDL-C) and SHBG. Soy protein has a cholesterol lowering effect in both women and men. These studies suggest that this effect is independent of isoflavones. Soy protein also reduces SHBG levels in both sexes.     

Transfer of Soy Isoflavone into the Egg Yolk of Chickens

A diet containing a high concentration of soy isoflavone was administered to laying hens and the contents of the isoflavones transferred to the plasma and egg yolk were measured. A method for quantitatively measuring the concentration of isoflavone in the yolk was first established, before a high concentration of soy isoflavone was administered to the laying hens over an 18-day period. The concentrations of isoflavone in the plasma and egg yolk reached their highest on the 12th day of the feeding period, the values being 3,167 nmol/l and 65.29 μg/100g, respectively. The concentration of cholesterol in the yolk was slightly affected during the early stages of the feeding period. These findings clearly demonstrate that soy isoflavone was transferred into the yolk from the feed and that the cholesterol concentration in the yolk was affected by administering the soy isoflavone-enriched feed.     

Transfer of soy isoflavone into the egg yolk of chickens.

A diet containing a high concentration of soy isoflavone was administered to laying hens and the contents of the isoflavones transferred to the plasma and egg yolk were measured. A method for quantitatively measuring the concentration of isoflavone in the yolk was first established, before a high concentration of soy isoflavone was administered to the laying hens over an 18-day period. The concentrations of isoflavone in the plasma and egg yolk reached their highest on the 12th day of the feeding period, the values being 3,167 nmol/l and 65.29 microg/100 g, respectively. The concentration of cholesterol in the yolk was slightly affected during the early stages of the feeding period. These findings clearly demonstrate that soy isoflavone was transferred into the yolk from the feed and that the cholesterol concentration in the yolk was affected by administering the soy isoflavone-enriched feed.