Soy Consumption Research Articles

Short Term Effects on Bone Quality Associated with Consumption of Soy Protein Isolate and Other Dietary Protein Sources in Rapidly Growing Female Rats

Beneficial effects of soy protein consumption on bone quality have been reported. The effects of other dietary protein sources such as whey protein hydrolysate (WPH) and rice protein isolate (RPI) on bone growth have been less well examined. The current study compared effects of feeding soy protein isolate (SPI), WPH and RPI for 14 d on tibial bone mineral density (BMD) and bone mineral content (BMC) in intact and ovariectomized (OVX) rapidly growing female rats relative to animals fed casein (CAS). The effects of estrogenic status on responses to SPI were also explored. Tibial peripheral quantitative computerized tomography (pQCT) showed all three protein sources had positive effects on either BMD or BMC relative to CAS (P < 0.05), but SPI had greater effects in both intact and OVX female rats. SPI and E2 had positive effects on BMD and BMC in OVX rats (P < 0.05). However, trabecular BMD was lower in a SPI + E2 group compared to a CAS + E2 group. In OVX rats, SPI increased serum bone formation markers, and serum from SPI-fed rats stimulated osteoblastogenesis in ex vivo. SPI also suppressed the bone resorption marker RatLaps (P < 0.05). Both SPI and E2 increased alkaline phosphatase gene expression in bone, but only SPI decreased receptor activator of nuclear factor-kappaB ligand (RANKL) and estrogen receptor gene expression (P < 0.05). These data suggest beneficial bone effects of a soy diet in rapidly growing animals and the potential for early soy consumption to increase peak bone mass.

Study of histo-metrical changes in the knee joint in mice following consumption of soya

To examine the effect of oral preparation of soya on the development of knee joint histopathology in mice model. For this study, a total number of frothy female mice three weeks age were used. The female mouse were divided in to four groups The first group received food with low amount of protein (%0 soya), second group received food with adequate amount of protein (%0 soya), third group received food with adequate amount of protein (%20 soya) and forth group received food with adequate amount of protein (%40 soya).Histological sections from the medial and lateral tibial condoyles were prepared from all joint. Computerized image analysis showed significant histological differences by soya. In treated animals showed increase the thickness and cell numbers of cartilage (p

Soy consumption for reduction of menopausal symptoms

To review current research on the effects of soy consumption on menopausal symptoms. To review results of recent meta-analyses and individual clinical trials. One recent meta-analysis reported that isoflavone supplementation was associated with a 34% reduction in hot flashes, with increased efficacy as the baseline number of flashes and isoflavone dose increased. A second review concluded that consumption of at least 15 mg genistein, rather than total isoflavones, is responsible for the reduction in symptoms. Results of these two reviews are supported by most subsequent randomized controlled trials. Consumption of 30 mg/day of soy isoflavones (or at least 15 mg genistein) reduces hot flashes by up to 50 %. This total reduction includes that provided by "the placebo effect". The greatest benefit may be realized when the isoflavone-rich food or supplement is taken in divided doses by subjects who experience at least four hot flashes/day.

Urinary Isoflavones Are Increased in Adults, But Decreased in Children, Consuming Soy When on Oral Antibiotic Therapy

The goal of this study was to evaluate how oral antibiotics (OABX) change the appearance of isoflavones (IFLs) in adults and children after soy consumption. The urinary IFL excretion rate (UIER) known to reflect circulating IFLs was hypothesized to change due to intestinal microflora changes by OABX. Subjects provided urine collections in pairs of a baseline urine and an overnight urine before and after consuming soy nuts first during OABX treatment and then again when healthy. During OABX versus when healthy, UIER (nmol/h/kg) in adults (n = 12) was increased (P < 0.05) for daidzein (35.2 ± 7.2 vs. 18.9 ± 2.4), daidzein + genistein + glycitein [nonmetabolites (NM); 42.6 ± 8.0 vs. 23.6 ± 2.9), and total isoflavonoids (Total IFLs; daidzein + genistein + glycitein + dihydrodaidzein + dihydrogenistein + equol + O-desmethylangolensin) (51.5 ± 10.3 versus 29.6 ± 4.7). In contrast, children (n = 7) showed reduced UIER (P < 0.05) when on OABX versus when healthy for daidzein (36.3 ± 6.4 vs. 46.8 ± 4.7), dihydrodaidzein (1.2 ± 0.6 vs. 3.0 ±1.1), NM (46.3 ± 8.2 vs. 59.5 ± 6.0), dihydrodaidzein + dihydrogenistein + equol + O-desmethylangolensin (1.0 ± 0.8 vs. 4.3 ± 1.3), and Total IFLs (48.2 ± 8.5 vs. 63.8 ± 6.4).

The Effects of Soy Isoflavones on Obesity

Over the last decades, the prevalence of obesity and related diseases has increased rapidly in the Western world. Obesity is a disorder of energy balance and is associated with hyper-insulinemia, insulin resistance, and abnormalities in lipid metabolism, and it is one of the most important risk factors in the development of Type II diabetes, cardiovascular disease, atherosclerosis, and certain cancers. Because of the lower frequency of these diseases in Asian countries, attention has been turned toward the Asian diet, which consists highly of soy and soy-based products. The health benefits associated with soy consumption have been linked to the content of isoflavones, the main class of the phytoestrogens. As a result of their structural similarities to endogenous estrogens, isoflavones elicit weak estrogenic effects by competing with 17beta-estradiol (E2) for binding to the intranuclear estrogen receptors (ERs) and exert estrogenic or antiestrogenic effects in various tissues. The estrogenic activities of soy isoflavones are thought to play an important role in their health-enhancing properties. Additionally, the isoflavones have been proved to exert non-ER-mediated effects through numerous other pathways. Genistein, daidzein, and glycitein are the principal isoflavones in soy. Genistein is the most thoroughly examined of these, because it is the most prevalent isoflavone in soy and the most active of these compounds, because of its higher binding affinity for the ER. Genistein and daidzein can be obtained in high levels in humans under certain nutritional conditions, and epidemiologic and laboratory data suggest that these compounds could have health benefits in human obesity. This review will focus on the latest results of research on isoflavones and their effect on obesity in cell cultures, rodents, and humans.

Group B Saponins in Soy Products in the U.S. Department of Agriculture—Iowa State University Isoflavone Database and Their Comparison with Isoflavone Contents

Isoflavones in soy protein foods are thought to contribute to the cholesterol-lowering effect observed when these products are fed to humans. The group B saponins are another ethanol-soluble phytochemical fraction associated with soy proteins and isoflavones and have also been associated with cholesterol-lowering abilities. We measured the group B soyasaponin concentrations in a variety of soy foods and ingredients in the U.S. Department of AgricultureIowa State University Isoflavone Database. We compared the isoflavone and soy saponin concentrations and distributions in intact soybeans, soy ingredients, and retail soy foods. Group B saponins occur in six predominant forms. There appears to be no correlation between saponin and isoflavone concentrations in intact soybeans ranging from 5 to 11 mumol isoflavones/g soybean and from 2 to 6 mumol saponin/g soybean. Depending upon the type of processing, soy ingredients have quite different saponins/isoflavones as compared to mature soybeans. In soy foods, the saponin:isoflavone ration ranges from 1:1 to 2:5, whereas in soy protein isolates, the ratio is approximately 5:3. Ethanol-washed ingredients have very low saponins and isoflavones. These very different distributions of saponins and isoflavones in soy products may affect how we view the outcome of feeding trials examining a variety of protective effects associated with soy consumption.

Investigating the Optimal Soy Protein and Isoflavone Intakes for Women: A Perspective

Traditional soyfoods have been consumed for centuries throughout much of East Asia and, recently, these foods have also become popular in the West. Soyfoods and specific soybean components, such as the protein and isoflavones, have attracted attention for their possible health benefits. Isoflavones are classified as phytoestrogens and have been postulated to be natural alternatives to hormone therapy for menopausal women. To provide guidance on optimal soy intake, this article evaluates Asian soy consumption and both clinical and Asian epidemiologic studies that examined the relationship between soy intake and a variety of health outcomes. On the basis of these data and the standard principles of dietary practice the author suggests that optimal soy protein and isoflavone intakes are 15-20 g/day and 50-90 mg/day, respectively. In addition, an intake of 25 g/day soy protein can be specifically used as the recommendation for cholesterol reduction.

High Tofu Intake Is Associated with Worse Memory in Elderly Indonesian Men and Women

Background/Aims: Cell culture studies suggest that phytoestrogens, abundant in soy products such as tempe and tofu, could protect against cognitive decline. Paradoxically, the Honolulu Asia Aging Study reported an increased risk for cognitive impairment and other dementia markers with high tofu (soybean curd) intake. Methods: A cross-sectional study was carried out in 2 rural sites (Borobudur and Sumedang) and 1 urban site (Jakarta) among mainly Javanese and Sundanese elderly (n = 719, 52–98 years of age). Memory was measured using a word learning test sensitive to dementia and soy consumption was assessed using Food Frequency Questionnaire items. Results: High tofu consumption was associated with worse memory (β = –0.18, p < 0.01, 95% CI = –0.34 to –0.06), while high tempe consumption (a fermented whole soybean product) was independently related to better memory (β = 0.12, p < 0.05, 95% CI = 0.00–0.28), particularly in participants over 68 years of age. Fruit consumption also had an independent positive association. The analyses were controlled for age, sex, education, site and intake of other foods. Conclusion: The results for tofu consumption as a risk factor for low memory function may tie in with the Honolulu Asia Aging Study data. It is unclear whether these negative associations could be attributed to potential toxins or to its phytoestrogen levels. Estrogen (through which receptors phytoestrogens can exert effects) was found to increase dementia risk in women over 65 years of age. Tempe contains high levels of phytoestrogens, but (due to fermentation) also exhibits high folate levels which may exert protective effects. Future studies should validate these findings and investigate potential mechanisms.

Polymorphisms of IFS1 and IFS2 gene are associated with isoflavone concentrations in soybean seeds

Soybean isoflavones are associated with many health benefits of soy consumption, and isoflavone levels are one of the most important output traits of soybean. Isoflavones are synthesized from the phenylpropanoid pathway. Isoflavone synthase (IFS) acts as the key metabolic entry point for the formation of all kinds of isoflavones. We have cloned, sequenced, and analyzed the IFS1 and IFS2 genomic regions from 33 Chinese soybean accessions including 16 Glycine soja and 17 Glycine max. The isoflavone levels in these accessions vary greatly, ranging from 536.6 μg/g to 5509.1 μg/g dry seed weight. High nucleotide diversity and low extent of linkage disequilibrium (LD) in these two genes provided sufficient genetic resolution for association analysis of polymorphisms in these genes and soybean seed isoflavone levels. As a result, three single nucleotide polymorphisms (SNPs) in IFS1 gene and two SNPs in IFS2 gene were found closely associated ( P < 0.05) with all individual and total isoflavone levels in seeds, regardless of population structure. These results indicated that IFS1 and IFS2 gene both contributed to the levels of isoflavones in seeds. These polymorphisms may serve as important molecular markers for breeding.

Health Effects of Soy Protein and Isoflavones in Humans

Epidemiological investigations suggest that soy consumption may be associated with a lower incidence of certain chronic diseases. Clinical studies also show that ingestion of soy proteins reduces the risk factors for cardiovascular disease. This led to the approval of the food-labeling health claim for soy proteins in the prevention of coronary heart disease by the U.S. FDA in 1999. Similar health petitions for soy proteins have also been approved thereafter in the United Kingdom, Brazil, South Africa, the Philippines, Indonesia, Korea, and Malaysia. However, the purported health benefits are quite variable in different studies. The Nutrition Committee of the American Heart Association has assessed 22 randomized trials conducted since 1999 and found that isolated soy protein with isoflavones (ISF) slightly decreased LDL cholesterol but had no effect on HDL cholesterol, triglycerides, lipoprotein(a), or blood pressure. The other effects of soy consumption were not evident. Although the contributing factors to these discrepancies are not fully understood, the source of soybeans and processing procedures of the protein or ISF are believed to be important because of their effects on the content and intactness of certain bioactive protein subunits. Some studies have documented potential safety concerns on increased consumption of soy products. Impacts of soy products on thyroid and reproductive functions as well as on certain types of carcinogenesis require further study in this context. Overall, existing data are inconsistent or inadequate in supporting most of the suggested health benefits of consuming soy protein or ISF.

High isoflavone soy diet increases insulin secretion without decreasing insulin sensitivity in premenopausal nonhuman primates

Consuming soy and soy isoflavones has been shown to cause modest improvements in plasma lipids, lipoproteins, and indices of insulin sensitivity in postmenopausal women. The effect of soy on such end points is attributed often to estrogen receptor agonism by isoflavones. Recent in vitro studies suggest that isoflavones, in combination with high estrogen concentrations (within the range seen circulating in premenopausal women), function as estrogen receptor antagonists that potentially may counteract the beneficial effects seen with soy consumption. We studied insulin sensitivity in 15 premenopausal nonhuman primates consuming either a high isoflavone soy diet or a soy-free casein/lactalbumin diet for 4 months. Insulin sensitivity was measured by intravenous glucose tolerance testing, hyperinsulinemic-euglycemic clamps, and insulin-stimulated insulin receptor and protein kinase B phosphorylation levels in muscle. In addition, plasma lipids, adiponectin, thyroid hormone, and body weights are reported. We show that high isoflavones do not adversely affect insulin sensitivity but do significantly alter insulin secretion to glucose stimulation. Small but significant increases in thyroxine and increased high-density lipoprotein cholesterol were observed as has been reported commonly with soy intake. These study results demonstrate that consumption of soy containing high isoflavone levels is not associated with changes in insulin sensitivity in the high estrogen milieu of the premenopausal female.

Genistein and daidzein induced apoA-1 transactivation in hepG2 cells expressing oestrogen receptor-α

Studies have shown that soya consumption has been associated with low incidence of CVD. Because the chemical structures of soya isoflavones are similar to oestrogen, the beneficial outcome may be attributed to the oestrogenicity of these compounds. In this study, effect of the soya isoflavone genistein on the mRNA expression of apoA-1 in the human hepatoma HepG2 cell was investigated. Without oestrogen receptor (ER) alpha transfection, soya isoflavones in the physiological range had no effect on the apoA-1 transcription. Once ERalpha was ectopically expressed in these cells, soya isoflavone dramatically increased the apoA-1 mRNA abundance quantified by real-time PCR. ApoA-1-reporter assays with plasmid constructed from the 5'-flanking segment upstream to the coding region revealed that the transactivation of the apoA-1 promoter was induced by the soya isoflavone in HepG2 cells expressing ERalpha. This induction was reduced by the anti-oestrogen ICI 182780, but not the inhibitors of protein kinase (PK) C, PKA, or mitogen-activated PK. Based on the previously identified response elements on the promoter, a series of truncated promoter reporter plasmids were then constructed. An induction profile of genistein was built and insulin response core element at -411 to -404 appeared to be a potential site of interaction. This study illustrated that soya isoflavones at physiological concentrations could up regulate apoA-1 mRNA expression in ERalpha-transfected HepG2 cells.

Soy consumption is not a risk factor for peanut sensitization

A recent cohort study suggested that intake of soy milk or soy formula was associated with peanut allergy. If this finding is confirmed, it suggests an avenue for modification of diet as a peanut allergy prevention strategy. To investigate the relationship between soy consumption and peanut sensitization in a prospective cohort study of children. A total of 620 babies with a family history of allergic disease were recruited. Dietary information was obtained from telephone interviews every 4 weeks from birth until 15 months and then again at 18 months and 2 years. Skin prick tests to peanut, milk, and egg were performed at 6, 12, and 24 months. A wheal size > or = 3 mm was considered positive for sensitization. Children whose parents elected to introduce soy formula or soy milk into their children's diet were more likely to be sensitized to peanuts at 2 years (odds ratio, 2.02; 95% CI, 1.04-3.92; P = .039). However, this relationship was explained by feeding of soy to children who had siblings with milk allergy or were themselves sensitized to milk. After adjusting for these factors, there was no evidence of an association between soy consumption and peanut sensitization (odds ratio, 1.34; 95% CI, 0.64-2.79; P = .434). The association between soy consumption and peanut sensitization is not causal but merely a result of preferential use of soy milk in infants with a personal or family history of cow's milk allergy. Future studies should take the confounding effects related to dietary modifications by parents into account when investigating the association between diet and childhood allergic diseases.

Soy consumption reduces the risk of non‐small‐cell lung cancers with epidermal growth factor receptor mutations among Japanese

Epidermal growth factor receptor (EGFR) mutations play substantial roles in genesis and proliferation of non-small-cell lung cancers (NSCLCs). We recently found that reproductive factors have a substantial impact on risk of development of NSCLCs featuring such EGFR mutations. Therefore, we explored the influence of dietary habits on NSCLC risk with reference to the EGFR mutational status. We conducted a case-control study using 353 patients with NSCLCs (122 EGFR mutated and 231 EGFR wild-type) and 1765 age-sex matched non-cancer control subjects. Dietary exposure was based on a semiquantitative food frequency questionnaire and impact of major food items, like meats, seafoods, vegetables and soybean products was assessed by multivariate logistic regression. Soybean products demonstrated a protective association with EGFR mutated, but not EGFR wild-type NSCLCs, with multivariate-adjusted odds ratios and 95% confidence intervals for the 2nd and 3rd tertile of soybean product consumption of 0.79 (0.50-1.27) and 0.56 (0.34-0.93) relative to those in the lowest tertile (trend P = 0.023). In conclusion, soy consumption may exert a protective association against the development of NSCLCs with EGFR mutations, providing possible insights into mechanisms of their genesis.

Soy intake is related to a lower body mass index in adult women

Experimental and epidemiologic studies suggest that soy may promote weight loss. The goal of this study was to examine the relation of soy intake with body weight over the lifespan of women with Caucasian, Japanese, and Native Hawaiian ancestry. We assessed the relation between lifetime soy consumption and body mass index (BMI) among 1,418 women in Hawaii. All subjects reported anthropometric measures, regular diet, and soy intake throughout life. The lifetime soy questionnaire was completed again by a subset of 356 women 5 years after study entry and the kappa values indicated moderate agreement. We regressed soy intake on BMI at study entry and at age 21 while controlling for confounding variables, computed least square means, and performed trend tests. Higher soy consumption in adulthood was related to a lower BMI (P=0.02). This association was only significant for Caucasian women and for postmenopausal subjects. The women in the highest category also experienced a smaller annual weight change since age 21 (by 0.05 kg/year) than the low soy intake group (P=0.02). We observed no association between early life soy intake and BMI. High vegetable consumption was significantly associated with a higher soy intake among Caucasian women. In this study, women consuming more soy during adulthood had a lower BMI, but the relation was primarily observed for Caucasian and postmenopausal subjects. This indicates that the association may be due to other nutritional factors and behaviors common in women with high soy intake.

Soy Consumption Is Associated With Peanut Sensitisation; Cause Or Confounding?

Soy Consumption Is Associated With Peanut Sensitisation; Cause Or Confounding?

Soybean snack does not inhibit post‐prandial fat oxidation

Soybean (Soy) intake after overnight fasting increased post‐prandial energy expenditure (EE) compared to wheat intake. We assessed the metabolic consequences of Soy or wheat snacks consumption. Ten healthy male volunteers (29.2 yrs, BMI= 23.7) attend 3 sessions (non‐snack: Non, Soy, Wheat) in a random order with at least one week of wash out period. Soy and Wheat trials were blinded. In each testing day, subjects ate regular breakfast at 0730 and lunch at 1200, and test snack (17 kJ/kg) at 1515 in Soy and Wheat sessions. Expired gas and blood samples were collected every an hour from 1100 until 2115 to determine EE and substrate oxidation (OX) and glucose, insulin and lipid profiles in the blood. Plasma glucose and serum insulin levels were markedly lower in Soy than in Wheat (P&lt;0.05). And those levels in Soy were only slightly higher compared to Non (P&lt;0.05). EE after snack was not different between three sessions. However, change in fat OX was higher and carbohydrate OX was lower in Soy and Non than in Wheat (P&lt;0.05). In addition, serum triglyceride level was higher in Soy than in Wheat and Non (P&lt;0.05). Serum free fatty acid level was higher in Non than in Soy, and further lower in Wheat (P&lt;0.05). These findings suggested that soybean snack does not inhibit acceleration of post‐prandial fat OX, but wheat snack does, possibly by insulin's action of fat storage.

Relationship between soy and isoflavone intake and periodontal disease: The Freshmen in Dietetic Courses Study II

BackgroundMuch research has shown that soy products inhibited various diseases. However, no published studies have examined the effects of consumption of soy and isoflavones on periodontal disease. The aim of this study was to investigate whether soy and isoflavone intake is associated with the prevalence of periodontal disease.MethodsThe subjects were 3956 Japanese female students, aged 18 to 22 years, who were taking a dietetic course. Periodontal disease was defined as present when a subject reported diagnosis of the disorder by a dentist. Information on dietary factors was collected using a validated diet history questionnaire. Logistic regression analysis was used to estimate the odds ratios and their confidence intervals of periodontal disease. Adjustment was made for cigarette smoking, toothbrushing frequency, region of residence, and body mass index.ResultsThe prevalence of periodontal disease was 8.0%. Intake of total soy product and tofu was independently associated with a decreased prevalence of periodontal disease; multivariate odds ratios in comparison of the highest with the lowest quintile were 0.68 and 0.68, respectively (95% confidence intervals = 0.47–0.97 and 0.47–0.98, P for trend = 0.01 and 0.004, respectively). A significant inverse dose-response relationship between the intake of isoflavones and the prevalence of periodontal disease was observed, although the difference in the adjusted odds ratio between the extreme quintiles was of borderline significance (P for trend = 0.04). There were no measurable dose-response relationships between consumption of tofu products, fermented soybeans, boiled soybeans, miso, or miso soup and the prevalence of periodontal disease.ConclusionOur findings suggest that soy and isoflavone intake may decrease the likelihood of periodontal disease. Further investigations with objective measures for periodontal disease are needed to confirm our findings.

Soy Protein Intake, Cardiorenal Indices, and C-Reactive Protein in Type 2 Diabetes With Nephropathy

Several short-term trials on the effect of soy consumption on cardiovascular risks are available, but little evidence exists regarding the impact of long-term soy protein consumption among type 2 diabetic patients with nephropathy. To determine the effects of long-term soy consumption on cardiovascular risks, we measured C-reactive protein (CRP) and kidney function indexes among type 2 diabetic patients with nephropathy. This longitudinal randomized clinical trial was conducted among 41 type 2 diabetic patients with nephropathy (18 men and 23 women). Twenty patients in the soy protein group consumed a diet containing 0.8 g protein/kg body weight (35% animal proteins, 35% textured soy protein, and 30% vegetable proteins) and 21 patients in the control group consumed a similar diet containing 70% animal proteins and 30% vegetable proteins for 4 years. Soy protein consumption significantly affected cardiovascular risks such as fasting plasma glucose (mean change in the soy protein versus control groups: -18 +/- 3 vs. 11 +/- 2 mg/dl; P = 0.03), total cholesterol (-23 +/- 5 vs. 10 +/- 3 mg/dl; P = 0.01), LDL cholesterol (-20 +/- 5 vs. 6 +/- 2 mg/dl; P = 0.01), and serum triglyceride (-24 +/- 6 vs. -5 +/- 2 mg/dl; P = 0.01) concentrations. Serum CRP levels were significantly decreased by soy protein intake compared with those in the control group (1.31 +/- 0.6 vs. 0.33 +/- 0.1 mg/l; P = 0.02). Significant improvements were also seen in proteinuria (-0.15 +/- 0.03 vs. 0.02 +/- 0.01 g/day; P = 0.001) and urinary creatinine (-1.5 +/- 0.9 vs. 0.6 +/- 0.3 mg/dl, P = 0.01) by consumption of soy protein. Longitudinal soy protein consumption significantly affected cardiovascular risk factors and kidney-related biomarkers among type 2 diabetic patients with nephropathy.

Consumption of fat-free fluid milk after resistance exercise promotes greater lean mass accretion than does consumption of soy or carbohydrate in young, novice, male weightlifters

Consumption of fat-free fluid milk after resistance exercise promotes greater lean mass accretion than does consumption of soy or carbohydrate in young, novice, male weightlifters