Effects of Soy Isoflavones on Biochemical Markers of Bone Metabolism in Postmenopausal Women: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Effects of isoflavone interventions on bone metabolism in perimenopausal and postmenopausal women: An umbrella review of meta-analyses of randomized controlled trials

OBJECTIVE

Previous meta-analyses have investigated the effects of isoflavones on bone metabolism in perimenopausal or postmenopausal women. However, there were still conflicting results. Thereby, this umbrella review assessed the existing meta-analysis evidence of the effects of isoflavone interventions on bone metabolism in perimenopausal and postmenopausal women.

METHODS

This study was conducted following the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). From the inception until August 24, 2023, PubMed, Embase, Cochrane, and Web of Science databases were searched to identify meta-analyses of randomized controlled trials (RCTs). The outcomes included bone mineral densities (BMDs), and bone turnover markers (BTMs) of osteocalcin (OC), bone-specific alkaline phosphatase (BAP), pyridinoline (PYD), deoxypyridinoline (DPD), Procollagen Type 1 N-Terminal Propeptide (P1NP), and C-telopeptide of Type 1 Collagen (CTX). The random-effects model was used to recalculate the extracted effect sizes. Mean difference (MD) was used as a summary effect measure.

RESULTS

Ten meta-analyses of RCTs were included. The isoflavone intervention was associated with increased BMDs in lumbar spine (MD: 11.50 mg/cm2, 95% confidence interval (CI): 6.46 to 16.55), femoral neck (MD: 2.03%, 95% CI: 0.57 to 3.50), and top hip (MD: 0.31%, 95% CI: 0.03 to 0.59) in perimenopausal and postmenopausal women.

CONCLUSION

Our findings indicate that isoflavone interventions have the potential to improve BMD at different bone sites, including the lumbar spine, femoral neck, and total hip in perimenopausal and postmenopausal women. Isoflavone may be considered a complementary option in the bone loss of perimenopausal and postmenopausal women.

Dietary Flavonoid and Subclass Intakes are not Associated with Markers of Bone Health in U.S. Adults Age 50+ Years

BACKGROUND

Dietary flavonoid intakes have been associated with improved markers of bone health in Chinese and Scottish cohorts, but little data exist in middle aged to older adults in the United States.

OBJECTIVES

The objective of our research was to assess if dietary flavonoid intakes are associated with bone mineral density (BMD), bone mineral content (BMC), and bone area of the lumbar spine and femoral neck in a nationally representative population of middle aged to older U.S. adults. We further sought to investigate if relationships of the main flavonoid subgroups (i.e., anthocyanins, flavan-3-ols, flavanones, flavones, flavonols, and isoflavones) exist, as a secondary objective.

METHODS

Cross-sectional data from individuals aged 50+ years enrolled in the 2017-2018 National Health and Nutrition Examination Survey (NHANES) were used in our analyses (N = 2590). Weighted multivariate logistic regression models were used to investigate the relationship between quartiles of flavonoid intake and BMD, BMC, and bone area of the lumbar spine and femoral neck of participants.

RESULTS

Mean age of participants was 63.4 ± 0.52 years and 64.1 ± 0.52 years for men and women, respectively. Average total flavonoid intake was 217 ± 19.4 mg/day and 306 ± 26.9 mg/day for men and women, respectively. Total flavonoid intakes were not significantly associated with BMD, BMC, or bone area of the femoral neck or lumbar spine in male or female participants. Flavonoid subclass intakes were also not consistently associated with improved markers of bone health.

CONCLUSION

Although several limitations exist, this cross-sectional analysis of U.S. adults aged 50+ years provides contradictory evidence to the hypothesis that higher flavonoid and flavonoid subclass intakes beneficially impacts markers of bone health. Large prospective cohort investigations that better capture long-term dietary flavonoid intake and ascertain fractures the primary outcome, as well as randomized controlled trials, are needed to fully elucidate the effects flavonoids on bone health.

Isoflavone intervention and its impact on bone mineral density in postmenopausal women: a systematic review and meta-analysis of randomized controlled trials

Due to estrogen deficiency, postmenopausal women may suffer from an imbalance in bone metabolism that leads to bone fractures. Isoflavones, a type of phytoestrogen, have been suggested to improve bone metabolism and increase bone mass. Therefore, isoflavones are increasingly recognized as a promising natural alternative to hormone replacement therapy for postmenopausal women who face a heightened risk of osteoporosis and are susceptible to bone fractures.

PURPOSE

This study aimed to evaluate the efficacy of isoflavone interventions on bone mineral density (BMD) in postmenopausal women by means of systematic review and meta-analysis.

METHODS

The electronic database searches were performed on PubMed, Embase, Scopus, and Cochrane Library databases, covering literature up to April 20, 2023. A random-effects model was used to obtain the main effect estimates, with a mean difference (MD) and its 95% confidence interval (CI) as the effect size summary. The risk of bias assessment was conducted using the Risk of Bias 2 (RoB2) tool.

RESULTS

A total of 63 randomized controlled trials comparing isoflavone interventions (n = 4,754) and placebo (n = 4,272) were included. The results indicated that isoflavone interventions significantly improved BMD at the lumbar spine (MD = 0.0175 g/cm2; 95% CI, 0.0088 to 0.0263, P < 0.0001), femoral neck (MD = 0.0172 g/cm2; 95% CI, 0.0046 to 0.0298, P = 0.0073), and distal radius (MD = 0.0138 g/cm2; 95% CI, 0.0077 to 0.0198, P < 0.0001) in postmenopausal women. Subgroup analysis showed that the isoflavone intervention was effective for improving BMD when the duration was ≥ 12 months and when the intervention contained genistein of at least 50 mg/day.

CONCLUSION

This systematic review and meta-analysis suggests that isoflavone interventions, especially those containing genistein of at least 50 mg/day, can effectively enhance BMD in postmenopausal women.

TC and LDL-C are negatively correlated with bone mineral density in patients with osteoporosis

OBJECTIVE

To investigate the relationships of multiple lipid metabolism indicators and bone turnover markers (BTMs) with bone mineral density (BMD) and osteoporosis, in order to identify high-risk populations.

METHODS

A total of 380 patients were recruited and their general information was collected. Linear and logistic regression models were used to analyze the correlation of these indicators with BMD and osteoporosis.

RESULTS

Lipid metabolism indices and BTMs exhibited varying degrees of positive or negative correlation with BMD. Elevated levels of triglycerides (r = -0.204, P = 0.004), total cholesterol (TC) (r = -0.244, P < 0.001), low-density lipoprotein cholesterol (LDL-C) (r = -0.256, P < 0.001), apoprotein B (r = -0.292, P < 0.001) and lipoprotein-associated phospholipase A2 (Lp-PLA2) (r = -0.221, P = 0.002) in women were associated with a reduction in BMD. This relationship persisted even after adjusting for confounding factors and in the subgroup analysis of elderly women. In males, TC (r = 0.159, P = 0.033), LDL-C (r = 0.187, P = 0.012), apoprotein B (r = 0.157, P = 0.035), and Lp-PLA2 (r = 0.168, P = 0.024) exhibited a positive correlation with BMD, while free fatty acid (FFA) (r = -0.153, P = 0.041) was negatively correlated with BMD. However, after adjusting for confounding factors, only FFA remained negatively correlated with BMD, which was not observed in the age subgroup analysis. Furthermore, elevated levels of TC and LDL-C in elderly women were positively associated with the risk of osteoporosis or low bone mass.

CONCLUSION

Elevated levels of TC and LDL-C not only indicate a decrease in BMD in females but also positively correlate with the occurrence of osteoporosis and low bone mass in elderly females.

Benefits of Soybean in the Era of Precision Medicine: A Review of Clinical Evidence

Soybean (Glycine max) is an important ingredient of cuisines worldwide. While there is a wealth of evidence that soybean could be a good source of macronutrients and phytochemicals with health-promoting effects, concerns regarding adverse effects have been raised. In this work, we reviewed the current clinical evidence focusing on the benefits and risks of soybean ingredients. In breast, prostate, colorectal, ovarian, and lung cancer, epidemiological studies showed an inverse association between soybean food intake and cancer risks. Soybean intake was inversely correlated with risks of type 2 diabetes mellitus (T2DM), and soy isoflavones ameliorated osteoporosis and hot flashes. Notably, soybean was one of the dietary protein sources that may reduce the risk of breast cancer and T2DM. However, soybean had adverse effects on certain types of drug treatment and caused allergies. In sum, this work provides useful considerations for planning clinical soybean research and selecting dietary protein sources for human health.

Effects of Isoflavonoid and Vitamin D Synergism on Bone Mineral Density-A Systematic and Critical Review

Phytoestrogens are non-steroidal plant compounds, which bind to α and β estrogen receptors, thereby causing specific effects. The best-known group of phytoestrogens are flavonoids, including isoflavonoids-genistein and daidzein. They play a role in the metabolism of bone tissue, improving its density and preventing bone loss, which contributes to reducing the risk of fractures. Vitamin D is found in the form of cholecalciferol (vitamin D3) and ergocalciferol (vitamin D2) and is traditionally recognized as a regulator of bone metabolism. The aim of this review was to evaluate the synergistic effect of isoflavonoids and vitamin D on bone mineral density (BMD). The MEDLINE (PubMed), Scopus and Cochrane databases were searched independently by two authors. The search strategy included controlled vocabulary and keywords. Reference publications did not provide consistent data regarding the synergistic effect of isoflavonoids on BMD. Some studies demonstrated a positive synergistic effect of these compounds, whereas in others, the authors did not observe any significant differences. Therefore, further research on the synergism of isoflavonoids and vitamin D may contribute to a significant progress in the prevention and treatment of osteoporosis.

The Effects of Polyphenols on Bone Metabolism in Postmenopausal Women: Systematic Review and Meta-Analysis of Randomized Control Trials

Osteoporosis is a condition favored by the postmenopausal decline in estrogen levels and worsened by oxidative stress (OS). Polyphenols are natural compounds abundantly found in fruits and vegetables, and they exert antioxidant and hormonal effects that could be useful in osteoporosis prevention, as suggested by epidemiological studies showing a lower incidence of fractures in individuals consuming polyphenol-rich diets. The aim of our meta-analysis is to evaluate the effects of polyphenols on bone mineral density (BMD, primary endpoint) and bone turnover markers (BTMs, secondary endpoint) in postmenopausal women. Twenty-one randomized control trials (RCTs) were included in our analysis after in-depth search on PubMed, EMBASE, and Scopus databases. We found that supplementation with polyphenols for 3-36 months exerted no statically significant effects on BMD measured at lumbar spine (sMD: 0.21, 95% CI [-0.08 to 0.51], p = 0.16), femoral neck (sMD: 0.16, 95% CI [-0.23 to 0.55], p = 0.42), total hip (sMD: 0.05, 95% CI [-0.14 to 0.24], p = 0.61), and whole body (sMD: -0.12, 95% CI [-0.42 to 0.17], p = 0.41). Subgroup analysis based on treatment duration showed no statistical significance, but a significant effect on lumbar BMD emerged when studies with duration of 24 months or greater were analyzed separately. On the other hand, we found a significantly slight increase in bone-specific alkaline phosphatase (BALP) levels (sMD: 1.27, 95% CI [1.13 to 1.42], p < 0.0001) and a decrease in pyridinoline (PD) levels (sMD: -0.58, 95% CI [-0.77 to -0.39], p < 0.0001). High heterogeneity among studies and unclear risk of bias in one third of the included studies emerged. A subgroup analysis showed similar effects for different duration of treatment and models of dual-energy X-ray absorptiometry (DXA) scanner. More robust evidence is needed before recommending the prescription of polyphenols in clinical practice.

Effects of isoflavone and probiotic intake on calcium transport and bone metabolism biomarkers in female rats

Calcium is essential for maintaining bone health as it contributes to bone formation, remodeling, strength, and density. This study investigated the effect of isoflavones and probiotics on calcium transporters' gene expression, serum calcium levels, and bone metabolism biomarkers in healthy female rats. Forty-eight female Wistar rats were classified into six groups. Bone metabolism biomarkers (pyridinoline, deoxypyridinoline, parathyroid hormone, and osteocalcin) and serum calcium levels were measured by enzyme-linked immunosorbent assay (ELISA) and atomic absorption spectroscopy (AAS), respectively. Gene expression of calcium transporters (Trpv5 and Trpv6) was evaluated in duodenum and jejunum tissue samples using quantitative polymerase chain reaction (qPCR). Trpv5 and Trpv6, epithelial calcium channels, play a crucial role in calcium transport and homeostasis in the body. The study consisted of a1-week adaptation period for the rats to adjust to the controlled conditions, followed by an 8-week intervention phase. The daidzein and genistein group showed a significant increase in the gene expression of the Trpv6 transporter in the duodenum and a marked decrease in serum pyridinoline levels compared to the control group. The tempeh and soybean groups showed a significant decrease in the gene expression of the Trpv5 calcium transporter in the jejunum. However, no significant influence of the Lactobacillus acidophilus diet on calcium transport and bone metabolism biomarkers was observed in the L. acidophilus group. The correlation analysis showed a significant positive relationship between serum calcium, bone metabolism biomarkers, and calcium transporters. In conclusion, our study demonstrates that the daidzein and genistein diet improves calcium transport in the duodenum and reduces pyridinoline serum concentrations, while tempeh and soybean diets reduce calcium transport in the jejunum. However, the combination of daidzein, genistein, and L. acidophilus did not demonstrate a synergistic effect on calcium transport and bone metabolism, suggesting that further investigations are needed to elucidate their potential interactions.

The Role of Choline, Soy Isoflavones, and Probiotics as Adjuvant Treatments in the Prevention and Management of NAFLD in Postmenopausal Women

Nonalcoholic fatty liver disease (NAFLD) is a prevalent condition among postmenopausal women that can lead to severe liver dysfunction and increased mortality. In recent years, research has focused on identifying potential lifestyle dietary interventions that may prevent or treat NAFLD in this population. Due to the complex and multifactorial nature of NAFLD in postmenopausal women, the disease can present as different subtypes, with varying levels of clinical presentation and variable treatment responses. By recognizing the significant heterogeneity of NAFLD in postmenopausal women, it may be possible to identify specific subsets of individuals who may benefit from targeted nutritional interventions. The purpose of this review was to examine the current evidence supporting the role of three specific nutritional factors-choline, soy isoflavones, and probiotics-as potential nutritional adjuvants in the prevention and treatment of NAFLD in postmenopausal women. There is promising evidence supporting the potential benefits of these nutritional factors for NAFLD prevention and treatment, particularly in postmenopausal women, and further research is warranted to confirm their effectiveness in alleviating hepatic steatosis in this population.

Equol exerts a protective effect on postmenopausal osteoporosis by upregulating OPG/RANKL pathway

BACKGROUD

Estrogen deficiency is the leading cause of postmenopausal osteoporosis(PMOP) and phytoestrogens soy isoflavones (SI) have been shown to improve PMOP. Equol (Eq), an in vivo metabolite of phytoestrogens soy isoflavones (SI), has a more stable structure and stronger biological activity than its parent compound and has the greatest estrogenic activity. However, there are few studies on the therapeutic effect of Eq on PMOP.

PURPOSE

To explore the therapeutic effect and mechanisms of Eq on POMP.

METHODS

Osteoblast-like cells ROS1728 were cultured with different doses of Eq, estradiol (E2), separately. The effect of Eq on the proliferation, apoptosis, cell cycle of osteoblasts were detected by CCK-8 and flow cytometry, and the expression of OPG/RANK/RANKL signaling pathway of osteoblasts was detected by Quantitative real-time PCR (qRT-PCR) and Western blot (WB), and RNA silencing technology were carried out to explore the receptors through which Eq plays a role. Then PMOP rat model was established and treated by Eq or E2 to further verification of the effect and mechanism of Eq on PMOP.

RESULT

Eq promoted the proliferation and inhibited the apoptosis of osteoblasts and increased the proportion of osteoblasts in the S phase and G2/M phase in a dose-dependent manner. Mechanistically, Eq treatment upregulated the expression of OPG and OPG/RANKL ratio in osteoblasts and this regulatory effect was mainly mediated through the ERβ receptor. Furthermore, in vivo study, Eq improved microstructure and BMD of the femur of PMOP rat model, which imitated the osteoprotective effect of E2. Moreover, the Eq or E2 treatment increased serum levels of Ca, 1,25(OH)2D3, bone Gla-protein(BGP), and Type I procollagen (PC1), and reduced serum levels of phosphorus (P), parathyroid hormone(PTH), pyridinol (PYD), tartrate-resistant acid phosphatase (TRAP) and urinary level of deoxypyridinoline (DPD) in the treatment OVX group compared with the untreated OVX group. Meanwhile, Eq or E2 markedly induced the mRNA and protein expression of OPG and OPG/RANKL ratio.

CONCLUSION

Eq can combine with ERβ and exert a protective effect on PMOP by upregulating OPG/RANKL pathway.

Sustainability and Gender Perspective in Food Innovation: Foods and Food Processing Coproducts as Source of Macro- and Micro-Nutrients for Woman-Fortified Foods

Micro- and macro-nutrient deficiencies among women are considered a global issue that the food industry has not adequately considered until recently. The industry must provide and guarantee a diversity of food products worldwide that allow women to get a correct and balanced diet according their life stage. The food industry must focus on this challenge within a framework of sustainable production, minimizing the use of natural resources and avoiding the emission of waste and pollutants throughout the life cycle of food. Food coproducts are presented as potential bioactive functional compounds which can be useful for technological purposes, due to the fact that they can serve as non-chemical, natural and health-improving food ingredients. In this review, we focus on the potential use of food processing coproducts which must be part of a strategy to promote and improve women's health and well-being. This knowledge will make it possible to select potential ingredients from coproducts to be used in the fortification of foods intended for consumption by females and to introduce sustainability and gender perspectives into food innovation. The attainment of fortifications for foods for women has to be linked to the use of sustainable sources from food coproducts in order to be economically viable and competitive.

Soy Isoflavones and Bone Health: Focus on the RANKL/RANK/OPG Pathway

Bone remodels via resorption and formation, two phenomena that continuously occur in bone turnover. The RANKL/RANK/OPG pathway is one of the several mechanisms that affect bone turnover. The RANKL/OPG ratio has a substantial role in bone resorption. An imbalance between formation and resorption is related to an increased RANKL/OPG balance. OPG, a member of this system, can bind to RANKL and suppress RANK-RANKL interaction, and subsequently, inhibit further osteoclastogenesis. The serum levels of RANKL and OPG in the bone microenvironment are vital for osteoclasts formation. The RANK/RANKL/OPG system plays a role in the pathogenesis of bone disorders. This system can be considered a new treatment target for bone disorders. Soy isoflavones affect the RANK/RANKL/OPG system through numerous mechanisms. Soy isoflavones decrease RANKL levels and increase OPG levels. Therefore, isoflavones improve bone metabolism and decrease bone resorption. Soy isoflavones decrease serum markers of bone resorption and improve bone metabolism. However, while the available data are promising, the results of several studies reported no change in RANKL and OPG levels with isoflavones supplementation. In this regard, current evidence is insufficient for conclusive approval of the efficacy of isoflavones on RANKL/RANK/OPG and further research, including animal and human studies, are needed to confirm the effect of soy isoflavones on the RANKL/RANK/OPG pathway. This study was a review of available evidence to determine the role of isoflavones in bone hemostasis and the RANK/RANKL/OPG pathway. The identification of the effects of isoflavones on the RANKL/RANK/OPG pathway directs future studies and leads to the development of effective treatment strategies for bone disorders.

The health effects of soy: A reference guide for health professionals

Soy is a hotly debated and widely discussed topic in the field of nutrition. However, health practitioners may be ill-equipped to counsel clients and patients about the use of soyfoods because of the enormous, and often contradictory, amount of research that has been published over the past 30 years. As interest in plant-based diets increases, there will be increased pressure for practitioners to gain a working knowledge of this area. The purpose of this review is to provide concise literature summaries (400-500 words) along with a short perspective on the current state of knowledge of a wide range of topics related to soy, from the cholesterol-lowering effects of soy protein to the impact of isoflavones on breast cancer risk. In addition to the literature summaries, general background information on soyfoods, soy protein, and isoflavones is provided. This analysis can serve as a tool for health professionals to be used when discussing soyfoods with their clients and patients.

Current Perspectives on the Beneficial Effects of Soybean Isoflavones and Their Metabolites for Humans

Soybeans are rich in proteins and lipids and have become a staple part of the human diet. Besides their nutritional excellence, they have also been shown to contain various functional components, including isoflavones, and have consequently received increasing attention as a functional food item. Isoflavones are structurally similar to 17-β-estradiol and bind to estrogen receptors (ERα and ERβ). The estrogenic activity of isoflavones ranges from a hundredth to a thousandth of that of estrogen itself. Isoflavones play a role in regulating the effects of estrogen in the human body, depending on the situation. Thus, when estrogen is insufficient, isoflavones perform the functions of estrogen, and when estrogen is excessive, isoflavones block the estrogen receptors to which estrogen binds, thus acting as an estrogen antagonist. In particular, estrogen antagonistic activity is important in the breast, endometrium, and prostate, and such antagonistic activity suppresses cancer occurrence. Genistein, an isoflavone, has cancer-suppressing effects on estrogen receptor-positive (ER+) cancers, including breast cancer. It suppresses the function of enzymes such as tyrosine protein kinase, mitogen-activated kinase, and DNA polymerase II, thus inhibiting cell proliferation and inducing apoptosis. Genistein is the most biologically active and potent isoflavone candidate for cancer prevention. Furthermore, among the various physiological functions of isoflavones, they are best known for their antioxidant activities. S-Equol, a metabolite of genistein and daidzein, has strong antioxidative effects; however, the ability to metabolize daidzein into S-equol varies based on racial and individual differences. The antioxidant activity of isoflavones may be effective in preventing dementia by inhibiting the phosphorylation of Alzheimer's-related tau proteins. Genistein also reduces allergic responses by limiting the expression of mast cell IgE receptors, which are involved in allergic responses. In addition, they have been known to prevent and treat various diseases, including cardiovascular diseases, metabolic syndromes, osteoporosis, diabetes, brain-related diseases, high blood pressure, hyperlipidemia, obesity, and inflammation. Further, it also has positive effects on menstrual irregularity in non-menopausal women and relieving menopausal symptoms in middle-aged women. Recently, soybean consumption has shown steep increasing trend in Western countries where the intake was previously only 1/20-1/50 of that in Asian countries. In this review, I have dealt with the latest research trends that have shown substantial interest in the biological efficacy of isoflavones in humans and plants, and their related mechanisms.