Soy isoflavones consumption and risk of breast cancer incidence or recurrence: a meta-analysis of prospective studies

Soy-Based Therapeutic Baby Formulas: Testable Hypotheses Regarding the Pros and Cons

Soy-based infant formulas have been consumed in the United States since 1909, and currently constitute a significant portion of the infant formula market. There are efforts underway to generate genetically modified soybeans that produce therapeutic agents of interest with the intent to deliver those agents in a soy-based infant formula platform. The threefold purpose of this review article is to first discuss the pros and cons of soy-based infant formulas, then present testable hypotheses to discern the suitability of a soy platform for drug delivery in babies, and finally start a discussion to inform public policy on this important area of infant nutrition.

Botanicals and Their Bioactive Phytochemicals for Women's Health

Botanical dietary supplements are increasingly popular for women's health, particularly for older women. The specific botanicals women take vary as a function of age. Younger women will use botanicals for urinary tract infections, especially Vaccinium macrocarpon (cranberry), where there is evidence for efficacy. Botanical dietary supplements for premenstrual syndrome (PMS) are less commonly used, and rigorous clinical trials have not been done. Some examples include Vitex agnus-castus (chasteberry), Angelica sinensis (dong quai), Viburnum opulus/prunifolium (cramp bark and black haw), and Zingiber officinale (ginger). Pregnant women have also used ginger for relief from nausea. Natural galactagogues for lactating women include Trigonella foenum-graecum (fenugreek) and Silybum marianum (milk thistle); however, rigorous safety and efficacy studies are lacking. Older women suffering menopausal symptoms are increasingly likely to use botanicals, especially since the Women's Health Initiative showed an increased risk for breast cancer associated with traditional hormone therapy. Serotonergic mechanisms similar to antidepressants have been proposed for Actaea/Cimicifuga racemosa (black cohosh) and Valeriana officinalis (valerian). Plant extracts with estrogenic activities for menopausal symptom relief include Glycine max (soy), Trifolium pratense (red clover), Pueraria lobata (kudzu), Humulus lupulus (hops), Glycyrrhiza species (licorice), Rheum rhaponticum (rhubarb), Vitex agnus-castus (chasteberry), Linum usitatissimum (flaxseed), Epimedium species (herba Epimedii, horny goat weed), and Medicago sativa (alfalfa). Some of the estrogenic botanicals have also been shown to have protective effects against osteoporosis. Several of these botanicals could have additional breast cancer preventive effects linked to hormonal, chemical, inflammatory, and/or epigenetic pathways. Finally, although botanicals are perceived as natural safe remedies, it is important for women and their healthcare providers to realize that they have not been rigorously tested for potential toxic effects and/or drug/botanical interactions. Understanding the mechanism of action of these supplements used for women's health will ultimately lead to standardized botanical products with higher efficacy, safety, and chemopreventive properties.

Effects of High-Order Interactions among IGFBP-3 Genetic Polymorphisms, Body Mass Index and Soy Isoflavone Intake on Breast Cancer Susceptibility

Background

Polymorphisms of IGF-1 and IGFBP-3 and environmental factors may work together to influence insulin-like growth factor (IGF) levels and thus breast cancer (BC) risk. However, very few studies have investigated high-order interactions among these variables.

Methods

A total of 277 newly diagnosed BC cases and 277 controls were recruited between October 2010 and July 2012. We collected each participant's demographic characteristics, dietary intake, and blood sample. IGF-1 rs1520220 and IGFBP-3 rs2854744 were then genotyped. A multi-analytic strategy combining unconditional logistic regression (ULR), generalized multifactor dimensionality reduction (GMDR), and classification and regression tree (CART) approaches was applied to systematically identify the interactions of the two single nucleotide polymorphisms (SNPs), body mass index (BMI), and daily intake of soy isoflavone (DISI) on BC susceptibility.

Results

In GMDR analyses, high-order interactions among BMI, DISI, and SNP rs2854744 were identified among overall and postmenopausal women. We also found significant dosage effects on BC risk with an increasing number of exposure factors, namely carrying the rs2854744 AA genotype, DISI <9.85 mg/day, and BMI ≥24 kg/m² (P_trend<0.05). Similarly, in CART analyses, compared with individuals having BMI<24kg/m², DISI<9.85 mg/day, and the rs2854744 CC+CA genotype, BC risk increased significantly for those carrying the rs2854744 AA genotype, with BMI<24 kg/m² and DISI<9.85 mg/day (OR = 1.95, 95%CI: 1.03–3.69), and also for those with BMI≥24kg/m² and DISI<9.85 mg/day (OR = 2.13, 95%CI: 1.00–4.51). Similar interaction effects were observed among postmenopausal women.

Conclusions

This study suggests high-order interactions of the IGFBP-3 rs2854744 AA genotype, BMI≥24kg/m², and DISI<9.85 mg/day on increased BC risk, particularly among postmenopausal women.

Oral Administration of Fermented Soymilk Products Protects the Skin of Hairless Mice against Ultraviolet Damage

The protective effect of isoflavones on skin damage from ultraviolet (UV) radiation and their bioavailability were investigated in ovariectomized hairless mice fed diets composed of fermented soymilk containing aglycone forms of isoflavones or control soymilk containing glucose-conjugated forms of isoflavones. The erythema intensity of dorsal skin was significantly higher in ovariectomized mice than in sham-operated mice (p < 0.05). The erythema intensity and epidermal thickness of dorsal skin were significantly lower in the fermented soymilk diet group than in the control diet group (each p < 0.05). Levels of cyclobutane pyrimidine dimers in dorsal skin were significantly lower in the fermented soymilk diet group than in the control group (p < 0.05). Serum and dorsal skin isoflavone concentrations were significantly higher in the fermented soymilk diet group than in the soymilk diet group (p < 0.05). These results indicate that oral administration of a fermented soymilk diet increases isoflavone concentrations in the blood and skin, effectively scavenging the reactive oxygen species generated by UV irradiation and exerting an estrogen-like activity, with a consequent protective effect on skin photodamage in hairless mice.

Effects of soy containing diet and isoflavones on cytochrome P450 enzyme expression and activity

Cytochromes P450 (CYPs) play an important role in metabolism and clearance of most clinically utilized drugs and other xenobiotics. They are important in metabolism of endogenous compounds including fatty acids, sterols, steroids and lipid-soluble vitamins. Dietary factors such as phytochemicals are capable of affecting CYP expression and activity, which may be important in diet-drug interactions and in the development of fatty liver disease, cardiovascular disease and cancer. One important diet-CYP interaction is with diets containing plant proteins, particularly soy protein. Soy diets are traditionally consumed in Asian countries and are linked to lower incidence of several cancers and of cardiovascular disease in Asian populations. Soy is also an important protein source in vegetarian and vegan diets and the sole protein source in soy infant formulas. Recent studies suggest that consumption of soy can inhibit induction of CY1 enzymes by polycyclic aromatic hydrocarbons (PAHs) which may contribute to cancer prevention. In addition, there are data to suggest that soy components promiscuously activate several nuclear receptors including PXR, PPAR and LXR resulting in increased expression of CYP3As, CYP4As and CYPs involved in metabolism of cholesterol to bile acids. Such soy-CYP interactions may alter drug pharmacokinetics and therapeutic efficacy and are associated with improved lipid homeostasis and reduced risk of cardiovascular disease. The current review summarizes results from in vitro; in vivo and clinical studies of soy-CYP interactions and examines the evidence linking the effects of soy diets on CYP expression to isoflavone phytoestrogens, particularly, genistein and daidzein that are associated with soy protein.

The association of soy food consumption with the risk of subtype of breast cancers defined by hormone receptor and HER2 status

Soy food intake has previously been associated with reduced breast cancer risk. Epidemiological evidence for subgroups of breast cancer, particularly by menopausal and hormone receptor status, is less consistent. To evaluate the role of hormone receptor and menopausal status on the association between soy food intake and breast cancer risk, we measured usual soy food intake in adolescence and adulthood via food frequency questionnaire in 70,578 Chinese women, aged 40-70 years, recruited to the Shanghai Women's Health Study (1996-2000). After a median follow-up of 13.2 years (range: 0.01-15.0), 1,034 incident breast cancer cases were identified. Using Cox models, we found that adult soy intake was inversely associated with breast cancer risk [hazard ratio (HR) for fifth versus first quintile soy protein intake = 0.78; 95% confidence interval (CI):0.63-0.97]. The association was predominantly seen in premenopausal women (HR = 0.46; 95% CI:0.29-0.74). Analyses further stratified by hormone receptor status showed that adult soy intake was associated with significantly decreased risk of estrogen receptor (ER)+/progesterone receptor (PR)+ breast cancer in postmenopausal women (HR = 0.72; 95% CI:0.53-0.96) and decreased risk of ER-/PR- breast cancer in premenopausal women (HR = 0.46; 95% CI:0.22-0.97). The soy association did not vary by human epidermal growth factor-2 (HER2) status. Furthermore, we found that high soy intake during adulthood and adolescence was associated with reduced premenopausal breast cancer risk (HR = 0.53; 95% CI: 0.32-0.88; comparing third vs. first tertile) while high adulthood soy intake was associated with postmenopausal breast cancer only when adolescent intake was low (HR = 0.63; 95% CI: 0.43-0.91). Our study suggests that hormonal status, menopausal status and time window of exposure are important factors influencing the soy-breast cancer association.

Glycone-rich Soy Isoflavone Extracts Promote Estrogen Receptor Positive Breast Cancer Cell Growth

Due to the association of hormone replacement therapy (HRT) with breast cancer risk, estrogenically active soy isoflavones are considered as an HRT alternative to alleviate menopausal symptoms. However, several recent reports challenged the health benefits of soy isoflavones and associated them with breast cancer promotion. While glyconic isoflavones are the major constituents of soybean seeds, due to their low cell permeability, they are considered to be biologically inactive. The glyconic isoflavones may exert their effects on membrane-bound estrogen receptors or could be converted to aglycones by extracellular β-glucosidases. Therefore, we hypothesized that despite their low cell permeability, soybean cultivars with high glyconic isoflavones may promote breast cancer cell growth. To test this, composition and estrogenic activity of isoflavones from 54 commercial soybean cultivars were determined. Soybean seeds produced in identical climate and growth conditions were used to minimize the effects of extraneous factors on isoflavone profile and concentrations. The glyconic daidzin concentration negatively correlated with genistin and with other aglycones. Relative to control, isoflavone extracts from 51 cultivars were estrogenic and promoted the growth of estrogen receptor positive (ER+) breast cancer cell line MCF-7 from 1.14 to 4.59 folds and other three cultivars slightly reduced the growth. Among these, extracts from three cultivars were highly estrogenic and promoted MCF-7 cell growth by 2.59-4.64 folds (P<0.005). Among six isoflavones, daidzin was positively associated with MCF-7 cell growth (P<0.005, r = 0.13966), whereas the negative correlation between genistin and MCF-7 cell growth was nearly significant (P≤0.0562, r = -0.026141). Furthermore, in drug interaction studies daidzin-rich isoflavone extracts antagonized tamoxifen, an ER inhibitor. Taken together, our results suggest that the glyconic daidzin-rich soy isoflavone extracts may exert estrogenic effects and promote ER+ breast cancer growth.

Diet and risk of breast cancer

Diet may play a role in both promoting and inhibiting human breast cancer development. In this review, nutritional risk factors such as consumption of dietary fat, meat, fiber, and alcohol, and intake of phytoestrogen, vitamin D, iron, and folate associated with breast cancer are reviewed. These nutritional factors have a variety of associations with breast cancer risk. Type of fat consumed has different effects on risk of breast cancer: consumption of meat is associated with heterocyclic amine (HCA) exposure; different types of plant fiber have various effects on breast cancer risk; alcohol consumption may increase the risk of breast cancer by producing acetaldehyde and reactive oxygen species (ROS); intake of phytoestrogen may reduce risk of breast cancer through genomic and non-genomic action; vitamin D can reduce the risk of breast cancer by inhibiting the process of cancer invasion and metastasis; intake of dietary iron may lead to oxidative stress, DNA damage, and lipid peroxidation; and lower intake of folate may be linked to a higher risk of breast cancer.

Breast cancer survival among young women: a review of the role of modifiable lifestyle factors

Almost 7 % of breast cancers are diagnosed among women age 40 years and younger in Western populations. Clinical outcomes among young women are worse. Early age-of-onset increases the risk of contralateral breast cancer, local and distant recurrence, and subsequent mortality. Breast cancers in young women (BCYW) are more likely to present with triple-negative (TNBC), TP53-positive, and HER-2 over-expressing tumors than among older women. However, despite these known differences in breast cancer outcomes and tumor subtypes, there is limited understanding of the basic biology, epidemiology, and optimal therapeutic strategies for BCYW. Several modifiable lifestyle factors associated with reduced risk of developing breast cancer have also been implicated in improved prognosis among breast cancer survivors of all ages. Given the treatment-related toxicities and the extended window for late effects, long-term lifestyle modifications potentially offer significant benefits to BCYW. In this review, we propose a model identifying three main areas of lifestyle factors (energy imbalance, inflammation, and dietary nutrient adequacy) that may influence survival in BCYW. In addition, we provide a summary of mechanisms of action and a synthesis of previous research on each of these topics.

Can diet and lifestyle prevent breast cancer: what is the evidence?

Breast cancer is the most common cancer among women in both developed and less-developed countries. Rates of breast cancer are increasing worldwide, with a particular increase in postmenopausal and estrogen receptor-positive cases. The World Cancer Research Fund (WCRF) and American Cancer Society (ACS) cancer prevention guidelines recommend maintaining a healthy weight, undertaking at least 150 minutes of moderate intensity exercise per week, limiting alcohol consumption, and eating a plant-based diet. Observational data link adherence to physical activity and alcohol guidelines throughout life to a reduced risk of developing pre- and postmenopausal breast cancer. Weight control throughout life appears to prevent cases after menopause. Adherence to a healthy dietary pattern does not have specific effects on breast cancer risk but remains important as it reduces the risk for other common diseases, such as cardiovascular disease (CVD), diabetes, and dementia. Emerging data suggest that smoking during adolescence or early adulthood increases later risk of breast cancer. Lifestyle factors appear to modify risk among high-risk women with a family history and those with typical risk of the general population, although their effects among carriers of BRCA mutations are not well defined. Recent expert reports estimate that successful lifestyle changes could prevent 25% to 30% of cases of breast cancer. These reductions will only be achieved if we can implement targeted prevention programs for high-risk women and women in population-based breast screening programs during childhood, adolescence, and early adulthood when the rapidly developing breast is particularly susceptible to carcinogenesis.

Profiling of Phenolic Metabolites in Feces from Menopausal Women after Long-Term Isoflavone Supplementation

Phenolic compounds were screened by UPLC-ESI-MS/MS in the feces of 15 menopausal women before and after long-term isoflavone treatment. In total, 44 compounds were detected. Large intertreatment, interindividual, and intersample variations were observed in terms of the number of compounds and their concentration. Four compounds, the aglycones daidzein and genistein and the daidzein derivatives dihydrodaidzein and O-desmethylangolensin, were associated with isoflavone metabolism; these were identified only after the isoflavone treatment. In addition, 4-ethylcatechol, 3-hydroxyphenylacetic acid, and 3-phenylpropionic acid differed significantly in pre- and postintervention samples, whereas the concentration of 4-hydroxy-5-phenylvaleric acid showed a trend toward increasing over the treatment. The phenolic profiles of equol-producing and -non-producing groups were similar, with the exceptions of 3-hydroxyphenylacetic acid and 3-phenylpropionic acid, which showed higher concentrations in equol-non-producing women. These findings may help to trace isoflavone-derived metabolites in feces during isoflavone interventions and to design new studies to address their biological effects.

Dairy consumption and lung cancer risk: a meta-analysis of prospective cohort studies

Background

Lung cancer risk is the leading cause of cancer-related deaths worldwide. We conducted a meta-analysis to evaluate the relationship between dairy consumption and lung cancer risk.

Methods

The databases included EMBASE, Medline (PubMed), and Web of Science. The relationship between dairy consumption and lung cancer risk was analyzed by relative risk or odds ratio estimates with 95% confidence intervals (CIs). We identified eight prospective cohort studies, which amounted to 10,344 cases and 61,901 participants.

Results

For milk intake, relative risk was 0.95 (95% CI: 0.76–1.15); heterogeneity was 70.2% (P=0.003). For total dairy product intake, relative risk was 0.96 (95% CI: 0.89–1.03), heterogeneity was 68.4% (P=0.004).

Conclusion

There was no significant association between dairy consumption and lung cancer risk.

Soy Isoflavones and Breast Cancer Cell Lines: Molecular Mechanisms and Future Perspectives

The potential benefit of soy isoflavones in breast cancer chemoprevention, as suggested by epidemiological studies, has aroused the interest of numerous scientists for over twenty years. Although intensive work has been done in this field, the preclinical results continue to be controversial and the molecular mechanisms are far from being fully understood. The antiproliferative effect of soy isoflavones has been commonly linked to the estrogen receptor interaction, but there is growing evidence that other pathways are influenced as well. Among these, the regulation of apoptosis, cell proliferation and survival, inhibition of angiogenesis and metastasis or antioxidant properties have been recently explored using various isoflavone doses and various breast cancer cells. In this review, we offer a comprehensive perspective on the molecular mechanisms of isoflavones observed in in vitro studies, emphasizing each time the dose-effect relationship and estrogen receptor status of the cells. Furthermore, we present future research directions in this field which could provide a better understanding of the inner molecular mechanisms of soy isoflavones in breast cancer.

Double-Blind Randomized 12-Month Soy Intervention Had No Effects on Breast MRI Fibroglandular Tissue Density or Mammographic Density

Soy supplementation by patients with breast cancer remains controversial. No controlled intervention studies have investigated the effects of soy supplementation on mammographic density in patients with breast cancer. We conducted a double-blind, randomized, placebo-controlled intervention study in previously treated patients with breast cancer (n = 66) and high-risk women (n = 29). We obtained digital mammograms and breast MRI scans at baseline and after 12 months of daily soy (50 mg isoflavones per day; n = 46) or placebo (n = 49) tablet supplementation. The total breast area (MA) and the area of mammographic density (MD) on the mammogram were measured using a validated computer-assisted method, and mammographic density percent (MD% = 100 × MD/MA) was determined. A well-tested computer algorithm was used to quantitatively measure the total breast volume (TBV) and fibroglandular tissue volume (FGV) on the breast MRI, and the FGV percent (FGV% = 100 × FGV/TBV) was calculated. On the basis of plasma soy isoflavone levels, compliance was excellent. Small decreases in MD% measured by the ratios of month 12 to baseline levels were seen in the soy (0.95) and the placebo (0.87) groups; these changes did not differ between the treatments (P = 0.38). Small decreases in FGV% were also found in both the soy (0.90) and the placebo (0.92) groups; these changes also did not differ between the treatments (P = 0.48). Results were comparable in patients with breast cancer and high-risk women. We found no evidence that soy supplementation would decrease mammographic density and that MRI might be more sensitive to changes in density than mammography.

Lifestyle, nutrition and breast cancer: facts and presumptions for consideration

Breast cancer is the most common cancer in women worldwide, and the high incidence of this cancer coupled with improvements in initial treatments has led to an ever-increasing number of breast cancer survivors. Among the prospective epidemiological studies on diet and breast cancer incidence and recurrence, to date, there is no association that is strong, reproducible and statistically significant, with the exception of alcohol intake, overweight, and weight gain. Nevertheless, many beliefs about food and breast cancer persist in the absence of supporting scientific evidence.

After a comprehensive review regarding the role of lifestyle on breast cancer outcomes and a thorough study of the dissemination field including mass media, clinical institutions, and academic figures, we briefly reported the most common presumptions and also facts from the literature regarding lifestyle, nutrition, and breast cancer.

The randomised controlled trial is the best study-design that could provide direct evidence of a causal relationship; however, there are methodological difficulties in applying and maintaining a lifestyle intervention for a sufficient period; consequently, there is a lack of this type of study in the literature. Instead, it is possible to obtain indirect evidence from observational prospective studies. In this article, it becomes clear that for now the best advice for women’s health is to follow the World Cancer Research Fund/American Institute of Cancer Research (WCRF/AICR) recommendations on diet, nutrition, physical activity, and weight management for cancer prevention, because they are associated with a lower risk of developing most types of cancer, including breast cancer. Despite current awareness of the role of nutrition in cancer outcomes, there is inadequate translation from research findings into clinical practice. We suggest the establishment of a multidisciplinary research consortium to demonstrate the real power of lifestyle interventions.

Epigenetic activities of flavonoids in the prevention and treatment of cancer

Aberrant epigenetic modifications are described in an increasing number of pathological conditions, including neurodegenerative diseases, cardiovascular diseases, diabetes mellitus type 2, obesity and cancer. The general reversibility of epigenetic changes makes them an attractive and promising target e.g. in the treatment of cancer. Thus, a growing number of epigenetically active compounds are currently tested in clinical trials for their therapeutic potential. Interestingly, many phytochemicals present in plant foods, particularly flavonoids, are suggested to be able to alter epigenetic cellular mechanisms. Flavonoids are natural phenol compounds that form a large group of secondary plant metabolites with interesting biological activities. They can be categorized into six major subclasses, which display diverse properties affecting the two best characterized epigenetic mechanisms: modulation of the DNA methylation status and histone acetylation. High dietary flavonoid intake has strongly been suggested to reduce the risk of numerous cancer entities in a large body of epidemiological studies. Established health-promoting effects of diets rich in fruit and vegetables are faced by efforts to use purified flavonoids as supplements or pharmaceuticals, whereupon data on the latter applications remain controversial. The purpose of this review is to give an overview of current research on flavonoids to further elucidate their potential in cancer prevention and therapy, thereby focusing on their distinct epigenetic activities.

Genistein and cancer: current status, challenges, and future directions

Primary prevention through lifestyle interventions is a cost-effective alternative for preventing a large burden of chronic and degenerative diseases, including cancer, which is one of the leading causes of morbidity and mortality worldwide. In the past decade, epidemiologic and preclinical evidence suggested that polyphenolic phytochemicals present in many plant foods possess chemopreventive properties against several cancer forms. Thus, there has been increasing interest in the potential cancer chemopreventive agents obtained from natural sources, such as polyphenols, that may represent a new, affordable approach to curb the increasing burden of cancer throughout the world. Several epidemiologic studies showed a relation between a soy-rich diet and cancer prevention, which was attributed to the presence of a phenolic compound, genistein, present in soy-based foods. Genistein acts as a chemotherapeutic agent against different types of cancer, mainly by altering apoptosis, the cell cycle, and angiogenesis and inhibiting metastasis. Targeting caspases, B cell lymphoma 2 (Bcl-2)-associated X protein (Bax), Bcl-2, kinesin-like protein 20A (KIF20A), extracellular signal-regulated kinase 1/2 (ERK1/2), nuclear transcription factor κB (NF-κB), mitogen-activated protein kinase (MAPK), inhibitor of NF-κB (IκB), Wingless and integration 1 β-catenin (Wnt/β-catenin), and phosphoinositide 3 kinase/Akt (PI3K/Akt) signaling pathways may act as the molecular mechanisms of the anticancer, therapeutic effects of genistein. Genistein also shows synergistic behavior with well-known anticancer drugs, such as adriamycin, docetaxel, and tamoxifen, suggesting a potential role in combination therapy. This review critically analyzes the available literature on the therapeutic role of genistein on different types of cancer, focusing on its chemical features, plant food sources, bioavailability, and safety.

Diet and cancer risk in the Korean population: a meta- analysis

Many studies have found links between diet and cancer. The summary estimates of the association between dietary factors and cancer risk were investigated using previously reported studies of the Korean population. Gastric cancer risk was inversely associated with the high intake of soy foods [OR (95% CI): 0.32 (0.25-0.40) for soybean, 0.56 (0.45-0.71) for soybean curd, and 0.67 (0.46-0.98) for soymilk], allium vegetables [OR (95% CI): 0.37 (0.26-0.53) for green onion, 0.54 (0.40-0.73) for garlic, and 0.54 (0.35-0.85) for onion], fruits [OR (95% CI): 0.61 (0.42-0.88)], and mushrooms [OR (95% CI): 0.43 (0.21-0.88)]. Salt and Kimchi were associated with an increased gastric cancer risk [OR (95% CI): 1.92 (1.52-2.43) and 2.21 (1.29-3.77), respectively]. Colorectal cancer risk was positively associated with meat intake [OR (95% CI): 1.25 (1.15-1.36)]. Total soy products, soybean curd, and soymilk showed an inverse association with breast cancer risk [OR (95% CI): 0.61 (0.38-0.99), 0.47 (0.34-0.66), and 0.75 (0.57-0.98), respectively]. Green/yellow and light colored vegetables were associated with a reduced risk of breast cancer [OR (95% CI): 0.34 (0.23-0.49) and 0.44 (0.21-0.90), respectively]. Mushroom intake was inversely associated in pre-menopausal women only [OR (95% CI): 0.47 (0.26-0.86)]. In conclusion, soy foods, fruits and vegetables might reduce cancer risk in the Korean population. High salt food might be risk factor for gastric cancer, and intake of high amount of meat might cause colorectal cancer.

Isoflavones: chemistry, analysis, functions and effects on health and cancer

Isoflavones are phytoestrogens and natural plant compounds which are similar to 17-β-estradiol in chemical structure. It is known that they can act as estrogen agonists or antagonists, depending on endocrine estrogenic levels, but actions of isoflavones are rather complex due to large number of variables such as chemical structures and mechanisms. Some hypotheses on biological mechanisms have not satisfactorily been confirmed to date and human epidemiological and experimental studies have been relatively limited. Nevertheless, isoflavones and isoflavone rich foods have become a focus on interest due to positive health benefits on many diseases, especially prevention of hormone-related cancers, cardiovascular disease, osteoporosis, and adverse postmenopausal symptoms, and improvement of physiological condition such as maintaining cognitive function. This review provides an overview of chemistry, analytical techniques (focused on human biospecimens), functions including biological mechanisms, and effects of isoflavones, on the basis of the available meta-analysis and review articles and some original articles, on health and cancer.

Soy and breast cancer: focus on angiogenesis

Epidemiological studies have revealed that high consumption of soy products is associated with low incidences of hormone-dependent cancers, including breast and prostate cancer. Soybeans contain large amounts of isoflavones, such as the genistein and daidzain. Previously, it has been demonstrated that genistein, one of the predominant soy isoflavones, can inhibit several steps involved in carcinogenesis. It is suggested that genistein possesses pleiotropic molecular mechanisms of action including inhibition of tyrosine kinases, DNA topoisomerase II, 5α-reductase, galectin-induced G2/M arrest, protein histidine kinase, and cyclin-dependent kinases, modulation of different signaling pathways associated with the growth of cancer cells (e.g., NF-κB, Akt, MAPK), etc. Moreover, genistein is also a potent inhibitor of angiogenesis. Uncontrolled angiogenesis is considered as a key step in cancer growth, invasion, and metastasis. Genistein was found to inhibit angiogenesis through regulation of multiple pathways, such as regulation of VEGF, MMPs, EGFR expressions and NF-κB, PI3-K/Akt, ERK1/2 signaling pathways, thereby causing strong antiangiogenic effects. This review focuses on the antiangiogenic properties of soy isoflavonoids and examines their possible underlying mechanisms.

Biotransformed soybean extract induces cell death of estrogen-dependent breast cancer cells by modulation of apoptotic proteins

The process of soybean biotransformation increases the quantity of isoflavones (daidzein and genistein), which besides being considered an alternative to estroprogestive hormone replacement therapy (HRT), are able of hindering the growth and development of tumor cells. We investigated the effects of soybean extract biotransformed by fungus on estrogen-dependent (MCF-7) and nondependent (SK-BR-3) breast cell lines. Cells were treated with different concentrations of biotransformed (BSE) and nonbiotransformed soybean extract (SE), or daidzein (D) and genistein (G) patterns isolated and in combination (D + G). Afterwards, we analyzed cell viability by MTT assay, phosphatidylserine exposure and cell permeability by flow cytometry; expression of apoptotic proteins by Western blotting. BSE promoted reduction in cell viability and increase in DNA degradation in both cell lines. In addition, we verified increase in cell permeability and in the expression of phosphatidylserine, as well as modulation in the expression of apoptotic proteins in MCF-7 cells. The cells did not show any signs of cell death when incubated with the controls (D, G, and D + G). Unknown components found in the BSE induce cell death by apoptosis and necrosis, mainly in MCF-7 cells. These processes depend on the activation of caspase-3 and involve an increase in the expression of proapoptotic molecules.

Nutrient and nonnutrient components of legumes, and its chemopreventive activity: a review

Legumes in combination with other products are the staple food for a large part of the world population, especially the low-income fragment, because their seeds provide valuable amounts of carbohydrates, fiber, and proteins, and have an important composition of essential amino acids, the sulphured amino acids being the limiting ones. Furthermore, legumes also have nonnutritional compounds that may decrease the absorption of nutrients or produce toxic effects; however, it has been reported that depending on the dose, these nonnutritional compounds also have different bioactivities as antioxidant, hypolipidemic, hypoglycemic, and anticarcinogenic agents, which have been proven in scientific studies. It has been observed that in countries with a high consumption of legumes, the incidence of colorectal cancer is lower. Some studies have shown that legume seeds are an alternative chemopreventive therapy against various cancers especially colon; this was verified in various animal models of induced by azoxymethane, a colon specific carcinogenic compound, in which a diet was supplemented with different concentrations of beans, lentils, chickpeas, or soybeans, mostly. These studies have proven the anticancer activity of legumes in early stages of carcinogenesis. Therefore, it is important to review the information available to elucidate the chemopreventive mechanisms of action of legume compounds.

Dose-dependent effects of isoflavone exposure during early lifetime on the rat mammary gland: Studies on estrogen sensitivity, isoflavone metabolism, and DNA methylation

SCOPE

Isoflavone (ISO) exposure during adolescence modulates 17β-estradiol (E2) sensitivity of the adult mammary gland. The present study investigated the dose dependency of these effects focusing on proliferation, estrogen receptor dependent and independent gene expression, as well as DNA methylation and ISO metabolism.

METHODS AND RESULTS

Female Wistar rats were lifelong exposed to an ISO-depleted diet or to diets enriched with a soy ISO extract (ISO-rich diet (IRD)) causing plasma concentrations as observed minimally (IRDlow) and maximally (IRDhigh) in Asian women. The extract was characterized by both phytochemical analysis and E-Screen. Rats were ovariectomized at postnatal day (PND) 80 and treated with E2 from PND94 to 97. In contrast to uterine response, body weight and visceral fat mass were affected by ISO. In the mammary gland, both E2-induced proliferation (proliferating cell nuclear antigen staining) and estrogen receptor activation (progesterone receptor staining) were significantly reduced by IRDhigh but not by IRDlow, which however attenuated Gdf15 mRNA expression. DNA methylation analysis revealed significant differences in the promoter regions of Aldhl1, Extl1, and WAP between IRDhigh and ISO-depleted diet.

CONCLUSION

Lifelong exposure to ISO results in dose-dependent differential effects on proliferation, gene expression, and DNA methylation in rat mammary glands. Yet, a decrease in estrogen responsiveness was only achieved by IRDhigh.

Dietary phytochemical index and the risk of breast cancer: a case control study in a population of Iranian women

In this study we assessed the dietary phytochemical index in relation to the risk of breast cancer in women. This case-control study was conducted on 100 incident breast cancer cases and 175 healthy controls. Data regarding socio-demographic factors, medical history, medications, and anthropometric measurements were collected. Dietary data were obtained using a validated food frequency questionnaire and a energy-adjusted dietary phytochemical index (PI) was calculated. The odds ratios of breast cancer were assessed across energy- adjusted PI quartile categories. The mean age of participants was 46.2±8.9 and 45.9±9.4 years in cases and controls, respectively. The mean PI across quartile categories was 13.9±2.6, 21.1±1.8, 26.7±2.1, 41.6±10.2 in the first, second, third and fourth quartiles, respectively. After adjustment for all potential confounders, the risk of breast cancer in the forth quartile of dietary PI was significantly decreased (OR=0.08, 95%CI=0.01-0.84). Higher intake of phytochemical-rich foods is associated with lower risk of breast cancer.

Association between dietary factors and breast cancer risk among Chinese females: systematic review and meta-analysis

BACKGROUND

Evidence for associations between dietary factors and breast cancer risk is inconclusive among Chinese females. To evaluate this question, we conducted a systematic review of relevant case-control and cohort studies.

METHODS

Studies were systematically searched among 5 English databases (PudMed, ScienceDirect, Wiley, Clinicaltrials.gov, and Cochrane) and 3 Chinese databases (CNKI, WanFang, and VIP) until November 2012. Random effects models were used to estimate summary odds ratios (ORs) and the corresponding 95% confidence intervals (CIs).

RESULTS

Thirty one case-control studies and two cohort studies involving 9,299 cases and 11,413 controls were included. Consumption of both soy and fruit was significantly associated with decreased risk of breast cancer, with summary ORs of 0.65 (95% CIs: 0.43-0.99; I2=88.9%, P<0.001; N=13) and 0.66 (95% CIs: 0.47-0.91; I2=76.7%, P<0.001; N=7), respectively. Consumption of fat was significantly associated with increased risk of breast cancer (OR=1.36; 95% CIs: 1.13-1.63; I2=47.9%, P=0.088; N=6). There was non- significant association between consumption of vegetables and breast cancer risk (OR=0.72; 95% CIs: 0.51-1.02; I2= 74.4%, P<0.001; N=9). However, sensitivity analysis based on adjusted ORs showed decreased risk of breast cancer was also associated with consumption of vegetables (OR=0.49; 95% CIs: 0.30-0.67).

CONCLUSION

Both soy food and fruit are significantly associated with decreased risk of breast cancer among Chinese females, and vegetables also seems to be protective while dietary fatexerts a promoting influence.

Genetic and dietary determinants of insulin-like growth factor (IGF)-1 and IGF binding protein (BP)-3 levels among Chinese women

Background

Higher insulin-like growth factor (IGF)-1 and lower IGF binding protein (BP)-3 levels have been associated with higher commoncancer risk, including breast cancer. Dietary factors, genetic polymorphisms, and the combination of both may influence circulating IGF-1 and IGFBP-3 serum concentrations.

Methods

From September 2011 to July 2012, we collected demographic, reproductive and dietary data on 143 women (≥40 years). We genotyped IGF-1 rs1520220 and IGFBP-3 rs2854744 and measured circulating IGF-1 and IGFBP-3 levels in serum. Covariance analyses were used to estimate the associations of serum levels of IGF-1 and IGFBP-3, and the molar ratio of IGF-1to IGFBP-3 with IGF-1 rs1520220 and IGFBP-3 rs2854744 genotypes. We subsequently assessed the combined influence of genetics and diet (daily intake of protein, fat and soy isoflavones) on IGF-1 and IGFBP-3 levels.

Results

Among women aged less than 50 years, circulating IGF-1 serum levels were significantly lower for those with CC genotype for IGF-1 rs1520220 than levels for those with the GC or GG genotypes (in recessive model: P = 0.007).In gene-diet analyses among these women, we found carrying CC genotype for IGF-1 rs1520220 and high soy isoflavone intake tend to be associated with lower circulating IGF-1 levels synthetically (P = 0.002). Women with GG or GC genotypes for IGF-1 rs1520220 and with low intake of soy isoflavones had the highest levels of circulating IGF-1 (geometric mean [95% CI]: 195 [37, 1021] µg/L). Comparatively, women with both the CC genotype and high soy intake had the lowest levels of circulating IGF-1 (geometric mean [95% CI]: 120 [38,378] µg/L).

Conclusions

IGF-1 serum levels are significantly lower among women with the CC genotype for IGF-1-rs1520220. High soy isoflavone intake may interact with carrying CC genotype for IGF-1-rs1520220 to lower women's serum IGF-1 levels more.

Adolescent meat intake and breast cancer risk

The breast is particularly vulnerable to carcinogenic influences during adolescence due to rapid proliferation of mammary cells and lack of terminal differentiation. We investigated consumption of adolescent red meat and other protein sources in relation to breast cancer risk in the Nurses' Health Study II cohort. We followed prospectively 44,231 women aged 33-52 years who, in 1998, completed a detailed questionnaire about diet during adolescence. Relative risks (RR) and 95% confidence intervals (95%CI) were estimated using Cox proportional hazard regression. We documented 1132 breast cancer cases during 13-year follow-up. In multivariable Cox regression models with major breast cancer risk factors adjustment, greater consumption of total red meat in adolescence was significantly associated with higher premenopausal breast cancer risk (highest vs. lowest quintiles, RR, 1.43; 95%CI, 1.05-1.94; Ptrend  = 0.007), but not postmenopausal breast cancer. Adolescent intake of poultry was associated with lower risk of breast cancer overall (RR, 0.76; 95%CI, 0.60-0.97; for each serving/day). Adolescent intakes of iron, heme iron, fish, eggs, legumes and nuts were not associated with breast cancer. Replacement of one serving/day of total red meat with one serving of combination of poultry, fish, legumes, and nuts was associated with a 15% lower risk of breast cancer overall (RR, 0.85; 95%CI, 0.74-0.96) and a 23% lower risk of premenopausal breast cancer (RR, 0.77; 95%CI, 0.64-0.92). In conclusion, higher consumption of red meat during adolescence was associated with premenopausal breast cancer. Substituting other dietary protein sources for red meat in adolescent diet may decrease premenopausal breast cancer risk.

Evidence for an association of dietary flavonoid intake with breast cancer risk by estrogen receptor status is limited

BACKGROUND

Results from preclinical studies suggest that flavonoids, which are ubiquitous in plant-based diets, lower breast cancer risk. Epidemiologic studies of flavonoid intake and breast cancer risk, however, are limited, and few investigated associations with the more aggressive estrogen receptor (ER)-negative (ER-) tumors.

OBJECTIVE

We examined the associations between 7 subclasses of dietary flavonoids and invasive postmenopausal breast cancer risk overall and by ER status in a U.S. prospective cohort.

METHODS

In 1999-2000, 56,630 postmenopausal women completed detailed self-administered questionnaires, among whom 2116 invasive breast cancers were verified during a mean follow-up period of 8.5 y. Cox proportional hazards regression was used to calculate multivariable-adjusted HRs and 95% CIs.

RESULTS

Total flavonoid intake was not associated with breast cancer risk. However, there was a modest inverse association between flavone intake and overall breast cancer risk (fifth vs. first quintile HR: 0.88; 95% CI: 0.76, 1.01; P-trend = 0.04) and between flavan-3-ol intake and risk of ER- breast cancer (for an increment of 40 mg/d; HR: 0.81; 95% CI: 0.67, 0.97) but not for ER-positive (ER+) breast cancer risk.

CONCLUSION

The inverse association of flavan-3-ol intake with ER- but not ER+ breast cancer is consistent with other studies that suggest a beneficial role of plant-based diets in ER- breast cancer risk.

Dietary isoflavone intake is not statistically significantly associated with breast cancer risk in the Multiethnic Cohort

Given the high intake levels of soya and low incidence rates of breast cancer in Asian countries, isoflavones, substances with an oestrogen-like structure occurring principally in soyabeans, are postulated to be cancer protective. In the present study, we examined the association of dietary isoflavone intake with breast cancer risk in 84,450 women (896 in situ and 3873 invasive cases) who were part of the Multiethnic Cohort (Japanese Americans, whites, Latinos, African Americans and Native Hawaiians) with a wide range of soya intake levels. The absolute levels of dietary isoflavone intake estimated from a baseline FFQ were categorised into quartiles, with the highest quartile being further subdivided to assess high dietary intake. The respective intake values for the quartiles (Q1, Q2, Q3, and lower and upper Q4) were 0-< 3·2, 3·2-< 6·7, 6·7-< 12·9, 12·9-< 20·3, and 20·3-178·7 mg/d. After a mean follow-up period of 13 years, hazard ratios (HR) and 95% CI were calculated using Cox regression models stratified by age and adjusted for known confounders. Linear trends were tested by modelling continuous variables of interest assigned the median value within the corresponding quartile. No statistically significant association was observed between dietary isoflavone intake and overall breast cancer risk (HR for upper Q4 v. Q1: 0·96 (95% CI 0·85, 1·08); P trend = 0·40). While the test for interaction was not significant (P=0·14), stratified analyses suggested possible ethnic/racial differences in risk estimates, indicating that higher isoflavone intakes may be protective in Latina, African American and Japanese American women. These results are in agreement with those of previous meta-analyses showing no protection of isoflavones at low intake levels, but suggesting inverse associations in populations consuming high amounts of soya.

A hypothesis regarding the molecular mechanism underlying dietary soy-induced effects on seizure propensity

Numerous neurological disorders including fragile X syndrome, Down syndrome, autism, and Alzheimer’s disease are co-morbid with epilepsy. We have observed elevated seizure propensity in mouse models of these disorders dependent on diet. Specifically, soy-based diets exacerbate audiogenic-induced seizures in juvenile mice. We have also found potential associations between the consumption of soy-based infant formula and seizure incidence, epilepsy comorbidity, and autism diagnostic scores in autistic children by retrospective analyses of medical record data. In total, these data suggest that consumption of high levels of soy protein during postnatal development may affect neuronal excitability. Herein, we present our theory regarding the molecular mechanism underlying soy-induced effects on seizure propensity. We hypothesize that soy phytoestrogens interfere with metabotropic glutamate receptor signaling through an estrogen receptor-dependent mechanism, which results in elevated production of key synaptic proteins and decreased seizure threshold.

Polyphenols and the human brain: plant “secondary metabolite” ecologic roles and endogenous signaling functions drive benefits

Flavonoids and other polyphenols are ubiquitous plant chemicals that fulfill a range of ecologic roles for their home plant, including protection from a range of biotic and abiotic stressors and a pivotal role in the management of pathogenic and symbiotic soil bacteria and fungi. They form a natural part of the human diet, and evidence suggests that their consumption is associated with the beneficial modulation of a number of health-related variables, including those related to cardiovascular and brain function. Over recent years, the consensus as to the mechanisms responsible for these effects in humans has shifted away from polyphenols having direct antioxidant effects and toward their modulation of cellular signal transduction pathways. To date, little consideration has been given to the question of why, rather than how, these plant-derived chemicals might exert these effects. Therefore, this review summarizes the evidence suggesting that polyphenols beneficially affect human brain function and describes the current mechanistic hypotheses explaining these effects. It then goes on to describe the ecologic roles and potential endogenous signaling functions that these ubiquitous phytochemicals play within their home plant and discusses whether these functions drive their beneficial effects in humans via a process of “cross-kingdom” signaling predicated on the many conserved similarities in plant, microbial, and human cellular signal transduction pathways.

The effects of soy supplementation on gene expression in breast cancer: a randomized placebo-controlled study

BACKGROUND

There are conflicting reports on the impact of soy on breast carcinogenesis. This study examines the effects of soy supplementation on breast cancer-related genes and pathways.

METHODS

Women (n = 140) with early-stage breast cancer were randomly assigned to soy protein supplementation (n = 70) or placebo (n = 70) for 7 to 30 days, from diagnosis until surgery. Adherence was determined by plasma isoflavones: genistein and daidzein. Gene expression changes were evaluated by NanoString in pre- and posttreatment tumor tissue. Genome-wide expression analysis was performed on posttreatment tissue. Proliferation (Ki67) and apoptosis (Cas3) were assessed by immunohistochemistry.

RESULTS

Plasma isoflavones rose in the soy group (two-sided Wilcoxon rank-sum test, P < .001) and did not change in the placebo group. In paired analysis of pre- and posttreatment samples, 21 genes (out of 202) showed altered expression (two-sided Student's t-test, P < .05). Several genes including FANCC and UGT2A1 revealed different magnitude and direction of expression changes between the two groups (two-sided Student's t-test, P < .05). A high-genistein signature consisting of 126 differentially expressed genes was identified from microarray analysis of tumors. This signature was characterized by overexpression (>2-fold) of cell cycle transcripts, including those that promote cell proliferation, such as FGFR2, E2F5, BUB1, CCNB2, MYBL2, CDK1, and CDC20 (P < .01). Soy intake did not result in statistically significant changes in Ki67 or Cas3.

CONCLUSIONS

Gene expression associated with soy intake and high plasma genistein defines a signature characterized by overexpression of FGFR2 and genes that drive cell cycle and proliferation pathways. These findings raise the concerns that in a subset of women soy could adversely affect gene expression in breast cancer.

Measuring exposure to the polyphenol metabolome in observational epidemiologic studies: current tools and applications and their limits

Much experimental evidence supports a protective role of dietary polyphenols against chronic diseases such as cardiovascular diseases, diabetes, and cancer. However, results from observational epidemiologic studies are still limited and are often inconsistent. This is largely explained by the difficulties encountered in the estimation of exposure to the polyphenol metabolome, which is composed of ~500 polyphenols distributed across a wide variety of foods and characterized by diverse biological properties. Exposure to the polyphenol metabolome in epidemiologic studies can be assessed by the use of detailed dietary questionnaires or the measurement of biomarkers of polyphenol intake. The questionnaire approach has been greatly facilitated by the use of new databases on polyphenol composition but is limited by bias as a result of self-reporting. The use of polyphenol biomarkers holds much promise for objective estimation of polyphenol exposure in future metabolome-wide association studies. These approaches are reviewed and their advantages and limitations discussed by using examples of epidemiologic studies on polyphenols and cancer. The current improvement in these techniques, along with greater emphasis on the intake of individual polyphenols rather than polyphenols considered collectively, will help unravel the role of these major food bioactive constituents in disease prevention.

Dietary factors affecting polyphenol bioavailability

While many epidemiological studies have associated the consumption of polyphenols within fruits and vegetables with a decreased risk of developing several chronic diseases, intervention studies have generally not confirmed these beneficial effects. The reasons for this discrepancy are not fully understood but include potential differences in dosing, interaction with the food matrix, and differences in polyphenol bioavailability. In addition to endogenous factors such as microbiota and digestive enzymes, the food matrix can also considerably affect bioaccessibility, uptake, and further metabolism of polyphenols. While dietary fiber (such as hemicellulose), divalent minerals, and viscous and protein-rich meals are likely to cause detrimental effects on polyphenol bioaccessibility, digestible carbohydrates, dietary lipids (especially for hydrophobic polyphenols, e.g., curcumin), and additional antioxidants may enhance polyphenol availability. Following epithelial uptake, polyphenols such as flavonoids may reduce phase II metabolism and excretion, enhancing polyphenol bioavailability. Furthermore, polyphenols may act synergistically due to their influence on efflux transporters such as p-glycoprotein. In order to understand polyphenol bioactivity, increased knowledge of the factors affecting polyphenol bioavailability, including dietary factors, is paramount.

Helping women to good health: breast cancer, omega-3/omega-6 lipids, and related lifestyle factors

In addition to genetic predisposition and sex hormone exposure, physical activity and a healthy diet play important roles in breast cancer (BC). Increased intake of omega-3 fatty acids (n-3) associated with decreased omega-6 (n-6), resulting in a higher n-3/n-6 ratio compared with the western diet, are inversely associated with BC risk, as shown by Yang et al. in their meta-analysis in BMC Cancer. High consumption of polyphenols and organic foods increase the n-3/n-6 ratio, and in turn may decrease BC risk. Intake of high fiber foods and foods with low glycemic index decreases insulin resistance and diabetes risk, and in turn may decrease BC risk. The modernized Mediterranean diet is an effective strategy for combining these recommendations, and this dietary pattern reduces overall cancer risk and specifically BC risk. High-risk women should also eliminate environmental endocrine disruptors, including those from foods. Drugs that decrease the n-3/n-6 ratio or that are suspected of increasing BC or diabetes risk should be used with great caution by high-risk women and women wishing to decrease their BC risk.Please see related article: http://www.biomedcentral.com/1471-2407/14/105/abstract.

Higher dietary folate intake reduces the breast cancer risk: a systematic review and meta-analysis

Background:

Many epidemiological studies have investigated the association between folate intake, circulating folate level and risk of breast cancer; however, the findings were inconsistent between the studies.

Methods:

We searched the PubMed and MEDLINE databases updated to January, 2014 and performed the systematic review and meta-analysis of the published epidemiological studies to assess the associations between folate intake level, circulating folate level and the overall risk of breast cancer.

Results:

In all, 16 eligible prospective studies with a total of 744 068 participants and 26 205 breast cancer patients and 26 case–control studies with a total of 16 826 cases and 21 820 controls that have evaluated the association between folate intake and breast cancer risk were identified. Pooled analysis of the prospective studies and case–control studies suggested a potential nonlinearity relationship for dietary folate intake and breast cancer risk. Prospective studies indicated a U-shaped relationship for the dietary folate intake and breast cancer risk. Women with daily dietary folate intake between 153 and 400 μg showed a significant reduced breast cancer risk compared with those <153 μg, but not for those >400 μg. The case–control studies also suggested a significantly negative correlation between the dietary folate intake level and the breast cancer risk. Increased dietary folate intake reduced breast cancer risk for women with higher alcohol intake level, but not for those with lower alcohol intake. No significant association between circulating folate level and breast cancer risk was found when the results of 8 identified studies with 5924 participants were pooled.

Conclusions:

Our studies suggested that folate may have preventive effects against breast cancer risk, especially for those with higher alcohol consumption level; however, the dose and timing are critical and more studies are warranted to further elucidate the questions.

Association between soy isoflavone intake and breast cancer risk for pre- and post-menopausal women: a meta-analysis of epidemiological studies

Background

Conclusions drawn from meta-analyses on the association between soy isoflavone intake and breast cancer risk for pre- and post-menopausal women are not fully consistent. These meta-analyses did not explore the influence of different study designs on the pooled results on the basis of distinguishing between pre- and post-menopausal women.

Methodology and Principal Findings

We performed a meta-analysis of 35 studies which reported results of association between soy isoflavone intake and breast cancer risk for pre- and/or post-menopausal women, calculated pooled odds ratios and their 95% confidence intervals of pre- and post-menopausal women respectively, and further explored soy isoflavone-breast cancer association on the basis of considering different study regions and designs. Summary results suggested that soy isoflavone intake has a protective effect against breast cancer for both pre- and post-menopausal women. However, they are influenced by study design and region. Pooled ORs of studies carried out in Asian countries suggested that soy isoflavone’s protective effect exist in both pre- and post-menopausal women (OR = 0.59, 95%CI: 0.48–0.69 for premenopausal women; OR = 0.59, 95%CI: 0.44–0.74 for postmenopausal women). However, there are some differences between the results pooled from different study designs for women in Asian countries (test for consistency, P = 0.04). Pooled OR of studies on postmenopausal women in Western countries suggested that soy isoflavone intake has a marginally significant protective effect (OR = 0.92; 95%CI: 0.83∼1.00), but further analyses stratifying by study design found no statistically significant association.

Conclusions

We meta-analyzed more and newer research results, and separated women according to menopausal status to explore soy isoflavone-breast cancer association. We founded that soy isoflavone intake could lower the risk of breast cancer for both pre- and post-menopausal women in Asian countries. However, for women in Western countries, pre- or post-menopausal, there is no evidence to suggest an association between intake of soy isoflavone and breast cancer.

Effects of tomato and soy on serum adipokine concentrations in postmenopausal women at increased breast cancer risk: a cross-over dietary intervention trial

CONTEXT

Breast cancer risk among postmenopausal women increases as body mass index increases. Practical preventive methods to reduce risk of breast cancer are lacking. Few studies have investigated the effects of carotenoids and isoflavones on circulating adipokines in postmenopausal women.

OBJECTIVE

The aim was to examine the effects of lycopene- and isoflavone-rich diets on serum adipokines.

DESIGN

This was a 26-week, two-arm, longitudinal crossover trial.

SETTING

Participants were recruited from clinics at The Ohio State University Comprehensive Cancer Center.

PARTICIPANTS

Seventy postmenopausal women at increased breast cancer risk participated in the study. The mean age and body mass index of participants was 57.2 years and 30.0 kg/m(2), respectively; the study was comprised of 81.4% whites.

INTERVENTIONS

The interventions included 10 weeks of consumption of a tomato-based diet (≥25 mg lycopene daily) and 10 weeks of consumption of a soy-based diet (≥40 g of soy protein daily), with a 2-week washout in between.

MAIN OUTCOME MEASURES

Changes in serum adiponectin, leptin, and the adiponectin to leptin ratio were examined for each intervention through linear mixed models, with ratio estimates corresponding to postintervention adipokine concentrations relative to preintervention concentrations.

RESULTS

After the tomato intervention, among all women, adiponectin concentration increased (ratio 1.09, 95% confidence interval (CI) 1.00-1.18), with a stronger effect observed among nonobese women (ratio 1.13, 95% CI 1.02-1.25). After the soy intervention, adiponectin decreased overall (ratio 0.91, 95% CI 0.84-0.97), with a larger reduction observed among nonobese women (ratio 0.89, 95% CI 0.81-0.98). Overall, no significant changes in leptin or the adiponectin to leptin ratio were observed after either intervention.

CONCLUSIONS

Increasing dietary consumption of tomato-based foods may beneficially increase serum adiponectin concentrations among postmenopausal women at increased breast cancer risk, especially those who are not obese. Additional studies are essential to confirm these effects and to elucidate the specific mechanisms that may make phytonutrients found in tomatoes practical as breast cancer chemopreventive agents.