Soybean Isoflavones in Bone Health

ArticleinForum of nutrition 61:104-16 · February 2009with13 Reads
DOI: 10.1159/000212743 · Source: PubMed
Abstract
Soybean isoflavones are structurally similar to estrogen, bind to estrogen receptors, and exhibit weak estrogenic activity. It has been reported that isoflavones play an important role in the prevention of hormone-dependent diseases, including osteoporosis, cardiovascular diseases, cancer, and postmenopausal syndrome. There are many researches indicating isoflavones prevent bone loss caused by estrogen deficiency in animal models. Furthermore, it has been demonstrated that a combination of isoflavone treatment and exercise cooperatively prevented bone loss in the estrogen-deficient status. Epidemiological studies demonstrated the relationship between the lower incidence of osteoporosis in Asian women and a diet rich in soy foods. Although a number of observational studies confirm the findings from the animal studies, the results from intervention studies are still controversial. One of the potential reasons for these inconsistencies could be individual differences in the isoflavone metabolism. Recently, it has been suggested that the clinical effectiveness of isoflavones might partly depend on the ability to produce equol, a gut bacterial metabolite of daidzein showing stronger estrogenic activity than the predominant isoflavones. Several candidate bacteria responsible for equol production have been suggested, for example Lactococcus 20-92 strain. From these findings, food factors enhancing equol production have received great deal of attention recently. On the other hand, safety assessment of isoflavones has been conducted by the Japanese Food Safety Commission. Further studies are required to address the numerous questions on the potential benefits, mechanisms of action, and safety of isoflavones.
    • "Several studies have demonstrated that in comparison with animal protein, soy protein decreases urinary calcium loss, due to lower sulfurcontaining amino acid and higher potassium content of soy protein [18]. The favorable effects of soybeans on bones may be related also to its isoflavones, which exhibit mild estrogenic activity [19]. In this context, a clinical study has shown that soy protein/isoflavones intake significantly increased bone mineral density and content in early postmenopausal Chinese women [20]. "
    [Show abstract] [Hide abstract] ABSTRACT: Open Access Full Text Article based diets have been suggested to have a greater negative effect on bones than plant protein-based diets do, because animal proteins e.g.beef, chicken, fish and eggs are acid forming food, due to the metabolic oxidation of the sulfur-containing amino acids (methionine and cysteine) to sulfate moiety leading to shifting of blood pH to acidic side.This in turn affects the overall dietary acid-base balance and ultimately contributes to buffering response by the skeleton in the form of mobilization of carbonate and citrate salts from bone matrix in order to balance the endogenous acids generated from animal proteins [8]. Small decreases in blood pH have been reported to activate bone resorption [9]. Furthermore, in vitro study has indicated that acidosis can directly stimulate osteoclastic activity and inhibit osteoblastic activity [10]. Dietary acid load associated with excessive intake of animal protein can adversely affect bone metabolism indirectly via inducing alterations of endocrine function. The hypercorticoid response to metabolic acidosis has been reported in rats [11]. Moreover, Maurer et al demonstrated that western diet-induced mild acidosis was accompanied with increased excretion of cortisol leading to higher plasma levels in young human adults [12]. Evidence showed that even a mild increase in cortisol levels would contribute to increased fracture risk [13]. Another consequence of protein-induced acidosis is the urinary calcium excretion which is strongly related to the net renal acid excretion.Overconsumption of animal proteins was associated with urinary calcium loss [9]. Earlier study has demonstrated that urinary excretion of calcium was positively correlated with animal protein intake in middle aged and elderly Japanese population [14]. Interestingly, short term-neutralization of acid load associated with western diet by carbonate salt significantly attenuated the urinary calcium excretion and suppressed the biochemical markers of bone resorption in young adult subjects [12].
    Full-text · Article · Oct 2014 · Asian Pacific journal of cancer prevention: APJCP
    • "These compounds have the ability to bind to estrogen receptors and exert various estrogenic and antiestrogenic effects (Branca 2003; Usui 2006). Epidemiological studies and clinical trials have shown that phytoestrogens have a protective effect against postmenopausal symptoms; cardiovascular disease; bone health problems; breast, prostate, and colon cancers; and postmenopausal syndrome due to their structural similarity to estrogen (Bhathena and Velasquez 2002; Duncan et al. 2003; Ishimi 2009; Messina 1999; Setchell and Cassidy 1999). This review article discusses the role of metabolites of phytoestrogens that have been hydrolyzed by probiotics or intestinal microflora and how such metabolism improves the actions of these phytoestrogens in mimicking mammalian estrogens, thereby preventing postmenopausal bone loss. "
    [Show abstract] [Hide abstract] ABSTRACT: Phytoestrogens are a class of bioactive compounds derived from plants and exert various estrogenic and antiestrogenic effects. Estrogen deficiency osteoporosis has become a serious problem in elderly women. The use of ovariectomized (OVX) rat or mice models to simulate the postmenopausal condition is well established. This review aimed to clarify the sources, biochemistry, absorption, metabolism, and mode of action of phytoestrogens on bone health in intervention studies. In vitro, phytoestrogens promote protein synthesis, osteoprotegerin/receptor activation of nuclear factor-kappa B ligand ratio, and mineralization by osteoblast-like cells (MC3T3-E1). In the OVX murine model, administration of phytoestrogens can inhibit differentiation and activation of osteoclasts, expression of tartrate-resistant acid phosphatase, and secretion of pyridinoline compound. Phytoestrogens also enhance bone formation and increase bone mineral density and levels of alkaline phosphatase, osteocalcin, osteopontin, and α1(I) collagen. Results of mechanistic studies have indicated that phytoestrogens suppress the rate of bone resorption and enhance the rate of bone formation.
    Full-text · Article · Jan 2013
    • "The soy food intake among Chinese women is substantially higher than that in other countries, with about 48 grams/day in Chinese population (Horn-Ros, 2003). The soy constituents have been observed to have anticancer properties (Adlercreutz et al., 1997; Mouridsen et al., 2003; Lee et al., 2009; Taylor, 2009) and could improve cardiovascular and bone health (Clarkson, 2002; Ishimi, 2009). Previous in vivo and in vitro studies regarding the role of soy constituents could stimulate cell proliferation. "
    [Show abstract] [Hide abstract] ABSTRACT: Soy foods are the major source of isoflavones, which are believed to play important roles in genesis of breast cancer and its progression. We here conducted a prospective study to evaluate the association of soy isoflavone food consumption with breast cancer prognosis. A prospective study was performed from January 2004 and January 2006 in China. Trained interviewers conducted face-to-face interviews using a structured questionnaire to collect information on dietary habits and potential confounding factors. The relative risk [hazard ratio (HR)] and 95% CI were calculated from the Cox regression model for all significant predictors from cancer diagnosis to the endpoint of the study (event). After a median follow up of 52.1 months (range, 9-60 months), a total of 79 breast cancer related deaths were recorded in our study, risk being inversely associated with a high intake of soy isoflavone. With an average intake of soy isoflavone above 17.3 mg/day, the mortality of breast cancer can be reduced by about 38-36%. We also found the decreased breast cancer death with high soy protein intake, with a HR (95% CI) of 0.71 (0.52-0.98). Stratified analysis with reference to the ER status, further demonstrated a better prognosis of ER positive breast cancer with a high intake of soy isoflavone (HR 0.59, 0.40-0.93). Our study shows the soy food intake is associated with longer survival and low recurrence among breast cancer patients. A cohort study with a larger sample size and long term follow-up is now needed.
    Article · Feb 2012
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