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1: J Nutr. 2009 May;139(5):981-6. Epub 2009 Mar 25.
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Various doses of soy isoflavones do not modify mammographic density in postmenopausal women.
Cancer Research Center of Hawaii, Honolulu, HI 96813, USA. gertraud@crch.hawaii.edu
Soy isoflavones have functional similarity to human estrogens and may protect against breast cancer as a result of their antiestrogenic activity or increase risk as a result of their estrogen-like properties. We examined the relation between isoflavone supplementation and mammographic density, a strong marker for breast cancer risk, among postmenopausal women. The Osteoporosis Prevention Using Soy (OPUS) study, a multi-site, randomized, double-blinded, and placebo-controlled trial assigned 406 postmenopausal women to 80 or 120 mg/d of isoflavones each or a placebo for 2 y. Percent densities were assessed in digitized mammograms using a computer-assisted method. The mammogram reader did not know the treatment status and the time of mammograms. We applied mixed models to compare breast density by treatment while considering the repeated measures. The mammographic density analysis included 358 women, 88.2% of the OPUS participants; 303 had a complete set of 3 mammograms, 49 had 2, and 6 had only 1 mammogram. At baseline, the groups were similar in age, BMI, and percent density, but mean breast density differed by study site (P = 0.02). A model with all mammograms did not show a treatment effect on any mammographic measure, but the change over time was significant; breast density decreased by 1.6%/y across groups (P < 0.001). Stratification by age and BMI did not reveal any effects in subgroups. In this randomized 2-y trial, isoflavone supplements did not modify breast density in postmenopausal women. These findings offer reassurance that isoflavones do not act like hormone replacement medication on breast density.
PMID: 19321587 [PubMed – indexed for MEDLINE]
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1: J Clin Endocrinol Metab. 2008 Dec;93(12):4787-96. Epub 2008 Sep 16.
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Breast safety and efficacy of genistein aglycone for postmenopausal bone loss: a follow-up study.
Department of Biochemical, Physiological and Nutritional Sciences, Section of Physiology and Human Nutrition, University of Messina, 98125 Messina, Italy.
CONTEXT: Genistein aglycone improves bone metabolism in women. However, questions about the long-term safety of genistein on breast as well as its continued efficacy still remain. OBJECTIVE: We assessed the continued safety profile of genistein aglycone on breast and endometrium and its effects on bone after 3 yr of therapy. DESIGN: The parent study was a randomized, double-blind, placebo-controlled trial involving 389 osteopenic, postmenopausal women for 24-months. Subsequently, a subcohort (138 patients) continued therapy for an additional year. Patients and Interventions: Participants received 54 mg of genistein aglycone daily (n = 71) or placebo (n = 67). Both treatment arms received calcium and vitamin D(3) in therapeutic doses. MAIN OUTCOMES: Mammographic density was assessed at baseline, 24 and 36 months by visual classification scale and digitized quantification. BRCA1 and BRCA2, sister chromatid exchange, and endometrial thickness were also evaluated. Lumbar spine and femoral neck bone mineral density were also assessed. Secondary outcomes were biochemical levels of bone markers. RESULTS: After 36 months, genistein did not significantly change mammographic breast density or endometrial thickness, BRCA1 and BRCA2 expression was preserved, whereas sister chromatid exchange was reduced compared with placebo. Bone mineral density increases were greater with genistein for both femoral neck and lumbar spine compared to placebo. Genistein also significantly reduced pyridinoline, as well as serum carboxy-terminal cross-linking telopeptide and soluble receptor activator of NF-kappaB ligand while increasing bone-specific alkaline phosphatase, IGF-I, and osteoprotegerin levels. There were no differences in discomfort or adverse events between groups. CONCLUSIONS: After 3 yr of treatment, genistein exhibited a promising safety profile with positive effects on bone formation in a cohort of osteopenic, postmenopausal women.
PMID: 18796517 [PubMed – indexed for MEDLINE]
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1: Toxicol In Vitro. 2008 Sep;22(6):1452-60. Epub 2008 May 4.
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Effects of soy isoflavones on 17beta-estradiol-induced proliferation of MCF-7 breast cancer cells.
Center of Private Clinic and Clinical Studies MED 19, Armbrustergasse 1, Vienna, Austria.
Based on the results of in vitro-experiments in practically estrogen-free media and in the absence of estrogen-beta receptors, soy isoflavones have been suspected to enhance proliferation of MCF-7 breast cancer cells. In this study the effects of soy isoflavones on MCF-7 cells were investigated in the presence and absence of estrogen, directly and in a metabolized form by testing sera of postmenopausal women supplemented with isoflavones. First, three concentrations of isoflavones (0.1, 1 and 10 mumol/l) were tested at increasing levels of 17-beta-estradiol (<10 pM, 50, 100 and 500 pM). Next, blood sera from women supplemented for two weeks either with 200mg isoflavones or with 2 mg 17-beta-estradiol per day, or the combination of both were investigated in an MCF-7 cell proliferation assay. Further, the samples were screened for changes in gene expression patterns of the MCF-7 cells with Gene Chip arrays. Only at unphysiologically low estrogen levels isoflavones led to minor proliferation-enhancing effects. In contrast, at estradiol levels of >20 pM, isoflavones both tested directly and indirectly (metabolized) revealed significant anti-proliferative effects as well as in the proliferation and the gene chip assay. These findings emphasize the reported advantageous properties of isoflavones for postmenopausal women.
PMID: 18554862 [PubMed – indexed for MEDLINE]