July 2007, Volume 7, Issue 1: "Studies on the Influence of Dietary Isoflavones, Daidzein and Genistein, in Chemical Mutagenesis and Tumor Development in Female Rats"
Issue 1 of Volume 7 of the Regulatory Research Perspectives: Impact on Public Health.
Introduction Paragraph for current issue:
Hormone replacement therapy (HRT) in women has been shown to confer several benefits, including a reduction of hot flashes during menopause. However, HRT has also been linked to increased risks for heart attack, stroke, and breast cancer. To avoid the potentially harmful side effects of HRT, many women are switching to alternative sources of estrogens, such as the isoflavone phytoestrogens, in the belief that naturally occurring substances may be safer than HRT. There is a large body of compelling evidence showing the health benefits of isoflavones. Our Western lifestyle does not normally permit the consumption of soy foods adequate to meet health needs. Thus, many women ingest dietary supplements of phytoestrogens on a regular basis to forestall the complications of menopause. Two of the most commonly ingested isoflavones are daidzein (DZ) and genistein (GE). Both are major components of soy isoflavones and are presumed to be responsible for their health-promoting effects.
It is possible that these compounds may also be toxic. In theory, the naturally occurring isoflavones can alter the metabolism of endogenous hormones and, thus, influence the pathogenesis of hormone-dependent cancers. Early studies have shown that both DZ and GE are mutagenic, indicating that isoflavones may play some role in tumor mutagenesis. The present study examines the mutagenic activity in the whole animal of the carcinogen 7, 12-dimethylbenz(α)anthracene (DMBA). The sensitive Big Blue (BB) mice and rats were used to detect mutations in several organs. In addition, the BB rats were ovariectomized to model menopause. The effects of feeding DZ, GE, and 17β-estradiol on the genotoxicity and tumorigenicity of DMBA in estrogen-responsive tissues were determined. The results help provide a basis for future risk assessment strategies for phytoestrogens.
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