The most recent findings on soy and isoflavones were presented in Washington DC on the occasion of the 9th International Symposium on the Role of Soy in Health Promotion and Chronic Disease Prevention and Treatment (October 16-19, 2010). A major part of the topics was dedicated to safety and health benefits in menopausal women, and to the issue of soy and breast cancer.
Please note that the data presented in this symposium only refers to the most recent publications on the topic. Since the Milan soy safety symposium in May 2009 further publications have appeared with data which was not presented in Washington. None of the new bibliographic findings contradicts the positive image relating health benefits and safety of application of isoflavone-containing preparations supplemented by menopausal women.
The most recent data on soy and breast cancer presented in this symposium confirms that
- - for pharmacokinetic reasons the risks experimentally derived from the model of ovariectomized rats cannot simply be extrapolated to humans;
- - cancer protective effects may be expected through an improvement of the metabolic ratio of estrone metabolites;
- - breast cancer patients may expect an improved disease-free survival time by switching their diet to a soy and isoflavone-rich food;
- - the application of tamoxifen or anastrozole is not disturbed by isoflavones – in contrast, synergistic effects may rather be expected; and
- - even in high risk patients an increased risk of breast cancer is not to be expected.
Further safety data was generated in the clinical trials related to bone health and menopausal complaints presented in this symposium. In none of these studies a risk of any kind at hormone-sensitive tissues could be evidenced.
The pertinent clinical data covers a time of application of more than 5 years. Even if the issue of protective effects in the sense of a prevention of estrogen-sensitive tumours is still not conclusively answered, the hypothesis whether isoflavones might actually increase the risk can by now be refuted, based on the background of ample clinical data.
With the confirmation in yet another systematic meta-analysis the effects of isoflavones against menopausal hot flushes can no longer be doubted. This conclusion is also supported by newly presented clinical data. Likewise accumulating is the evidence pointing to protective effects of isoflavones at the bones of menopausal women. In the course of the symposium protective effects of isoflavones at the cardiovascular system were likewise amply presented. An important aspect is that none of the analyzed or newly presented trials in menopausal women yielded hints to adverse events in hormone-sensitive tissues (breast or uterus).
Presentations on the Washington symposium on health benefits and safety of application of soy and isoflavones:
Mark Messina: Overview over the controversy on soy and breast cancer
Stephen Barnes: Short introduction to equol
Belinda Jenks: Safety assessment of natural S-Equol
Nadine Brown: Isoflavones protect against chemically induced cancer in animal experiments
Mary Hardy: Soy and breast cancer patients – the clinical perspective
Xiao Ou Shu: Soy food improves survival rates in tamoxifen-treated breast cancer patients
Xinmei Kang: Isoflavones reduce the recurrence rate in anastrozole-treated breast cancer patients
Mindy Kurzer: Isoflavones are clearly efficacious against menopausal hot flushes – a meta-analysis
James Anderson: Soy protein decreases blood lipids – a meta-analysis
David Jenkins: The blood lipid lowering effects of soy protein are clinically important
Stephen L. Atkin: Can isoflavones deteriorate a subclinical hypothyreoidism?
Safety 