The safety of application and the benefits of isoflavones for postmenopausal women were the focus of a symposium organised by the CRN (Council for Responsible Nutrition), which took place on the 13th and 14th of May 2009 in Milan (Italy) under active participation of the EFSA (European Food Safety Authority).
A recently published meta-analysis presented on the symposium examined the range of adverse effects of isoflavone-containing preparations (Tempfer et al. 2009). Prof. Clemens Tempfer of the Department of Gynaecology of the University Hospital of Vienna (Austria) identified 174 clinical trials with a total of 9,629 participating women (Tempfer 2009). 92 of these trials made specific reference to the assessment of adverse events. The focus of the evaluation was on the observation of potential estrogenic effects, the stimulation of cancer and interactions with tamoxifen. Adverse events were classified into gastrointestinal symptoms, hormone-related events (menstrual bleedings, breast- or endometrial carcinoma or endometrial hyperplasia), complaints of the musculoskeletal system, neurologic observations, and non-specific events. With the exception of gastrointestinal complaints none of the chosen categories showed a significant difference between isoflavone intake and placebo – including the hormonal effects. Gastrointestinal complaints were responsible for 17 % of events in the isoflavone group, but only for 13 % in the placebo group (Tempfer et al. 2009). According to Prof. Temper this evaluation underlines a high level of safety for isoflavone-containing supplements.
Conclusions for safety of application
The overall data and especially the latest studies regarding the human safety of application – among them long-term trials with highly dosed isoflavones – contradict the hypothetical risk extrapolated from animal experiments of questionable relevance. This is especially true for the postulated risk of postmenopausal women with an elevated risk of breast cancer. It is time to give preference to the overwhelming mass of clinical proofs of safety of application over debates on theoretical risks based on animal experimentation. The health benefits, e.g. against menopausal complaints, which can by now no longer be denied speak in favour of an isoflavone-rich nutrition.
Further reports from the Milan 2009 Soy Safety Symposium:
2. Facts Related to Bioavailability
3. Lack of relevance of animal models for an extrapolation of risks of isoflavones
4. Isoflavones protect „menopausal” mice from breast cancer
5. Breast cancer risk is increased by synthetic gestagens
6. Breast tissue density remains unaltered with soy
7. Clinical studies demonstrate safety of soy in the breast
8. Study in more than 5,000 breast cancer patients: First positive tendencies with soy!
9. No effects of isoflavones on the endometrium
10. Isoflavones also safe at the thyroid gland
11. Backgrounds on Menopausal Hot Flushes
12. Clinical safety of isoflavone-containing preparations
13. Clinical effects of isoflavones against menopausal hot flushes
References
Tempfer CB (2009). Side effects of phytoestrogens - a meta-analysis of randomized trials. Symposium on Evaluating the Efficacy and Safety of Isoflavones for Postmenopausal Women, 13-14 May. Milan (Italy): Council for Responsible Nutrition.
Safety 