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).
Data from animal experimentation clearly speak against the hypothesis of the German BfR of isoflavones inducing an estrogen-analogous stimulation of breast cancer in postmenopausal women. This was also confirmed in the presentation by Dr. Eva Lundström of the Swedish Karolinska institute (Lundström 2009), who pointed to the epidemiological finding of a distinctly lower rate of breast cancer in countries with a high consumption of soy (Wu et al. 2008). The effect of the isoflavones on cell proliferation in the breast was examined in detail in at least four studies, in healthy women (Cheng et al. 2007; Hargreaves et al. 1999) as well as breast cancer patients (Palomares et al. 2004; Sartippour et al. 2004).
Cheng et al. (2007) administered 60 mg of isoflavones in a fruit drink to 26 postmenopausal women, with 25 women in the placebo control group. Safety was assessed by biopsies. The study duration was 12 weeks. Hargreaves et al. (1999) presented results from analyses of nipple aspirate fluid in 28 premenopausal women and 23 controls where the isoflavone group had been exposed to 45 mg of isoflavones daily for the duration of 2 weeks. Palomares et al. (2004) published results from a pilot study in 18 disease-free women previously diagnosed with breast cancer, 9 of which had been exposed to 100 mg of isoflavones daily for 12 months. Safety endpoints were biopsies, histology and estrogen receptor expression. Finally, Sartippour et al. (2004) examined women with invasive breast cancer scheduled for surgery. 17 women received a daily dose of 200 mg of isoflavones for an average of 23 days. The control group consisted of 26 women on placebo. Safety was assessed through biopsies and surgical specimes, with measurements of estrogen/progesterone receptor expression, and markers of apoptosis and mitosis. In no case the results pointed to a stimulation of cancer formation.
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
Lundström E (2009). Effects of isoflavones on in vivo breast cell proliferation in normal subjects and breast cancer patients. Symposium on Evaluating the Efficacy and Safety of Isoflavones for Postmenopausal Women, 13-14 May. Milan (Italy): Council for Responsible Nutrition.
Palomares MR, Hopper L, Lehman CD, Storer BE and Gralow JR (2004). Effect of phytoestrogens on menopausal symptoms in breast cancer survivors. Proc Soc Integrative Onc:75.
Safety 