At present it is still not clear if eating a diet high
in phyto-oestrogens (soy products) is safe for women who have, or have had, breast cancer. For women with oestrogen receptor positive breast cancer who are
taking an aromatase inhibitor such as anastrozole, it is still unclear whether eating soy foods or taking
soy supplements will block or enhance the actions of the aromatase inhibitors. Results
of scientific studies are contradictory, with some studies showing that dietary soy can interfere with the actions of aromatase inhibitors and other studies showing that soy can possibly enhance aromatase inhibitors, such as anastrozole.
As Cancer Council NSW advises, moderate consumption of soy
foods, as part of an overall healthy eating plan, is unlikely to have
any harmful effects. In the US, the positions of the American Cancer Society and the American Institute for
Cancer Research
are similar: that soyfoods can be safely consumed in moderation by women with breast cancer. It is best however to avoid high doses of soy products, such as soy supplement tablets or powders.
