After years of confusion surrounding the use of soy food consumption and breast cancer survivors, a large new study has found that eating soy foods does not increase the risk of breast cancer recurrence or death in breast cancer survivors.
The controversy has come about because soy contains isoflavones which are known to bind to oestrogen receptors in cells and have both pro-oestrogen and anti-oestrogen effects. Tamoxifen a well established drug in the treatment of breast cancer also binds to these oestrogen receptors so there was concern that the intake of soy would block this drug effect.
The study included pooled data from 9,515 breast cancer patients with an average follow up time of 7.4 years (the intake assessment was done at 14.6 months post treatment).
The data also indicated that it may also be beneficial to include some soy food into a healthy diet although the improved survival data here did not reach statistical significance.
This can not be extrapolated to soy supplements as supplements may differ in both type and amount and were not included in this study.
Ref: S Nechuta et al Vanderbilt-Ingram Cancer Centre.