Do you have more information on Dr Zava and his research in this area? Also, do the findings apply to prostate as well as breast cancer? We imagine that many breast and prostate cancer sufferers use supplements that contain genistein. - Diane Townson, Chichester

WDDTY replies: David Zava, PhD, is a biochemist and research scientist who has worked and published extensively on the effect of oestrogens (natural and plant oestrogens, and xenoestrogen pollutants) for 25 years. He has co-authored some 60 scientific publications, including (with the late John Lee) the excellently titled What Your Doctor May Not Tell You About Breast Cancer.