http://pubs.niaaa.nih.gov/publications/arh22-3/220.pdf

What an interesting study! Seems that alcoholic beverages provide a meaningful boost in feminization as they contain significant amounts of biologically active phytoestrogens (the key being "actve").

The detail is worth the read. I think it also raises an additional question: Given that so many transsexuals report drinking heavily (often described as a coping behavior), I wonder if there is a biological driver.