Anahad O’Connor, writing for the New York Times:
As far as any downside, most of the health concerns about soy stem from its concentration of phytoestrogens, a group of natural compounds that resemble estrogen chemically. Some experts have questioned whether soy might lower testosterone levels in men and cause problems for women who have estrogen-sensitive breast cancers. Animal studies have found, for example, that large doses of phytoestrogens can fuel the growth of tumors.
Fascinating. Are all these interactions well-understood? I seem to recall much of the debate around the new soylent meal replacement stuff could be boiled down to the question of how well we understand the effects of diet on the human body.