>Claire Bloodgood posted:
>In going over my Google search results
>("male infants" + soy + phytoestrogens), it seems there is a lot more
>controversy on the subject than I would have expected.

It's hugely controversial, especially when soy formula is brought into the 
picture. During the course of writing articles on the topic for 
Environmental Health Perspectives, I've spoken with researchers on both 
sides of the issue. They're all very nice people, but they just do NOT agree.

I'm not well-versed on potential prenatal effects of phytoestrogens, but I 
recalled reading a bit about phytoestrogens in breastmilk. Searching my 
files, I came up with the following from KDR Setchell et al. (The Lancet, 5 
July 1997, 350: 23-27). On page 26, they write:

"Our data do not support claims about human milk as a source of 
phyto-oestrogens. Mean total plasma isoflavone concentration of 
breast-milk-fed infants was 4.7 (1.3) ng/mL, which is less than 1/200th the 
level attained by feeding on soy-based formula. Isoflavone concentrations 
of human breast-milk are also very low (5-15 ng/mL) and although they can 
increase up to 10-fold when the lactating mother consumes soy foods, the 
daily intake by the infant of phyto-oestrogens from human milk is only 
0.005-0.01 mg. Our data therefore provide little reason for concern about 
phyto-oestrogens from human breast-milk, even when mothers consume soy 
during lactation. Because of the weak oestrogenic activity of isoflavones 
(10^-2 to 10^-3 that of oestradiol), the dietary intake of phyto-oestrogens 
from human milk is unlikely to exert biological effects."

As one might imagine, there's not a huge amount of research with regard to 
phytoestrogens in breastmilk. Dr. Setchell has a few other studies with 
data on the topic (e.g., American Journal of Clinical Nutrition, 1998, 
68[suppl]: 1453S-1461S); a few other researchers have looked at it as well 
(e.g., A.A. Franke, J.L. Slavin). Most of what's out there with regard to 
phytoestrogens and infant diet focuses on the intake from soy formula. As 
explained above, that intake dwarfs the amount that might be in breastmilk.

Setchell estimates that a 4-month-old infant on soy formula takes in about 
28-47 mg of isoflavones per day, with genistein being the most abundant. 
Other research indicates that this level of phytoestrogens is sufficient to 
affect the length of a woman's cycle. However, there's no human data to 
suggest effects on human infants. But, there's no proof that none exist.

This is where the controversy really starts spiralling upward.

At any rate, since soy formula represents the largest infant exposures to 
phytoestrogens, that's where the research emphasis is placed. There are 
several on-going research studies such as the Study of Estrogen Activity on 
Development (SEAD) <http://www.codares.com/sead/> and work being done by 
Thomas Badger at the Arkansas Children's Nutrition Center in Little Rock, 
AR (described in Agricultural Research, January 2004, p. 8-10).

regards,
Julia

Julia R. Barrett
Freelance Science Writer & Editor
Mom to Sean (5) and Kira (21 months)
Madison, Wisconsin

             ***********************************************

To temporarily stop your subscription: set lactnet nomail
To start it again: set lactnet mail (or digest)
To unsubscribe: unsubscribe lactnet
All commands go to [log in to unmask]

The LACTNET mailing list is powered by L-Soft's renowned
LISTSERV(R) list management software together with L-Soft's LSMTP(R)
mailer for lightning fast mail delivery. For more information, go to:
http://www.lsoft.com/LISTSERV-powered.html