http://www.eurekalert.org/pub_relea...e-cis011006.php

Genistein, a major component of soy, was found to disrupt the development of the ovaries in newborn female mice that were given the product. This study adds to a growing body of literature demonstrating the potentially adverse consequences of genistein on the reproductive system. "Although we are not entirely certain about how these animal studies on genistein translate to the human population, there is some reason to be cautious," said Dr. David A. Schwartz, Director of the National Institute of Environmental Health Sciences (NIEHS). "More clinical studies are needed to determine how exposure during critical windows of development can impact human health."

Genistein is the primary naturally occurring estrogen in plants (called phytoestrogens) and can mimic the effects of estrogen in the body. Genistein can be found in foods containing soy such as soy-based infant formulas as well as over-the-counter dietary supplements.

The results of this study conducted by researchers at the National Institute of Environmental Health Sciences (NIEHS), part of the National Institutes of Health, in collaboration with an investigator at Syracuse University, are published in the January issue of Biology of Reproduction.

The NIEHS researchers previously showed that mice given genistein immediately after birth had irregular menstrual cycles, problems with ovulation, and problems with fertility as they reached adulthood. The new study looks at the direct effects of genistein on the ovaries during early development.

"We knew genistein was linked to reproductive problems later in life, but we wanted to find out when the damage occurs," said Retha R. Newbold, MS, a developmental endocrinologist at NIEHS and an author on the study. "The study showed that genistein caused alterations to the ovaries during early development, which is partly responsible for the reproductive problems found in adult mice."

Female mice were injected with three different doses of genistein during their first five days of life. The genistein given to the mice was comparable to what human infants might receive in a soy-based formula, which is approximately 6-9 mg/kg per day. The researchers examined the effects on days 2 through 6.

The researchers found effects at all levels. Mice treated with the high dose (Gen 50 mg/kg) were infertile and mice treated with lower doses were subfertile, meaning they had fewer pups in each litter, and fewer pregnancies. Mice receiving the highest level of genistein, 50 mg/kg per day, had a high percentage of egg cells that remain in clusters, unable to separate and therefore develop abnormally. The researchers explain that oocytes that remain in clusters are less likely to become fertilized based on previous research. The largest difference between the genistein treated and normal mice was found at six days of age where 57 percent of the egg cells in the non-treated ovaries were single or unclustered; and only 36 percent in the genistein treated group were single

We think genistein inhibits the oocytes or egg cells from separating apart," said Wendy Jefferson, Ph.D. of NIEHS and lead researcher on the paper. "Since there are many egg cells in the same follicle instead of just one, the resources from the surrounding cells are spread too thin and they can't get the support they need to become a mature functioning egg cell."

"You need at least one good healthy single oocyte that is ovulated and fertilized by a sperm to get a healthy baby. Genistein seems to have a way of making this task very difficult," said Newbold.

"I don't think we can dismiss the possibility that these phytoestrogens are having an effect on the human population," said Dr. Jefferson. "They may not show their effects or be detected until later in life, but chances are they are having an effect."

Wendy Jefferson, Ph.D. of NIEHS and lead researcher on the paper seems to agree:



So, like, what will you do, Drs. Schwartz and Jefferson? Ban the use of all soy products in pregnant women, and soy formula in infants? Begin a massive advertising campaign warning women to avoid soy while they are pregnant? Call the CEO of Conagra in front of a Congressional subcommittee for tough questioning, and determine how many US Senators accepted contributions from major food corporations?


Oh, I see.

Well, I think scientists should stick to science, not litigation. We need 'em doing studies like this.
Don't forget that mouse studies don't tell the full tale for humans. Plus, do bear in mind that the mice were injected directly with truly vast doses of genistein, not fed it, and that could make a difference. And, the study got published in a journal so that it will be peer-reviewed for potential mistakes, and hopefully someone else will design a similar experiment and reproduce the results.
It would be great if we had more experiments so we could establish daily upper limits of unfermented soy. But since we don't do risky clinical trials on pregnant women, if the science holds up, there should definitely be some warning given to pregnant women (particularly vegetarian ones, who may consume more soy) about soy intake.

A search tells me that soy protein isolate is what is used in soy baby formula - doing some more searches, I think it depends on the processing whether the isoflavones or lignans are retained. Reading this, I hope they are not!
I guess you can buy soy formula anywhere - I haven't really looked - but all the baby-feeding advice I've read so far has said to ask your doctor what kind, and to try the milk-based formula first. And they all say breastfeeding is best, of course. Still, sometimes there are problems with nursing, and sometimes babies don't tolerate milk proteins well, and so some end up on soy formula. I think there are some other formulas, but I'm not sure what they are made of. If I have trouble breastfeeding, you can bet I'll try to avoid soy. Although the kid should tolerate milk just fine, if he's anything like his parents.

I'm glad to see this study getting attention - I think soy has been way oversold as "healthy." There's this idea that Asians eat buckets of it, but they really don't, and what they do eat is usually fermented forms of it (like tofu and miso) which aren't as high in the isoflavones that have the phytoestrogens.

If you look at soy milk in the grocery store it tends to have something on the carton saying "Look! I've got loads of isoflavones!" I learned years ago to avoid that, because I have thyroid disease, and soy isoflavones are goitrogenic. When I started weightlifting and drinking protein shakes, I was worried about which soy protein isolates might have isoflavones, and it was hard to tell (so I went with whey protein). I gave up eating those handy protein bars because I was worried about the soy protein in them. So I've been wary already for my own reasons.

Incidentally, soy is not the only food with phytoestrogens. It's hard to find a list that shows how much they contain, but lists of foods that do have them include flax, pumpkin seeds, and broccoli. But really, I think these foods are safe to eat. I think fermented soy products are safe to eat (tofu, miso, soy sauce, tempeh), and soybean oil should be safe too as the proteins are filtered out. But soy milk, and soy flour, and certainly some soy protein products are going to have these substances.

Tofu isn't usually fermented.



from http://www.nasoya.com/nasoya/productFAQ.html

Oh, okay!

Well, it still typically doesn't have the full slap of isoflavones. I guess it's when the 'whey' drains off, most of them must go with the liquid?
I think it has some, just not enough to be a problem.

I wonder if natto has a lot of isoflavones? It's fermented, but it is the whole beans. Does anybody eat enough of that for it to matter?

Of course, that still doesn't explain why anyone would want to eat the stuff.

There apparently is a fermented type of tofu called "chaw-tofu" which means "stinky bean curd". Yum - sign me up.

This would explain the feminisation of modern men (and gender switching in fish when it reaches the water), low sperm count in the western world and the propensity of 'confused' sexuality in the modern era of 'healthy' alternative eating of soy products and feeding of soya products to developing children. More research may be needed but it indeed explains a lot.

Exactly why the "men's" alternative doctors tell men to NEVER EAT SOY. There are a lot of other reasons why estrogen levels are way up in men and tesosterone levels down. Big Problem -- most regular doctors refuse to admit it.

if they're aware of it.