Not too long ago I was having lunch with a new acquaintance and he asked me what I did for a living. When I told him he wondered out loud if a lot of people start asking me questions when they find out about my chosen profession. When I replied in the affirmative, he sighed and stated that he didnt have that problem, as he was a mathematician, and apparently not as many people found prime numbers fascinating. Of course I get a lot of internet articles too, and someone asked me to chime in on this particular one: Dangers of Soy.
Of course, one of the things we all need to think about when reading something on the internet is the quality of the source. Skeptoid and a few other skeptical bloggers have compiled this particular website which is a good place to start (Top Ten Worst Anti-Science Websites), but you might need to do a little bit more digging. Another physician friend of mine beat me to it and started digging around on this particular website only to find a lot of other anti-science misinformation regarding vaccines, etc. That is usually enough to make me want to ignore the information right there, as I would rather not give too much traffic to websites that are anti-science.
The other thing you need to do is examine how the information is presented. One red flag that immediately jumped out at me was the phrase independent research. Often this means that the reasearch was not accepted for peer review, meaning that there was no outside verification. I did follow the links in this article and found that there was a lot of information on animal studies, but you cannot directly apply this information to humans. We have peer review for a reason--not to stop people from coming up with ideas but to keep certain ideas from being taken too far. And the physiology of humans is different than that of rats, chickens, felines, etc., so we really cannot make health decisions based on animal studies.
And just like human physiology differs from other animals, we are also different than, well, plants as well. That might seem kind of obvious to many of us, but when people start tossing around phrases like estrogen like compounds it seems that people start thinking that isoflavones and estradiol concentrations as the same thing. So we they talk about the isoflavone level of the plasma concentrations of formula fed infants vs. others---they are comparing isoflavone levels only, not actual levels of human estradiol. That is like comparing the levels of iron to the levels of B12 in the blood stream--you are looking at components of cells in the blood but they are not the same thing. We also have to keep in mind that when isoflavones do bond to estrogens in the human body it is a pretty weak bond.
The rest of the article contains a lot of other statements that are made to sound scary but we do not have the evidence to support them. I could find some studies where they talked about soy being of concern in thyroid function because of animal studies, but it was just that, of concern. We do not have enough information to start making doomsday proclamations.
All that said, we do have to consider what I like to call the culture of eating in the United States where we have trouble with overconsumption. The author was right in that in cultures where soy is consumed it is usually done in MUCH smaller amounts and in different forms. So, if a person consumes soy sausage for breakfast, soy milk in the coffee (a lot of coffee), then has soy yogurt for a snack, then has a soy burger at lunch, then has edamame for a snack (like the whole bag), then soybean oil on their vegetables in the evening, followed up by some soy ice cream for dessert they MIGHT be getting a lot more isoflavones, phystic acid, and trypsin inhibitors than the human body has historically been able to handle. (And probably a few more pro-inflammatory omega-6 fats) For those that do sometimes throw in a little miso soup/natto sometimes, or eat a handful of edamame (and they maybe do not even do that everyday), there really is not enough evidence to make you give that up. For those of us who are not able to consume dairy and have been using soy cheese/milk/yogurt, etc whenever you need to have some kind of dairy-like goodness, you can rejoice because there are soy free options available for those things too.
And always keep in mind this phrase from our friend Paraclesus:
"All things are poison, and nothing is without poison; only the dose permits something not to be poisonous."
Take home message--overconsumption of soy is probably not a good idea, but then neither is overconsumption of anything. If you are not sure of where the soy might have crept into your diet, or you know that you have been consuming soy at every meal, it is time to start doing more label reading and time to get way more variety in your diet.