What is the maximum amount of soy that one can eat without problems? Are there studies that have confirmed a threshold dose in relation to phytoestrogens, phytates, other things? Whether soy is bad or not is not the question, but mainly the quantity.
I got into a discussion with a vegetarian who has vegan leanings, and wishes to eat a meat-free diet. She's not adverse to eating eggs (I think), but she is supplementing their diet with some tofu (maybe 250-500g a week, not a lot, but some) and soy milk (they claim a liter a month or so). I've convinced her that there are bad things in soy, but she wants to know the dose at which problems occur. Essentially, she wants to continue eating soy, and wants to know how much she can eat without the undesired effects to mineral nutrition and her endocrine system. Since she's a fellow scientist, she wants to see some studies, which I am at a loss to provide.
It's clear to me not to eat any soy, but that fact of the matter is, that she wants to see a study with a convincing case that a certain amount is the maximum amount that one can eat without negative effects. So far I'm just going to try to make the case that there's so much potential for harm, that the best case of action is not to eat any, but any studies showing this would make it a lot easier. It doesn't help that all the studies I can find exposing the negative effects of soy are when it's a regular, or large, part of the diet.