* The increased level of estrogen can manipulate the menstrual cycle in women.
* soybeans are high in phytic acid, which, in large amounts, can block the uptake of essential minerals like calcium, magnesium, copper, iron and especially zinc in the intestinal tract.
* When manufacturers of soy protein isolates and supplements recommend that people consume 100 grams of soy protein a day (the equivalent of 7 or 8 soyburgers), they are ignoring the unknown effects of overdosing on [[isoflavones]] is still unknown. I believe it's probably safer, until more is learned, to avoid concentrated soy supplements entirely.
* contains enzyme inhibitors, which hinder protein digestion and haemagluttin, which causes red blood cells to clump together and inhibits oxygen take-up and growth.