It's a pretty simple answer: fermented soy is the soy you want to eat and non-fermented soy is the soy you probably are eating already. The United States produces non-fermented soy in large quantities because it's easier to grow in alternation with corn crops. Soy contains naturally toxins that are, you guessed it, bad for you, and the fermenting process is what removes them. It's pretty hard to avoid non-fermented soy. It's in practically everything, usually as soy lecithin. A little bit isn't going to hurt you but if you're eating tons of it--just like if you eat tons of anything--you're on the riskier side. There are arguments saying that any kind of soy, including soy lecithin, is healthy and good for your cholestoral and so you have to decide which argument you believe. However, fermented soy is generally undisputed as healthier and you're probably better off eating it--instead of non-fermented soy--whenever possible.