This report talks about new introductions to the American diet. However, though soy may be relatively new to the US, my understanding is that Soy and soy-based products like Tofu have been popular in countries like China and Japan for many centuries.

Has any research been done to establish whether soy has been harmful in countries where they've been eating it for generations ?

I'd also be curious to know whether the alleged "harmful" effect observed in soy-based products (like soymilk etc.) has also been observed in plain soybeans.