Some populations can handle soy better due to their genetics. The same thing happens with Asians, specifically Japanese, being able to handle high amounts of iodine due to the amount of seaweed and seafood they've eaten through the centuries.
This is also why White populations can typically digest milk and dairy products better than others because we had a culture that consumed much more dairy for centuries.
Soy and soybeans are not fit for human consumption anyway.
Soy is poison.
Soison.
EDIT: Apparently, modern soy sauce does not actually have any soy in it. Weird.
The Asians seem to be doing OK though.
Some populations can handle soy better due to their genetics. The same thing happens with Asians, specifically Japanese, being able to handle high amounts of iodine due to the amount of seaweed and seafood they've eaten through the centuries.
This is also why White populations can typically digest milk and dairy products better than others because we had a culture that consumed much more dairy for centuries.