They probably don't drink Silk. I spoke to the Chinese girl at our local Chinese Restaurant. She advised that they drink soy milk every a.m. for breakfast, like Americans drink cow's milk. They also eat a lot of "bean curd".
I recently won a SoyToy soy milk maker whose design origin is from Korea. It is a very easy way to make fresh soy milk without all of the commercial stuff added to it. I still am not sure how this will affect thyroid conditions, but I will be finding out.