I haven't been overly worried about GM foods myself, but Mercola has educated me yet again. In 1998 the occurrence of allergic reactions to soybeans in the UK increased by 50%. GM soy products entered the US market late in 1996. The issue seems to be that they're putting genes from peanuts and other common allergens into soy.
But the interesting thing is that the genes can cross from the soy into bacteria---this article considers the possibility that the allergen genes are entering our normal stomach bacteria and causing long term effects such as irritable bowel syndrome.
So you could be having an allergic reaction to a food that you didn't even eat. That food could have become part of your natural gut flora.
Time to rev up our gardens. This is getting out of hand.