A few thoughts: What about all the kids (pre filling age) who have conditions and ailments that can be associated with allergies/food intolerances and have had no mercury fillings. I am not promoting amagram fillings. I went so far as to have all mine removed a few years ago. At the time I thought it was the causatory factor with my food intolerances. It was not the dramatic cure I hoped for but my teeth and gums have been remarkably healthy ever since!
I believe that mercury is yet another "factor" in our environment that aggravates the poor "condition" that we all seem to find ourselves in but I don't think it is the cause.
Ten years ago I gave up all dairy products (later on I gave up other things). At the time I didn't really know too much about candida or parasites. After a few weeks of very severe reaction (flu, swollen glands, bloodshot eyes etc). I suddenly felt amazing. The suprising change was of "mood". I would never have gone to a doctor for depression but I suddenly felt light and happy! I suddenly realised I could relate moods like anger, fear, sadness to the food that I was eating. If I stuck to the diet I felt GREAT. The problem was that if I strayed from the path I felt TERRIBLE. The consolation was that I was IN CONTROL of my health (that has to be the best situation).
I thought there was something wrong with food. I turned organic (I even tried to set up an organic small-holding). There are some foods that I react to particularly if they are non-organic like apples and chicken (the juices used to affect me from non-organic) but these are AGGRAVATIONS and not the cause.
I am beginning to agree with a lot of people that it looks like Candida and Parasites could be the causatory factor we are all looking for.