If you feel fine eating garlic, there is your answer. If you have health issues and notice any bad effect, wouldn't you want to be informed? Discernment is the key, as usual, knee jerk reaction does nothing but kick someone in the pants (if thats what you are after).
I mistakenly said garlic chelates mercury, and on its own, it does not, it MOBILIZES it, which if not excreted, just redistributes it, mainly to the liver and possibly more dangerously to the brain.
If you have brain fog, especially after eating garlic or sulphurous foods, you may be experiencing die-off as these foods ( esp. garlic) are anti-fungal and anti parasitic. If you have candida in the first place, this is the body's way of protecting your gut from heavy metals. and sadly, it is almost impossible to get rid of candida if you have amalgam fillings unless you stick rigourously and continuously to the awful no-fun diet . Your body will keep on doing what it deems best to protect you.
Large sea fish have large livers with a higher accumulated level of mercury, that is why tuna is particularly bad.
Heres some good very basic info on garlic/sulphur, amino acids, ....
http://tuberose.com/Sulphur_and_Mercury.html
I would say garlic and onions are quite inportant to buy organic.