I agree with my fellow posters; Mercury is most likely offgassing at an increased rate due do the abrasive action of chewing removing micro-corrosion on the surface of the fillings which helps slow down offgassing. Heat?which can be transferred to the fillings from hot food?also increases offgassing, often dramatically.

I had an employee with a few amalgam fillings that suffered from several mercury-related issues so I suggested she stop chewing gum. Her health improved so much within days that she was completely astounded.