Monosodium glutamate (MSG) is a commonly used "flavor enhancer," and so powerfully so that (arguably) you could spray it on roadkill and it would taste good. This omnipresent ingredient in modern mass market food takes advantage of our biologically hard-wired taste receptors, and makes it very hard to stop eating the foods "seasoned" with this ingredient.
Despite common perception, the toxic food additive MSG is everywhere - not just in Chinese food! This taste enhancer is actually hidden under dozens of ingredient names in all sorts of processed foods, restaurant foods, beverages, chewing gums, vitamins and supplements. It is added to foods in higher dosages than ever before, and more and more people are experiencing symptoms.