The first thing I focused on was the ingredient that was most pervasive--corn syrup.
That's extremely unlikely. The most pervasive ingredient is high fructose corn syrup, not corn syrup (they are *extremely* different things.) Corn syrup (which is nearly impossible to find - even in bottles labeled "Corn Syrup") is 100% glucose, whereas HFCS is a solution of fructose and glucose (at least 42% fructose, usually 55%, but sometimes as much as 95% fructose.)
I now avoid it like the plague. Within a month of removing it from my diet (as much as possible, the shit is in everything), the heartburn stopped entirely.
You should check to see if it's a sensitivity to corn, or if it's the fructose. To test: go to a brewer's supply and buy a bottle of glucose (this is 100% corn syrup.) From a health food store, buy a jar of brown rice syrup (70% maltodextrin, 30% glucose). Try each one for a few days and see the result. If both cause heartburn, it's a sensitivity to glucose. If the corn syrup does but the rice syrup doesn't, it's a sensitivity to corn. If neither one does, it's probably a sensitivity to high fructose corn syrup.
The only logical conclusion I can come to, considering the stuff (corn syrup) has been in HEAVY use for decades now, is that the medical "industry" knows, but cannot monetize the solution--removing corn syrup from ones diet. Telling people to stop eating it would actually cut into their business. Corn syrup makes them money in the form of direct medical symptoms that need to be treated and the inherent medical problems associated with obesity. LOTS of money.
If this was true, how is it that the medical industry says to cut out saturated fat and sodium for other ailments?
The actual reason is much simpler: the research on high fructose corn syrup is just beginning, and there is a *lot* of effort from the corn industry to block or obscure it. For some interesting viewing (it's quite long, and relatively heavy on the biochem) you should watch this: http://www.youtube.com/watch?v=dBnniua6-oM