I read a study about high-fructose corn syrup today, after being amazed by another article I read about how they make the stuff. (The Wikipedia entry has a lot to say too.)
Here’s the kicker: at least some HFCS has a higher mercury concentration (0.56 ppm) than most* fish you eat. So, if you’re someone who shouldn’t be ingesting much mercury, HFCS is probably a bad idea too. Don’t take my word for it, though, read the study.
There are two processes for producing HFCS, and one of them generally leads to undetectable levels of mercury, but unfortunately, you can’t find out what you’re getting just by reading the ingredients list. And while 0.56ppm is the worst sample they found, again, you can’t tell you’re not getting that level too.
Contrast that to fish: most people watching their mercury intake know which kinds of fish to avoid and which are safe. There are recommendations on how often you should eat which kinds of fish. With HFCS-containing products (which, by the way, is soooooo many things), it’s simply a blind guess.
It wasn’t immediately obvious that the FDA regulates mercury levels in HFCS, although it looks to me like they didn’t even know about it until this study.
So, the bottom line is that if you’re on a mercury-restricted diet, you should at least think about this issue.
[*Details: the study detected a concentration of 28µg mercury per 50g HFCS (or, 0.56 ppm) in the worst sample. Compare to the FDA's list of mercury levels in fish.]