What is the recent controversy concerning high fructose corn syrup, obesity and diabetes? Is it true that it contains high levels of mercury?
Why are labels on few products marked as "does not contain high fructose corn syrup," such as bread, ketchup etc. Is this sweetener harmful to health?
I have not heard the mercury issue as it relates to high fructose corn syrup (although you hear a lot about mercury levels in fish and shellfish). The corn industry in the United States is such a powerful lobby with the federal government, that it has become more difficult to limit or regulate the use of HFCS, even when public health is at stake. Researchers at a number of medical institutions have found a link between consumption of HFCS and obesity, which now afflicts almost 1/5 of the entire US population.
Some have suggested the high "sweetness" of HFCS is contributing to Americans craving for similar amounts of sweet, which outside of HFCS and artificial sweeteners, requires a great deal of sugar. So if you are used to HFCS sweet, for example, a teaspoon of sugar in your tea won't sweeten it to what you are used to, so we tend to use more, and buy products with higher sugar content. It's not an addicition, but it acts the same way in a lot of behaviors.
UPDATE: Did a little background research and found a Web MD story from January of 2009 that suggests mercury was at "detectable" levels in 17 foods that use HFCS, out of 55 tested. More at the link below.
I have not heard the "mercury" theory concerning high fructose corn syrup. Actually, the health-issues related to high fructose corn syrup have to do with the sweetener's form. HFCS changes the sugar in cornstarch (glucose) to fructose. The reason for doing this is to extend the shelf life of the foods containing HFCS. It is a cheap preservative.
Think about it. If it extends the shelf life of all these foods, imagine what these foods do inside your body. If they last longer outside the body, they last longer inside the body. HFCS is harder for our digestive systems to break down than regular sugar. This is why it has been related to obesity and diabetes (and the myriad of health problems directly connected to those two). If you are interested in the subject you should read any of Michael Pollan's books.