Some time ago, I was asked this great question:
I had been planning to research and write a really detailed post, until I discovered that my Mother-in-Law had already written one!
The only major item that I would add to the list is:
This corn-based sweetener is used in a wide variety of baked goods, canned fruit, fruit juices, beverages, jams, gum and more. One main concern is that it's form of sugar is fructose, rather than glucose. Glucose is used by our bodies as an energy source, but fructose is is metabolized and stored as a fat more than any other sugar. Because HFCS does not stimulate insulin or leptin, which help to regulate blood sugar and signal to us that we are full and need to stop eating, it most likely contributes to overeating and weight gain.
It contains no nutrients in and of itself, so it is nothing but a drain on our bodies, which must use stored energy and nutrients to digest and assimilate it. As I mentioned, it is corn- based, and most corn is genetically-modified. As well, processed foods have gradually become more and more corn-based, increasing our intake of this sugary grain and leading to more unbalance in our diets that tend to be grain-sugar-carb heavy and lacking in vegetables and high quality protein.
Of course, the goal is to avoid as many preservatives as possible, not just the ones that we know for certain are dangerous. The easiest way to do that is to eat a simple, whole foods diet and avoiding packaged and processed foods (but you all know that already, don't you? :)