This is my rule when I go grocery shopping: if it has a long list of ingredients (more than five), and I recongize an ingredient as being made in a lab, I avoid it. Anything that sounds manmade and is most likely bad for you.

A perfect example is MSG: did you know there are at least 26 names for MSG? Marketers hide the ingredients by changing the names to confuse consumers. It is better just to avoid unidentifiable ingredients altogether.