One of the things going gluten free has taught me is to ALWAYS check labels. This can be extremely difficult if you don't educate yourself on what ingredients are on the foods to avoid list. Here are several links and articles that may help you discover what to look for when shopping. I try to eat as natural and organic as possible, so these sources talk about more than just gluten. Here a few rules to follow to help you eat safely.
Rule #1: Never eat anything without reading the label first.
Rule #2: Consistently check labels, even of your favorite products, as product formulations can change.
Rule #3: If you are unsure of an ingredient, or the company's policy on labeling, call the phone number on the back of the product or email the company.
I hope these links help you to shop smarter and safer.