I will tell you the same thing I told her:
"Gluten"' is a protein found in various grains. It is made up of glutenin and gliadin and, simply put, is what makes dough stretch. If you've ever seen someone throwing pizza dough over their heads you are really seeing gluten stretch out the dough.
A gluten-free diet requires someone (usually someone with celiac disease but people follow the gluten-free diet for other reasons, too) to completely avoid any gluten-containing grains or ingredients derived from gluten grains.
Common grains containing gluten:
- Wheat
- Rye
- Barley
- Triticale
- Malt (Sometimes listed as "Malt Syrup" or "Barley Malt")
- Durum Wheat
- Graham
- Kamut
- Semolina
- Spelt
Label reading is the first step when trying to determine if a food is gluten-free. Obviously, if it clearly lists any of the above grains, it is not gluten-free. However, gluten can "hide" in ingredients. While this is getting better, hidden gluten is still an issue. Your best bet is to always contain manufacturers when attempting to determine if a food is gluten-free.
A great source of information on what is gluten-free (and what is not) is the Gluten Intolerance Group (GIG). Here is a link to their very helpful flier of the ins and outs of the gluten-free diet!