Wheat, barley, and rye are the three grains noted to contain gluten. There is an extensive list of grains and products the Celiac Disease Foundation site. Ten years after diagnosis I continue to find gluten in unexpected places. Below is a starter list to give you insight into some unlikely foods that contain gluten.
Alcoholic Beverages: More alcohols are distilled from grains than not. A few gluten free options are wine, unflavored rum, some tequilas (where the only ingredient is agave), and some potato vodkas. I find the workers at my local liquor store are very helpful when I ask about gluten free options.
Barley Malt or Malt: Anything containing either of these ingredients will not be gluten free.
Blue Cheese: Cheese is naturally gluten free but the blue mold strains in blue cheese are commonly started by coating cheese with flour. So Gorgonzola and blue cheese are to be avoided unless you have specific knowledge that the particular brand is gluten free.
Beer: Unless it is a special gluten free beer, then the beer contains gluten, a lot of gluten.
Bottled Salad Dressing: The ingredient list on a bottle of dressing can be long and undecipherable, so it is best to look for one labeled gluten free.
Chocolate: Gluten seems to make its way into chocolate products frequently during processing; gluten is not naturally in chocolate. Checking the website of your favorite brand, and/or sending them an email if there is no “Allergens” page listing which of their products are safe is the most expedient way to find which brands/products are gluten free. Some chocolate chip makers are now listing gluten free on their packages, but most require a little research.
Corn Bread Mix: If it does not say gluten free on the label of corn bread mix or cornmeal, then it most likely contains gluten. The gluten can enter when the corn is being processed or packaged on machines also used for wheat products or the corn has been stored in silos that are also used for storing grains containing gluten. Either of these conditions will mix in enough gluten to create difficulties for your guest with Celiac, so look for cornmeal with a label that says gluten free.
Dairy: Diary is generally considered gluten free but look out for the common stabilizer “mono and diglycerides” on the label. This stabilizer often formulated to include grains. Half and half, heavy cream, and ice-cream are where I have found this stabilizer. If the dairy product contains “mono and diglycerides” it may be safe, or it may not, look for a gluten free label on the package if this stabilizer is included on the ingredient list. Generally organic dairy products are gluten free and all cartons of milk (in my experience) are gluten free.
Deli Meat: Deli meats are processed meats that often include grains with gluten. There are brands that have gluten free items such as Boar’s Head and Applegate, but not all deli meat is gluten free so verify that what you are planning on purchasing is gluten free. See Cross-contamination page for further suggestions on purchasing deli products.
Flavored Seltzer Water: Those natural flavorings are sometimes made from wheat, and can contain enough gluten to made a Celiac not well.
Modified food starch: This is a starch made from an unspecified grain and that grain likely contains gluten, so any product with modified starch on its label needs to be avoided. Corn starch is gluten free.
Mustard: Read the ingredient label and avoid unspecified “vinegar”. Look for a mustard that is made with wine vinegar or cider vinegar or find a mustard with a gluten free mark on the label.
Nuts: Not because there is gluten naturally in nuts but because they are packaged on the same machines used to package pretzels and are not thoroughly cleaned between processing different foods. Cocktail nuts sometimes have flour listed on the ingredient label; I can only guess why a company adds flour to their can of nuts. My finding has been that Trader Joe’s roasted and raw nuts are generally gluten free. On the other hand, Whole Foods’ nuts and other foods sold in the round plastic containers near the nuts have been contaminated with gluten (this includes the raisins).
Oatmeal: Many with folks with Celiac cannot tolerate any oats (even those labeled gluten free), some can tolerate a little bit of oats, and some have no apparent reaction to oats. Please inform your dinner guest if you include oats in a dish and so your guest can make informed decisions on what is safe for them to eat.
Parmesan cheese that is already grated: It is not the cheese that has gluten but the fillers that are included with the pre-grated cheese often contain gluten. Tip: consider buying a wedge of Parmesan and grating it yourself.
Soups and Stocks: Flour is often used as a thickener in stocks and soups. Please use only soups and stocks that are specifically labeled gluten free. Tip: the brands that label their products gluten free seem to be packaged in boxes more often than in cans, hopefully this will save you time in your search at the grocery store.
Soy Sauce: Many common brands of soy sauce are fermented from wheat. Look in the specialty or organic section of the store and you will likely find a bottle that is made from soy and is gluten free. Soy is gluten free unless cross-contaminated in processing.
Vinegar: Specifically balsamic vinegar and distilled white vinegar can contain gluten. Balsamic vinegar sometimes includes caramel coloring made from wheat (especially less expensive varieties) so read the label and avoid anything with caramel coloring. Distilled white vinegar is often distilled from grains that contain gluten (wheat, rye, and barley), and although some argue that the distilling process destroys the gluten, it is still there but the particles have been broken down so that they are harder to detect. White vinegar distilled from corn and other gluten free ingredients are available, just read the label. When I cannot find a gluten free white vinegar I use a white wine vinegar as a substitute.