What Is Gluten?

By Trisha Howell, MSH, RD, LD/N, IFMCP

With all the talk about gluten-free diets these days, you may be wondering: What is gluten? Which grains contain it, and can avoiding gluten be healthier?

Gluten is a protein found in wheat, rye, barley, and triticale. Gluten is activated when flour is moistened and kneaded or mixed and contributes to the chewy, elastic consistency associated with bread and other baked goods. It is also added as a food additive or thickener.1

Gluten-containing grains and hidden sources2

Wheat: bulgur, couscous, cracked wheat, durum, einkorn, emmer, faro, farina, graham, hydrolyzed wheat starch, kamut, matzoh, orzo, seitan, semolina, spelt, wheat bran, wheat germ, wheat grass, wheat starch, wheat berries, whole wheat including sprouts made from the above grains

Rye: all forms of rye including whole rye, rye flour, pumpernickel, and any sprouts made from rye

Barley: all forms including barley malt in beverages, flavoring, extract, syrup, vinegar, and any sprouts made from barley; it is easy to miss barley malt as a gluten-containing ingredient when it is listed as malt or used as a flavoring

Oats: the naturally occurring proteins in oats are similar to gluten and can provoke a similar reaction for some individuals if not specifically indicated on the label as “gluten-free” due to cross-contamination with other gluten-containing grains due to processing, packaging, and transporting2

Triticale: newer grain grown similar to quality of wheat yet more tolerant to growing conditions of rye; it is found in breads, cereals, and pasta

Foods That Could Contain Gluten3 Gluten-Containing Ingredients
Ales/lagers/beer Baking powder
Brewer’s yeast Barley grass
Broth/bullion Brewer’s yeast
Candy/licorice Brown rice syrup
Citric acid Caramel color
Communion wafer Dextrins (deli meat/poultry)
Condiments Grain alcohol
Croutons Gravy cubes
Dates (rolled in oat flour) Ground spices
Gravies Malt/maltose
“Flavored” nuts Natural flavoring
Flavored teas and coffee Seasonings (spice blends)
Food starch Self-basting poultry
Imitation seafood Soy sauce
Imitation bacon
Nondairy creamer
Processed meats
Soba noodles
Soup stock
Some supplements—check labels

Foods that are gluten-free3

There are many natural sources of gluten-free, whole foods abundant in the diet. They include colorful fruits and vegetables, animal proteins (beef, chicken, fish, pork, and turkey), dairy, beans, nuts, and seeds.

Nongluten grains: Amaranth, buckwheat groats, buckwheat noodles, chia, farro, gluten-free oats, kamut, millet, rice (basmati and brown), sorghum, teff, stone-ground corn, and quinoa

Can going gluten-free improve health?

There is growing evidence that gluten sensitivities are associated with adverse health conditions.4 Additionally, some people experience milder symptoms such as abdominal discomfort, bloating, indigestion, or no symptoms at all.4

If gluten-containing foods are continually consumed, even in small doses over time, it can actually lead to nutrient deficiencies due to malabsorption.4,5 Some individuals may experience immune reactions to gluten, triggering immune dysfunction and oxidative stress.4,5 According to the Food and Drug Administration (FDA), gluten-free is determined by < 20 parts per million (ppm).Elimination of gluten relieves the symptoms and often reverses the issues associated with consuming gluten.4,5

Removing gluten from the diet

A lifestyle medicine approach can support improved health by focusing on whole foods, instead of relying on gluten-free convenience foods. Base your diet around naturally gluten-free foods (see list above).

Shopping and eating out

The key is to read labels and menus, looking specifically at the ingredient section for wheat, rye, barley, oats, and triticale, which indicates that those foods contain gluten. Also, both at home or a restaurant, the gluten-free items need to be stored away from gluten-containing items so there is no cross-contamination. Here are some helpful guidelines to follow:

  1. Read the food label to look for gluten-containing ingredients.
  2. Look for gluten-free (GF) symbol on packages.
  3. Enquire with the restaurant if it has gluten-free (GF) options if not noted on the menu.
  4. Ask how the food is prepared when eating at both restaurants and/or social gatherings. Inquire if foods have been dusted with flour or used kitchen equipment that may have been cross-contaminated such as toasters and deep fryers.

This is the first post in a new series on gluten. To learn more about gluten-free grains (including preparation ideas!), stay tuned.

Get more tips on going gluten-free and more in the Metagenics blog.


  1. Biesiekierski JR. What is gluten? Journal of Gastroenterology and Hepatology. 2017; 32(1):78–81.
  2. Sources of gluten. Celiac Disease Foundation. https://celiac.org/gluten-free-living/what-is-gluten/sources-of-gluten/. Accessed January 25, 2019.
  3. Gluten-free foods. Celiac Disease Foundation. https://celiac.org/gluten-free-living/gluten-free-foods/. Accessed January 25, 2019.
  4. Catassi C et al. Non-celiac gluten sensitivity: the new frontier of gluten related disorders. Nutrients. 2013; 5:3839-3853.
  5. Aziz I et al. The rise and fall of gluten! Proceedings of the Nutrition Society. 2015);74:221–226.