Gluten-free diet: What’s allowed, what’s not

Gluten-free diet: What’s allowed, what’s not

By Mayo Clinic Staff

A gluten-free diet is a diet that excludes the protein gluten. Gluten is found in grains such as wheat, barley, rye and triticale (a cross between wheat and rye).

A gluten-free diet is used to treat celiac disease. Gluten causes inflammation in the small intestines of people with celiac disease. Eating a gluten-free diet helps people with celiac disease control their signs and symptoms and prevent complications.

Initially, following a gluten-free diet may be frustrating. But with time, patience and creativity, you’ll find there are many foods that you already eat that are gluten-free and you will find substitutes for gluten-containing foods that you can enjoy.


The gluten-free diet is a treatment for celiac disease.

Diet details

Switching to a gluten-free diet is a big change and, like anything new, it takes some getting used to. You may initially feel deprived by the diet’s restrictions. However, try to stay positive and focus on all the foods you can eat. You may also be pleasantly surprised to realize how many gluten-free products, such as bread and pasta, are now available. Many specialty grocery stores sell gluten-free foods. If you can’t find them in your area, check with a celiac support group or go online.

If you’re just starting with a gluten-free diet, it’s a good idea to consult a dietitian who can answer your questions and offer advice about how to avoid gluten while still eating a healthy, balanced diet.

Allowed foods
Many healthy and delicious foods are naturally gluten-free:

  • Beans, seeds, nuts in their natural, unprocessed form
  • Fresh eggs
  • Fresh meats, fish and poultry (not breaded, batter-coated or marinated)
  • Fruits and vegetables
  • Most dairy products

It’s important to make sure that they are not processed or mixed with gluten-containing grains, additives or preservatives. Many grains and starches can be part of a gluten-free diet:

  • Amaranth
  • Arrowroot
  • Buckwheat
  • Corn and cornmeal
  • Flax
  • Gluten-free flours (rice, soy, corn, potato, bean)
  • Hominy (corn)
  • Millet
  • Quinoa
  • Rice
  • Sorghum
  • Soy
  • Tapioca
  • Teff

Always avoid
Avoid all food and drinks containing:

  • Barley (malt, malt flavoring and malt vinegar are usually made from barley)
  • Rye
  • Triticale (a cross between wheat and rye)
  • Wheat

Avoiding wheat can be challenging because wheat products go by numerous names. Consider the many types of wheat flour on supermarket shelves — bromated, enriched, phosphated, plain and self-rising. Here are other wheat products to avoid:

  • Bulgur
  • Durum flour
  • Farina
  • Graham flour
  • Kamut
  • Semolina
  • Spelt

Avoid unless labeled ‘gluten-free’
In general, avoid the following foods unless they’re labeled as gluten-free or made with corn, rice, soy or other gluten-free grain:

  • Beer
  • Breads
  • Cakes and pies
  • Candies
  • Cereals
  • Cookies and crackers
  • Croutons
  • French fries
  • Gravies
  • Imitation meat or seafood
  • Matzo
  • Pastas
  • Processed luncheon meats
  • Salad dressings
  • Sauces, including soy sauce
  • Seasoned rice mixes
  • Seasoned snack foods, such as potato and tortilla chips
  • Self-basting poultry
  • Soups and soup bases
  • Vegetables in sauce

Certain grains, such as oats, can be contaminated with wheat during growing and processing stages of production. For this reason, doctors and dietitians generally recommend avoiding oats unless they are specifically labeled gluten-free.

You should also be alert for other products that you eat or that could come in contact with your mouth that may contain gluten. These include:

  • Food additives, such as malt flavoring, modified food starch and others
  • Medications and vitamins that use gluten as a binding agent
  • Play dough

Watch for cross-contamination
Cross-contamination occurs when gluten-free foods come into contact with foods that contain gluten. It can happen during the manufacturing process, for example, if the same equipment is used to make a variety of products. Some food labels include a “may contain” statement if this is the case. But be aware that this type of statement is voluntary. You still need to check the actual ingredient list. If you’re not sure whether a food contains gluten, don’t buy it or check with the manufacturer first to ask what it contains.

Cross-contamination can also occur at home if foods are prepared on common surfaces or with utensils that weren’t thoroughly cleaned after being used to prepare gluten-containing foods. Using a common toaster for gluten-free bread and regular bread is a major source of contamination, for example. Consider what steps you need to take to prevent cross-contamination at home, school or work.


People with celiac disease who eat a gluten-free diet experience fewer symptoms and complications of the disease. People with celiac disease must eat a strictly gluten-free diet and must remain on the diet for the remainder of their lives.

In some severe cases, a gluten-free diet alone can’t stop the symptoms and complications of celiac disease. In these cases, doctors might prescribe medications to suppress the immune system.


Not getting enough vitamins
People who follow a gluten-free diet may have low levels of certain vitamins and nutrients in their diets. Many grains are enriched with vitamins. Avoiding grains with a gluten-free diet may mean eating fewer of these enriched products. Ask your dietitian to review your diet to see that you’re getting enough of these key nutrients:

  • Iron
  • Calcium
  • Fiber
  • Thiamin
  • Riboflavin
  • Niacin
  • Folate

Not sticking to the gluten-free diet
If you accidentally eat a product that contains gluten, you may experience abdominal pain and diarrhea. Some people experience no signs or symptoms after eating gluten, but this doesn’t mean it’s not damaging their small intestines. Even trace amounts of gluten in your diet may be damaging, whether or not they cause signs or symptoms.

What About Oatmeal?

Gluten proteins in wheat, barley and rye cause serious health problems for people who digest them poorly. Although oatmeal doesn’t naturally contain gluten, oats may be contaminated with it during growing, transportation and processing. Packaged oats produced through a gluten-free process are considered safe in moderation for most gluten-intolerant people, including those who suffer from the extremely negative response to gluten called celiac disease. However, some celiacs are adversely affected by avenin protein in oats.

Gluten Proteins

Gluten is a catch-all term for types of protein in wheat, barley and rye, as well as in hybrids of these grains, including kamut, spelt and triticale. These proteins cause a broad variety of problems when consumed by gluten-intolerant people. All contain closely related sequences of amino acids. Gliadin is the part of wheat that causes gluten sensitivity and celiac disease. In rye, secalin is the problem protein; in barley, it is hordein. To avoid contamination by these proteins, oats need to be raised on fields that are away from other grains and never used to grow gluten crops. They must be transported in gluten-free vehicles, stored in facilities that aren’t used for gluten grains and processed in gluten-free mills.

Gluten Intolerance

Gluten intolerance encompasses both celiac disease, which is sometimes called gluten-sensitive enteropathy, and non-celiac gluten sensitivity or NCGS. Both conditions share a number of symptoms such as abdominal and intestinal swelling, diarrhea, headaches and neurological problems, including gluten ataxia. However, unlike celiac disease, NCGS is not an autoimmune condition. In celiac disease, the immune system views gluten as a foreign invader to demolish, a process that inflames the small intestine’s lining and destroys the finger-like projections called villi that aid digestion. This damage causes malabsorption of nutrients, resulting in anemia, fatigue, weight loss, infertility, osteoporosis and, occasionally, cancer. Considering these autoimmune-related problems, many celiacs are particularly wary of the possibility of gluten contamination in oatmeal or increasing risks with bad reactions to oat avenin.

Oats and Avenin

Even carefully processed packages of oats marked “GF” for “gluten free” may pose problems for some gluten-intolerant individuals sensitive to the avenin protein in the grain. Additionally, recent research shows that the avenin in all oat cultivars is not the same. Some kinds of oats cause no sensitivity, whereas others trigger an autoimmune response in some celiacs, according to a University of Seville study published in 2011 by “GUT, An International Journal of Gastroenterology and Hepatology.” To check for avenin sensitivity, people who are gluten intolerant test their response to GF-labeled oats by eating small quantities and waiting to see if they have a reaction. In a family in which more than one person has celiac disease, some may eat GF oats without reaction while others may become ill.

Benefits of Gluten-Free Oats

Cereal grains are praised for their nutritional value and dietary fiber. People who are newly diagnosed with gluten intolerance often yearn for the flavor and texture of grain products. For those who can consume GF oatmeal comfortably, the benefits include far more than culinary pleasure, because oats are well known for helping to control bad cholesterol. Furthermore, based on the University of Seville study, the avenin in at least three varieties of oats received little negative immune response. Even the three most troublesome oat varieties, which presented the strongest evidence of immune-system problems, attracted an attack of antibodies 40 to 400 times less powerful than that of wheat gliadin.

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