What is gluten? Gluten-free foods and diet


What is gluten?

Gluten is a protein composite that is found in grains such as wheat, barley, rye, and triticale (a cross between wheat and rye). It is formed when two proteins, glutenin and gliadin, combine in the presence of water. Gluten provides elasticity to dough and helps bread and other baked goods rise properly. It is also used as a binding agent in many processed foods, such as sausages and sauces.

However, some people are sensitive to gluten and may experience adverse reactions when they consume it. Celiac disease is an autoimmune disorder in which the body mistakenly attacks the small intestine when gluten is ingested. This can lead to damage of the intestinal lining and malabsorption of nutrients, resulting in various symptoms such as abdominal pain, bloating, diarrhea, and weight loss.

Non-celiac gluten sensitivity (NCGS) is another condition in which individuals experience symptoms similar to those with celiac disease when they consume gluten, but they do not have the characteristic intestinal damage or other markers of celiac disease. NCGS is still a topic of ongoing research, and its mechanisms are not yet fully understood.

Avoiding gluten is not necessary for everyone. However, some people choose to avoid it for personal or dietary reasons, such as following a gluten-free diet for weight loss or for managing certain health conditions.

Is gluten bad for you?

Gluten is not inherently bad for everyone, but it can be problematic for individuals who have celiac disease or non-celiac gluten sensitivity (NCGS). In these cases, gluten can trigger an immune response that can damage the intestinal lining and cause a range of symptoms, including abdominal pain, bloating, diarrhea, and fatigue. For people with these conditions, avoiding gluten is essential to managing their health.

However, for the general population without gluten sensitivity, there is no evidence to suggest that a gluten-free diet is necessary or beneficial. In fact, some research suggests that a gluten-free diet may be less nutritious than a diet that includes gluten-containing whole grains, as gluten-free products are often lower in fiber and certain vitamins and minerals.

Some people may also experience symptoms similar to gluten sensitivity due to other factors, such as FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) or other food intolerances. If you suspect that you may have a gluten sensitivity or other food intolerance, speak with a gastroenterologist to determine the underlying cause of your symptoms and receive appropriate treatment.

Gluten-free foods

Here is a list of gluten-free foods:

  • Fruits and vegetables
  • Meat, poultry, and fish (fresh or frozen)
  • Legumes (beans, lentils, chickpeas)
  • Nuts and seeds
  • Dairy products (milk, cheese, yogurt)
  • Gluten-free grains (rice, corn, quinoa, amaranth, millet, sorghum)
  • Gluten-free flours (almond flour, coconut flour, rice flour, chickpea flour, potato flour, tapioca flour)
  • Gluten-free pasta (made from rice, corn, or other gluten-free grains)
  • Gluten-free bread and baked goods (made with gluten-free flours and ingredients)
  • Gluten-free snacks (such as popcorn, potato chips, fruit snacks, and gluten-free crackers)

Some packaged foods may contain hidden sources of gluten, so you need to read the labels carefully and look for gluten-free certifications. Additionally, some products that are naturally gluten-free may become contaminated with gluten during processing, so choose products that are certified gluten-free or labeled as such by the manufacturer.

Gluten-free beverages

Here are some examples of gluten-free beverages:

  • Water (still, sparkling, flavored)
  • 100% fruit and vegetable juices (without added sweeteners)
  • Coffee (black or with dairy-free milk)
  • Tea (black, green, herbal, fruit-infused)
  • Milk (dairy or non-dairy, such as almond, soy, or coconut milk)
  • Soft drinks (check labels for gluten-containing ingredients)
  • Sports drinks (check labels for gluten-containing ingredients)
  • Wine (all types, including red, white, and sparkling)
  • Distilled spirits (such as vodka, gin, rum, and tequila)
  • Beer made with gluten-free grains, such as sorghum or rice (not all beers labeled “gluten-free” are suitable for people with celiac disease, as they may still contain traces of gluten)

Are spirits gluten-free?

Most distilled spirits, including vodka, gin, whiskey, and rum, are considered gluten-free. The distillation process involves heating the liquid to create steam, which is then collected and condensed back into a liquid. Since gluten proteins do not vaporize, they are left behind in the distillation residue, and the resulting spirits are generally considered gluten-free.

However, some people with celiac disease or gluten sensitivity may still experience symptoms after consuming certain distilled spirits, as some manufacturers may use ingredients that contain gluten during the distillation process or add gluten-containing flavorings after distillation. Additionally, some premixed alcoholic beverages may contain gluten or other ingredients that are not gluten-free.

If you have celiac disease or gluten sensitivity, you should read the labels carefully and look for products that are certified gluten-free or labeled as such by the manufacturer. You may also want to consult with a gastroenterologist or registered dietitian to determine what foods and beverages are safe for you to consume.

Are oats gluten-free?

Oats are technically gluten-free, but they can be contaminated with gluten during processing. This is because oats are often grown, harvested, and processed in facilities that also handle wheat, barley, and other gluten-containing grains. As a result, some commercial oat products may contain small amounts of gluten.

For people with celiac disease or gluten sensitivity, they should choose oats that are labeled as gluten-free or certified gluten-free by a third-party organization. These oats are grown and processed in dedicated gluten-free facilities and are tested to ensure that they contain less than 20 parts per million (ppm) of gluten, which is the threshold set by the FDA for gluten-free labeling.

Some people with celiac disease or gluten sensitivity may still experience symptoms when consuming even certified gluten-free oats, as some individuals may be sensitive to a protein in oats called avenin. If you have celiac disease or gluten sensitivity, talk to a gastroenterologist or registered dietitian to determine whether oats are safe for you to consume.

How to read food labels properly if I’m looking for gluten-free foods?

If you’re looking for gluten-free foods, it’s important to carefully read food labels. Here are some things to pay attention to:

  1. Look for the words “gluten-free”: If a product is labeled “gluten-free,” it means that it contains less than 20 parts per million (ppm) of gluten. This is the threshold that has been established by the FDA for a food to be considered gluten-free.
  2. Check the ingredient list: Wheat, barley, and rye are the most common sources of gluten in food. Look for these ingredients on the label and avoid products that contain them.
  3. Beware of cross-contamination: Even if a product doesn’t contain gluten, it may have come into contact with gluten during manufacturing. Look for products that are labeled “certified gluten-free,” as these have been tested and verified to be free of gluten.
  4. Know which grains are gluten-free: There are many grains that are naturally gluten-free, such as rice, corn, quinoa, and buckwheat. Look for products that contain these grains instead of wheat, barley, or rye.
  5. Be wary of additives: Some food additives, such as modified food starch, can be made from gluten-containing grains. If you see these additives on the label, be sure to confirm with the manufacturer whether they are gluten-free.
  6. Check for hidden sources of gluten: Gluten can sometimes be found in unexpected places, such as soy sauce, beer, and some types of vinegar. Look for products that are specifically labeled “gluten-free” or “no gluten-containing ingredients.”
  7. Understand “may contain” warnings: Some food labels include a “may contain” statement that indicates the product may have come into contact with gluten during production. While these warnings are not required by law, they can help you make an informed decision about whether to consume a particular product.
  8. Look for gluten-free certification logos: Some organizations certify products as gluten-free. Look for logos from organizations such as the Gluten-Free Certification Organization (GFCO), which indicates that a product has been independently verified to meet gluten-free standards.
  9. Be aware of different gluten-free standards: Different countries and organizations may have different standards for what is considered gluten-free. For example, the European Union defines gluten-free as less than 20 ppm, while Australia and New Zealand define it as less than 3 ppm. Be sure to check the standards for your country or region to ensure that you’re following the appropriate guidelines.
  10. Don’t rely solely on food labels: While food labels can be a helpful tool, it’s important to remember that they are not always 100% reliable. If you’re uncertain about whether a product contains gluten, contact the manufacturer or look for additional information from a trusted source.

Varieties of wheat that contain gluten

All varieties of wheat contain gluten, including:

  • Durum wheat: a hard, high-protein wheat used to make pasta, couscous, and some types of bread
  • Spelt: an ancient variety of wheat that is high in protein and is sometimes used in bread, pasta, and cereal products
  • Emmer: another ancient variety of wheat that is similar to spelt and is sometimes used in bread and pasta products
  • Einkorn: one of the oldest known varieties of wheat, often used to make bread and pasta
  • Kamut: a large-grain wheat that is sometimes used in bread and pasta products

Other gluten-containing grains include barley, rye, triticale (a hybrid of wheat and rye), and some varieties of oats (due to cross-contamination during processing). People with celiac disease or gluten sensitivity should avoid all of these grains and choose gluten-free alternatives instead.

Varieties of flour that contain gluten

Flours made from gluten-containing grains contain gluten. Here are some of the most common types of flour that contain gluten:

  • Wheat flour (including all-purpose flour, bread flour, cake flour, and pastry flour)
  • Barley flour
  • Rye flour
  • Spelt flour
  • Kamut flour
  • Triticale flour

Even flours that are not made from gluten-containing grains may be processed in facilities that also handle wheat, barley, and rye, and may be contaminated with gluten. For this reason, people with celiac disease or gluten sensitivity should choose flours that are labeled as gluten-free or certified gluten-free by a third-party organization, or use alternative flours that are naturally gluten-free, such as almond flour, coconut flour, rice flour, or chickpea flour.

Processed foods that contain gluten

Gluten is commonly found in processed foods and can be listed under different names in the ingredients list. Here are some examples of processed foods that often contain gluten:

  • Baked goods (bread, pastries, cakes, cookies, etc.)
  • Breakfast cereals (especially those made with wheat or barley)
  • Pasta and noodles (made with wheat, spelt, or other gluten-containing grains)
  • Processed meats (such as sausages, hot dogs, and deli meats, which may contain fillers and binders made with wheat or other gluten-containing grains)
  • Condiments (such as soy sauce, teriyaki sauce, Worcestershire sauce, and salad dressings, which often contain wheat or barley)
  • Snack foods (such as crackers, pretzels, and chips, which are often made with wheat flour)
  • Soups and broths (which may contain wheat flour as a thickener or flavor enhancer)
  • Frozen dinners and pre-packaged meals (which may contain wheat or other gluten-containing grains in the sauces or fillings)
  • Beer and other alcoholic beverages made with barley, wheat, or rye
  • Flavored coffees and teas (which may contain barley malt or other gluten-containing ingredients)
  • Energy bars and protein bars (which often contain oats or other grains that may be contaminated with gluten)
  • Frozen desserts (such as ice cream and frozen yogurt, which may contain gluten-containing ingredients or be cross-contaminated during processing)
  • Gravies and sauces (such as roux-based sauces or canned gravies, which often contain wheat flour as a thickener)
  • Instant pudding mixes and dessert mixes (which may contain modified food starch, a common source of gluten)
  • Meat substitutes (such as vegetarian burgers, which may contain wheat gluten as a protein source)
  • Seasonings and spice blends (which may contain wheat or barley malt as a filler or flavor enhancer)
  • Supplements and medications (which may contain gluten as a filler or binder)

How to avoid gluten when eating in a restaurant?

Avoiding gluten when eating in a restaurant can be challenging, but there are several steps you can take to reduce the risk of gluten exposure:

  1. Research the restaurant in advance: Look up the menu online or call ahead to ask if they offer gluten-free options. Some restaurants may even have a separate gluten-free menu or be certified by a gluten-free organization.
  2. Communicate your needs clearly: When you arrive at the restaurant, inform your server that you have a gluten allergy or intolerance and need to avoid gluten in your meal. Explain that this includes all wheat, barley, rye, and cross-contamination from other gluten-containing foods.
  3. Ask questions: Don’t be afraid to ask questions about how dishes are prepared and what ingredients are used. Ask if dishes can be modified to be gluten-free, such as using gluten-free pasta or substituting a salad for bread.
  4. Avoid risky foods: Avoid obvious sources of gluten such as bread, pasta, and wheat-based sauces. Be cautious of fried foods, which may be coated in flour, and dishes that contain soy sauce, which often contains wheat. Choose dishes made with whole foods such as meat, fish, vegetables, and rice, which are less likely to contain hidden sources of gluten.
  5. Consider bringing your own condiments: If you’re not sure about the ingredients in condiments such as salad dressings or sauces, consider bringing your own gluten-free options from home.
  6. Be aware of cross-contamination: Even if a dish is labeled as gluten-free, it can still be contaminated with gluten if it’s prepared on the same surfaces or with the same utensils as gluten-containing foods. Ask if the restaurant has a separate area or kitchen for preparing gluten-free dishes, or if they take steps to prevent cross-contamination.

Is gluten-free diet a weight-loss diet?

A gluten-free diet itself is not a weight-loss diet, and following a gluten-free diet does not guarantee weight loss. However, some people may lose weight when they switch to a gluten-free diet because it often involves cutting out high-calorie processed foods that contain gluten, such as cakes, cookies, and other baked goods.

Additionally, some gluten-free foods, such as fruits, vegetables, lean proteins, and whole grains like quinoa and brown rice, are naturally lower in calories and higher in fiber than their gluten-containing counterparts. This can help people feel fuller for longer and reduce overall calorie intake, which can lead to weight loss.

However, not all gluten-free products are low in calories or healthy. Many gluten-free processed foods, such as breads, crackers, and cereals, are still high in calories, sugar, and fat. Eating too many of these foods can actually lead to weight gain.

What are some of the risks of following a gluten-free diet if you do not have celiac disease?

There are some potential risks associated with following a gluten-free diet if you do not have celiac disease or gluten intolerance. Here are a few:

  1. Nutritional deficiencies: A gluten-free diet may be low in important nutrients such as fiber, iron, and B vitamins. This is especially true if you rely heavily on processed gluten-free foods, which are often low in these nutrients. It’s important to ensure that you’re getting these nutrients from other sources such as fruits, vegetables, lean proteins, and gluten-free whole grains like quinoa and brown rice.
  2. Weight gain: As I mentioned earlier, some gluten-free products are higher in calories and fat than their gluten-containing counterparts. If you consume these products in large amounts, you may actually gain weight instead of losing it.
  3. Social isolation: Following a gluten-free diet can be socially isolating, as it can make it more difficult to eat out, attend social events, and share meals with others. It’s important to find ways to navigate these challenges and maintain a balanced social life.
  4. Increased food costs: Gluten-free products are often more expensive than their gluten-containing counterparts, which can make it more difficult to stick to a budget. It’s important to plan meals and shop strategically to minimize costs.
  5. Unnecessary dietary restrictions: Unless you have celiac disease or gluten intolerance, there is no medical reason to avoid gluten. Cutting out gluten unnecessarily can lead to unnecessary dietary restrictions and make it more difficult to maintain a balanced and varied diet.

If you’re considering a gluten-free diet for reasons other than celiac disease or gluten intolerance, speak with a gastroenterologist to determine if it’s the right choice for you. Your gastroenterologist can help you evaluate your individual needs and make recommendations for a healthy and balanced diet.

Bottom line

Gluten is a protein found in wheat, barley, and rye that can cause an immune reaction in people with celiac disease or gluten intolerance. For these individuals, avoiding gluten is essential to maintain their health.

There is no evidence that a gluten-free diet provides health benefits to people without celiac disease or gluten intolerance. In fact, following a gluten-free diet may increase the risk of nutritional deficiencies, weight gain, and social isolation.

How can I contact gastroenterologist Dr. Zavos for an appointment?

Dr. Chris Zavos is a board-certified gastroenterologist and hepatologist, located in Thessaloniki Greece, and specifically in Kalamaria suburb, about 7 kilometres (4 miles) southeast of downtown Thessaloniki. His private office is at: Fanariou 8 street (near Aigaiou and Adrianoupoleos avenues), Kalamaria (Thessaloniki), Greece.

Thessaloniki International Airport is only 10 km away from his private office in Kalamaria and can be reached by taxi within 13 minutes from the airport.

Dr. Chris Zavos performs endoscopies at Bioclinic private hospital in downtown Thessaloniki (Mitropoleos 86 street).

You can contact Dr. Zavos at phone numbers: (+30)-6976596988 and (+30)-2311283833, or you can email him at czavos@ymail.com. Dr. Zavos responds to Greek and English languages.

Last update: 3 October 2023, 12:33


Gastroenterologist - Hepatologist, Thessaloniki

PhD at Medical School, Aristotle University of Thessaloniki, Greece

PGDip at Universitair Medisch Centrum Utrecht, The Netherlands

Ex President, Hellenic H. pylori & Microbiota Study Group