If you’ve been avoiding gluten because it makes your gut feel miserable, yet are still struggling with frequent gas and bloating, you could be reacting to fructans.

Besides gluten, wheat contains a number of substances that can cause unpleasant symptoms. One example is fructans, or natural carbohydrates found in plants in varying amounts.

Many people with gastrointestinal (GI) complaints feel better when on a gluten-free diet simply because they are cutting out a major source of fructans. Research reveals that gluten may be getting a bad rap for the problems caused by fructans.

Upward Trend in Gluten Problems

There are a number of reasons someone might be sensitive to gluten. Most are well understood, except for the elusive nonceliac gluten or wheat sensitivity. There is no way to test for this condition and no clear mechanism behind it. Its symptoms overlap with those of other conditions, such as celiac disease.

Celiac disease is the most serious reason to avoid wheat or gluten. It’s an autoimmune disorder in which gluten damages the small intestine, prevents nutrient absorption, and causes long-lasting and chronic digestive symptoms.

A wheat allergy happens when the immune system responds to wheat by making immunoglobulin E antibodies, which release chemicals causing allergies affecting the nose, throat, lungs, or skin.

Gluten sensitivity can cause symptoms in both the gut and immune system, Dr. Elizabeth Boham, a physician and dietitian who specializes in functional medicine, told The Epoch Times via email. Symptoms can include fatigue, eczema, itchy skin, brain fog, joint pain, headaches, and gut symptoms such as bloating, gas, diarrhea, constipation, and pain.

People with fructan intolerance respond to wheat with a nonimmune mediated reaction, meaning symptoms are limited to the gut.

Fructan intolerance is caused by an imbalance of gut microbes, including a lack of those that digest carbohydrates. That causes the fibers to ferment in the gut, causing gas, bloating, pain, and changes in bowel movements, such as diarrhea or constipation.

Complicated Nature of Fructans

Fructans are a type of FODMAP, an acronym for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. These are short-chain carbohydrates poorly absorbed by the small intestine. Other FODMAPs are typically single molecules, with some being sugar alcohols, such as sorbitol and mannitol, and others being simple sugars, such as fructose and lactose.

The FODMAP fructan is a chain of fructose sugar molecules with a glucose sugar molecule at the end. They vary in length and structure, making them complex to measure.

FODMAPs span food groups. Fructans are found in a wider variety of food groups than other FODMAP foods, including grains, fruits, and vegetables. This can make it harder to eliminate fructans from the diet.

Foods with both gluten and fructan include wheat, barley, rye, and spelt.

Gluten-free foods with fructan include fruit, legumes, vegetables, and nuts, such as bananas, dates, watermelon, chickpeas, black beans, kidney beans, beets, Brussels sprouts, shallots, chicory root, leeks, almonds, cashews, and pistachios.

The Bigger Villain Fructan

Patients with nonceliac gluten or wheat sensitivity helped researchers test the hypothesis that fructans could be causing their symptoms rather than gluten.

A 2024 study published in BMC Medicine showed that patients were more likely to react with GI symptoms after eating fructan bars than gluten bars. However, researchers were unable to find the precise mechanism causing this.

The investigators examined the composition of the fecal microbiota before and after dietary changes but did not discover shifts in microbes that explained why fructans caused more problems. One thing apparent among the 59 participants in the study was that a person’s baseline bacterial composition seemed to influence GI symptoms.

Participants were randomly assigned to eat a diet containing gluten, fructan, or a placebo—concealed in muesli bars—for seven days. After another seven days to reset their GI tracts, or longer if needed, they crossed over into a different group until they completed all three diets.

They rated their symptoms on an irritable bowel syndrome scale—13 gave gluten the highest scores; 24, fructan; and 22, placebo.

The results illustrate a common misconception dietitians often deal with, according to Ashley Oswald, dietitian and owner of Oswald Digestive Clinic.

“It’s very common for people to think it’s the gluten, and they might continue to think this unless they’re working with a gut health dietitian or someone specialized in this information,” she told The Epoch Times.

Symptoms caused by fructan typically take a few days to a couple of weeks to clear, whereas those caused by gluten may not improve for 21 days.

Best Bet: Elimination Diet

Elimination diets are the gold standard for diagnosing food sensitivities, although some tests are used for detecting issues with gluten or FODMAP foods.

In addition to allergy testing for wheat and gluten, which won’t necessarily indicate sensitivities, you can test for small intestinal bacterial overgrowth, or an imbalance of bacteria in the small intestine that causes reactions to high FODMAP foods.

However, the tests aren’t always reliable, Boham said.

“We will often do a low FODMAP diet for a period of time and see if this helps the gas, pain, bloating, distention, diarrhea, and constipation,” she said. “If it does, then we will reintroduce some of the high FODMAP foods.”

Elimination diets typically last for two to six weeks, she said, and it can be helpful to work with a professional to reintroduce foods slowly and monitor reactions.

Monash University, where the low-FODMAP diet originated, also has an app that can help guide people through the elimination and reintroduction of food.

Oswald said most people don’t care to dig very deep into the reasoning behind their symptoms. They often try a gluten-free diet, feel much better, and never know what it is in the wheat that is causing the aggravation.

There can be other factors at play, too, such as how much bread and wheat people eat and whether they substitute it for other carbohydrates, as this can cause blood sugar imbalances that can produce similar inflammatory problems as both gluten and fructan.

“It’s not so black and white since people can have a fructan intolerance and gluten sensitivity at the same time,” Oswald said. “It’s often the same elimination process. Cut out the food, and see if symptoms improve.”

Unnecessary food avoidance could be keeping you from healing your GI tract. If fructan is causing problems, Boham said you may be able to eventually enjoy the benefits of fiber-rich fructan foods after a period of elimination and reintroduction. They are essential in a balanced diet.

“You can get needed carbohydrates from starchy vegetables (sweet potatoes) and other gluten-free grains (quinoa and rice) for example,” she said. “So there are no long-term dangers of avoiding gluten. In addition, high-FODMAP foods are prebiotics for the gut microbiome. This means this fiber is good to help feed the healthy bugs in our gut.”