Is There Such a Thing as Sugar Intolerance?

Fructose intolerance is a condition in which the body has difficulty digesting fructose, a natural sugar found in fruits, some vegetables, and added sweeteners such as high-fructose corn syrup . There are two main types of this condition: hereditary fructose intolerance, which is a rare genetic disorder, and fructose malabsorption, which is a more common digestive condition. While hereditary fructose intolerance is a lifelong disorder that requires strict dietary management, fructose malabsorption is a nongenetic condition that is often managed through dietary changes. Neither condition is curable, but both are treatable. Here’s everything you need to know about fructose intolerance and how to deal with it.
Types Types of Fructose Intolerance There are two types of fructose intolerance, which have different causes and severity levels: Hereditary Fructose Intolerance This rare, severe genetic disorder occurs when the person lacks aldolase B, an enzyme (a type of protein ) that breaks down fructose.e60dc2a1-f33c-4a05-9b50-8e3e8e597629739a122d-77c4-4a1f-b0b2-17a1496f759f It’s typically diagnosed by early childhood and requires strict, lifelong avoidance of fructose, sucrose (table sugar), and sorbitol (a sugar alcohol that occurs naturally in some fruits and is found in many sugar-free products) to prevent serious complications, such as organ damage.e60dc2a1-f33c-4a05-9b50-8e3e8e597629e46eb049-3afe-40a9-9ef7-b6d7485ef5ba Fructose Malabsorption Also known as dietary fructose intolerance, this is a more common, nongenetic condition in which the small intestine doesn’t absorb fructose properly, says Dana Zhao, MD , a gastroenterologist at Manhattan Gastroenterology in New York City. It results in gastrointestinal (GI) symptoms, but it doesn’t cause long-term organ damage.
Symptoms Signs and Symptoms of Fructose Intolerance Understanding the distinct symptoms of each type of fructose intolerance can help you get the proper diagnosis and treatment.
Nausea and vomiting Abdominal pain Diarrhea Bloating Gas Low blood sugar Symptoms of hereditary fructose intolerance include:e60dc2a1-f33c-4a05-9b50-8e3e8e597629739a122d-77c4-4a1f-b0b2-17a1496f759f Nausea Vomiting Abdominal pain Diarrhea Bloating Low blood sugar ( hypoglycemia ) Meanwhile, dietary fructose intolerance can cause:e60dc2a1-f33c-4a05-9b50-8e3e8e5976293c057bb3-2837-480c-be08-a06fd3dc6f5a Gas Bloating Diarrhea Stomach pain For both conditions, symptoms arise after eating foods that contain fructose, such as:e60dc2a1-f33c-4a05-9b50-8e3e8e5976295320bd3d-f085-4e2d-8807-68006554138e Sweeteners such as high-fructose corn syrup, honey , and agave Most fruits, including apples , pears, sweet cherries , prunes, and dates Vegetables such as asparagus , broccoli , onions, and tomatoes
Causes Causes and Risk Factors of Fructose Intolerance Hereditary fructose intolerance is caused by a mutation in the ALDOB gene. This gene provides your body with instructions for making aldolase B, an enzyme that breaks down fructose in the liver and kidneys.e60dc2a1-f33c-4a05-9b50-8e3e8e597629739a122d-77c4-4a1f-b0b2-17a1496f759f But due to the genetic mutation, the body can’t make adequate amounts of aldolase B. Without enough of this enzyme, the body can’t process fructose, says Dr. Zhao. Fructose malabsorption, on the other hand, isn’t inherited, and the cause isn’t clearly understood. “It’s believed to be caused by impaired absorption of fructose in the small intestine,” Zhao says. Malabsorption may happen when the body doesn’t produce enough of the proteins needed to absorb fructose, or when those proteins aren’t working as they should.e60dc2a1-f33c-4a05-9b50-8e3e8e5976296c592731-c5df-49a6-9a9e-efc7811bcac9 “This results in unabsorbed fructose reaching the colon, where it’s fermented by bacteria, leading to gastrointestinal symptoms,” Zhao says. Malabsorption may also be triggered by underlying inflammatory gut conditions, such as celiac disease (an autoimmune disorder where the body reacts to gluten, a protein in wheat) or Crohn’s disease (a chronic disease that causes inflammation in the digestive tract), adds James Tudor Cox, MD , a gastroenterologist and assistant professor at Texas Christian University’s Burnett School of Medicine.
Diagnosis How Is Fructose Intolerance Diagnosed? Diagnosing hereditary fructose intolerance typically involves a genetic test that examines changes in the ALDOB gene, which is responsible for the body’s breakdown of fructose. The test is most often done using a blood or saliva sample collected at a clinic or specialized lab. A healthcare provider (often a gastroenterologist or geneticist) will typically order this test if someone has symptoms of fructose intolerance (such as severe abdominal pain, low blood sugar, or liver issues) and other common digestive conditions have been ruled out. In some cases, a referral to a genetic counselor may be part of the process to help explain testing and results.e60dc2a1-f33c-4a05-9b50-8e3e8e597629739a122d-77c4-4a1f-b0b2-17a1496f759f To diagnose fructose malabsorption, your physician may recommend a two-week trial where you cut out foods high in fructose (like apples, honey, and certain sweeteners) and see whether your symptoms improve, says Zhao. If they do, that’s often enough to suggest fructose may be the issue. Still, this method isn’t always conclusive. Because fructose is often paired with other sugars, such as sucrose, it can be difficult to know whether symptoms are caused by fructose itself or by another component in the food, says Dr. Cox. That’s where a diagnostic hydrogen breath test can help. In this test, you drink a solution containing 25 grams of fructose when you arrive at the lab or doctor’s office, and then breathe into a collection bag at regular intervals. The goal is to measure the amount of hydrogen in your breath over time. This test works because when your body doesn’t absorb fructose properly, the sugar gets fermented by gut bacteria, producing hydrogen gas that can be detected in your breath.e60dc2a1-f33c-4a05-9b50-8e3e8e597629739a122d-77c4-4a1f-b0b2-17a1496f759f
Treatment Treatment and Medication Options for Fructose Intolerance There is no cure for either form of fructose intolerance. But both conditions can be successfully managed with dietary changes. Treating Hereditary Fructose Intolerance The most impactful treatment for people with hereditary fructose intolerance is to avoid certain sugars for life. This includes fructose, sucrose, and sorbitol, says Ozlem Pinar Bulut, MD , a pediatric gastroenterologist and hepatologist at Phoenix Children’s. Eating even a small amount of fructose can lead to serious health problems, so strict dietary management is essential. Work with a registered dietitian to create an eating plan that provides the necessary nutrients to maintain your health without triggering symptoms. Treating Dietary Fructose Intolerance Dietary fructose intolerance doesn’t always mean cutting out fructose completely, but it usually involves limiting how much you eat, says Zhao. Many people find relief with a fructose-restricted plan, which is often part of a low-FODMAP diet . This eating approach eliminates certain difficult-to-digest carbohydrates. This usually involves temporarily removing high-fructose foods and then slowly reintroducing them one by one to see which triggers symptoms. This step-by-step process helps people pinpoint and avoid their personal triggers.e60dc2a1-f33c-4a05-9b50-8e3e8e59762974a5f026-1269-4a38-af47-9a3973ea7ae4 It’s important to work with a registered dietitian and your doctor to get an accurate diagnosis and to determine a sustainable long-term eating and treatment plan. Restricting foods and food groups unnecessarily can lead to vitamin and mineral deficiencies, says Dr. Bulut.
Prevention Prevention of Fructose Intolerance Hereditary fructose intolerance is a genetic disease, and, therefore, cannot be prevented, says Zhao. However, you can dodge symptoms and severe complications by strictly avoiding fructose, sucrose, and sorbitol throughout your life.e60dc2a1-f33c-4a05-9b50-8e3e8e5976293c057bb3-2837-480c-be08-a06fd3dc6f5a Fructose malabsorption also can’t be prevented, but limiting high-fructose foods often helps alleviate symptoms for those affected.e60dc2a1-f33c-4a05-9b50-8e3e8e5976293c057bb3-2837-480c-be08-a06fd3dc6f5a
Lifestyle Changes Lifestyle Changes for Fructose Intolerance Managing fructose intolerance involves changing your daily habits. Here are some tweaks to consider:e60dc2a1-f33c-4a05-9b50-8e3e8e5976293c057bb3-2837-480c-be08-a06fd3dc6f5a Avoid high-fructose foods. Limiting high-fructose foods in your diet — or eliminating them altogether — is the most effective way to prevent or reduce symptoms of fructose intolerance. High-fructose foods include fruits (especially fruit juice and dried fruits), some vegetables, wheat-containing products, sugar-sweetened soda, and sweeteners (such as honey and high-fructose corn syrup). Read food labels carefully. Individuals with hereditary fructose intolerance and dietary fructose intolerance should be aware of hidden sources of fructose, sucrose, and sorbitol, which may be listed under different names. For example, fructose may be listed as high-fructose corn syrup, fruit juice concentrate, or agave; sucrose may be labeled as cane sugar; and sorbitol is often listed as a sugar alcohol. Checking labels for these terms can help prevent accidental exposure and keep symptoms under control. Work with a registered dietitian. A registered dietitian can create an eating plan tailored to your specific needs. This guidance helps ensure you avoid problem foods without missing out on essential nutrients or unnecessarily restricting your diet, says Zhao.
Prognosis and Outlook How Long Does Fructose Intolerance Last? Hereditary fructose intolerance is a lifelong genetic condition. People with hereditary fructose intolerance must carefully manage their diet continuously to avoid serious complications and maintain their health, according to Zhao. Fructose malabsorption can also last a long time, sometimes indefinitely. However, Zhao says that dietary changes can significantly improve or control symptoms.
Complications Complications of Fructose Intolerance People with hereditary fructose intolerance don’t have the enzyme needed to break down fructose. So, when they eat fructose, the liver can’t properly convert stored glycogen into glucose. This can cause dangerously low blood sugar and a buildup of toxic substances in the liver. Over time, the toxic buildup can damage both the liver and the kidneys, sometimes leading to life-threatening complications if the condition isn’t managed.e60dc2a1-f33c-4a05-9b50-8e3e8e597629e9b6c553-b3c0-4564-bbd2-aef7ea648ffe While not life-threatening, fructose malabsorption can also take a toll. Ongoing GI symptoms — like bloating, pain, and irregular bowel movements — can interfere with eating habits, social situations, and overall well-being. “Fortunately, complications are extremely rare and the treatment is predominantly focused on symptom control,” says Cox.
Related Conditions Related Conditions Fructose intolerance — especially fructose malabsorption — can occur alongside other conditions. It’s most commonly associated with irritable bowel syndrome (IBS, a GI disorder that causes gut sensitivity), says Zhao. Both fructose malabsorption and IBS cause symptoms like bloating, abdominal pain, and changes in bowel movements. A low-FODMAP diet, which limits certain fermentable carbohydrates like fructose, is often helpful for managing both conditions.e60dc2a1-f33c-4a05-9b50-8e3e8e59762997224444-3ec0-4cd6-a707-882f4d9d1c35 Similarly, some people with fructose intolerance also have trouble digesting other carbohydrates, like lactose (a sugar found in milk) or starches (complex carbohydrates found in grains, vegetables, and fruits), says Cox. That’s why it’s essential to keep a close eye on what you eat and how your body reacts. Tracking your symptoms can help you determine whether fructose is the sole trigger or if other sugars are also contributing to the issue, he adds. Systemic sclerosis is a rare autoimmune disease that causes the skin, internal organs, and digestive tract to become hardened and tightened. It may also be linked to fructose malabsorption. One small study found that up to 40 percent of people with systemic sclerosis also experience difficulty absorbing fructose. Systemic sclerosis impairs your gut’s ability to absorb specific nutrients, which may include fructose in some people.e60dc2a1-f33c-4a05-9b50-8e3e8e59762986da7f79-3ee7-4feb-b9be-40c26952e974
The Takeaway There are two types of fructose intolerance: hereditary fructose intolerance (a rare genetic condition) and fructose malabsorption (a dietary condition in which the gut can’t absorb fructose properly). Hereditary fructose intolerance is rare but serious, requiring lifelong dietary restrictions to prevent organ damage. Fructose malabsorption is more common, and limiting fructose-containing foods can prevent, manage, or even improve symptoms. Regardless of which type of fructose intolerance you have, it’s a good idea to work with a registered dietitian who can help you determine which foods to avoid while meeting your nutritional needs.