Most of the time we eat food, our digestive system quietly does its job of processing the food without us even being aware of it. Sooner or later, though, we’ll eat something that unexpectedly leads to gas, bloating, constipation, diarrhea, or any of a number of other gastrointestinal symptoms. In these times it can take some detective skills to figure out what you ate that caused the problem. Sometimes the effects can be seemingly random or otherwise not from a clear source. In a somewhat narrow segment of the population, though, it might be because of fructose intolerance. 

What Is Fructose Intolerance?   

Fructose intolerance, now commonly referred to as fructose malabsorption, is a digestive disorder characterized by the inability to properly absorb fructose. Fructose is a naturally occurring monosaccharide (simple sugar) found in fruits, vegetables, and sweeteners that gets converted by the liver into glucose for energy. A person with fructose malabsorption lacks the necessary enzymes in the small intestine to break down fructose effectively, and this can lead to problems with the gut microbiome that resides in the large intestine.  

When undigested fructose does reach the large intestine, the gut bacteria, through the process of fermentation, consume the fructose and break it down into gasses like hydrogen and methane as well as short-chain fatty acids. The abnormal presence of these gasses and acids can then lead to a variety of gastrointestinal symptoms. The severity of the symptoms depend on a person’s individual sensitivity and the amount of fructose consumed. It’s important to note that fructose malabsorption is different from being allergic to fructose, which is instead an immune response to the consumption of fructose.    

There are essentially two types of fructose intolerance: dietary fructose intolerance and hereditary fructose intolerance. All humans have a limit on the amount of fructose that can be absorbed by the digestive tract, but people with dietary fructose intolerance are much more sensitive to it on average. Hereditary fructose intolerance (HFI), on the other hand, comes from a genetic error that leads to a deficiency of the enzyme aldolase B. Not only does HFI cause various symptoms, but it also can cause a buildup of fructose that can lead to liver damage or liver failure. 

Symptoms of Fructose Malabsorption

When malabsorbed and fermentable fructose is in the large intestine, gut bacteria begin to essentially feed on it. The result of this series of chemical reactions is a set of symptoms that is similar to those of another condition called irritable bowel syndrome (IBS), a functional gastrointestinal disorder that disrupts the normal digestive process. In the case of fructose malabsorption, there a several common symptoms: 

• bloating – a feeling of fullness or distention in the abdomen.
• gas – increased production of intestinal gas that leads to flatulence
• abdominal pain – cramping or discomfort in the abdomen
• diarrhea – frequent loose or watery stools
• constipation – infrequent bowel movements or difficulty passing stools 
• nausea – feeling an urge to vomit or general queasiness 
• fatigue – feeling tired or lethargic (may be related to a nutrient deficiency)
• discomfort – a general sense of discomfort or unease in the digestive system

Like other types of food intolerance (lactose, gluten, sucrose), fructose malabsorption affects different people in different ways; some may experience very mild symptoms while others may have more pronounced and debilitating symptoms. Moreover, most of the associated symptoms can overlap with other digestive disorders; as a result, it can be difficult to diagnose the condition without consultation with a doctor.  

How to Manage Fructose Malabsorption  

For those with fructose malabsorption, managing the condition often goes beyond simply avoiding it because there are so many fructose-containing foods. Most fruits (especially dried fruits) have fructose, but a number of vegetables are also high-fructose foods; examples include artichokes, asparagus, broccoli, leeks, mushrooms, and onions. Most strategies for treating this condition involve some of the following common methods: 

• Limit high-fructose foods: Reducing or avoiding foods high in fructose is essential, and that means limiting fruits (watermelon, apples, grapes, etc.), fruit juices, and sweeteners like table sugar, agave syrup, sorbitol (a type of sugar alcohol), or high-fructose corn syrup. Instead, try low fructose fruits like cranberries, bananas, or pineapple.
• Low-FODMAP diet: One of the most direct ways to manage fructose malabsorption is to switch to a low-FODMAP diet. FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) are foods with carbohydrates that are poorly absorbed in the intestines and are likely to ferment in the colon. A low-FODMAP diet is also considered a low-fructose diet and can help reduce symptoms. 
• Combine with glucose: Consuming fructose in combination with an equal or higher amount of glucose can actually facilitate the absorption of fructose through a shared transporter in the small intestine. Glucose is our body’s main form of energy and can be found in various carbohydrate-containing foods like rice, potatoes, and some fruits.
• Reading labels: Fructose, especially in the form of the highly processed high-fructose corn syrup, can show up in surprising places, so it’s important to become familiar with reading ingredient labels. Fructose is often used in food products like sauces, dressings, and packaged foods.  
• Food diary: It can be hard to keep track of everything you eat on a daily basis, and that’s why keeping a food diary can be helpful. This way you can record potential trigger foods that seem correlated with particular symptoms. 
• Probiotics: Probiotics are substances with live bacteria that are meant to improve the diversity of the gut microbiome. More research is needed, but there is some evidence that probiotics in foods or as supplements may be able to help improve the symptoms of fructose malabsorption.  

Fructose and Body Weight  

In recent years, researchers have been looking more closely at fructose and any impact it may have on metabolism and body weight. Some research has suggested that fructose may stimulate hormones related to weight gain or even fool the body into thinking you’re hungrier than you really are. It’s unclear so far the extent to which this is true, but there may also be other indirect connections between fructose and body weight: 

• Eating more calories: Some people with fructose malabsorption may avoid foods that trigger their symptoms and then try to replace them with other calorie-dense foods that are well-tolerated but not necessarily healthier. Over time, this can lead to an increase in overall caloric intake, potentially contributing to weight gain.
• Insufficient fiber: Restricting certain fruits and vegetables out of fear of their fructose content might lead to a reduced intake of dietary fiber. Dietary fiber plays a role in promoting satiety and supporting healthy digestion, and a lack of it may result in less efficient digestion and potential overeating.
• Emotional eating: Coping with digestive symptoms can be emotionally challenging for some people, and that can lead to emotional eating of comfort foods that are often high in calories and low in nutritional value.

How to Get Help Losing Weight  

Losing weight can be a challenge for almost anyone, and it can be even harder while managing a gastrointestinal condition. If you’ve tried to lose weight in the past but weren’t able to have success, you’re not alone. At True You Weight Loss, we are passionate about helping people turn the corner and finally find the freedom they’ve been looking for. To find out more about your endobariatric weight loss options, please contact us today to request a consultation.