What Is Fructose Intolerance?

You thought you were doing the healthy thing by making a fruit smoothie. But now your stomach is screaming. Could fructose intolerance be the culprit?

Fructose is a simple sugar. It’s naturally found in fruits and some vegetables. For people with fructose intolerance, an innocent wedge of watermelon or handful of raisins can be a total day wrecker.

“Fructose intolerance is defined by a constellation of symptoms including flatulence, bloating, diarrhea and abdominal pain,” says gastroenterologist Alberto Rubio-Tapia, MD. In other words, it stinks. Find out if fructose intolerance could be causing your discomfort.

There are 2 types of fructose intolerance

The term “fructose intolerance” can be a bit confusing. That’s because it refers to two different conditions, with very different outcomes:

1. Dietary fructose intolerance.
2. Hereditary fructose intolerance.

Dietary fructose intolerance

If you have dietary fructose intolerance, cells in your intestine don’t absorb fructose as they should. There aren’t good estimates of how many people have it, says Dr. Rubio-Tapia. But it’s fairly common.

In people with dietary fructose intolerance (sometimes called fructose malabsorption), eating foods high in fructose can lead to uncomfortable symptoms, including:

• Gas.
• Bloating.
• Diarrhea.
• Stomach pain.

Hereditary fructose intolerance

This is a genetic condition in which people are born without an enzyme that breaks down fructose. Without this enzyme, they can’t digest fructose at all.

Symptoms show up soon after babies start eating their first solid foods. These babies typically show signs including:

• Nausea.
• Bloating.
• Diarrhea.
• Vomiting.
• Abdominal pain.
• Low blood sugar.
• Strong dislike of sweets.
• Problems with growth and development.

Unlike dietary fructose intolerance, hereditary fructose intolerance can cause serious illness. Undigested fructose can build up in the body, damaging the liver and kidneys. If someone with the disorder keeps eating fructose, it can eventually lead to seizures, coma and organ failure.

Genetic testing can confirm a diagnosis of hereditary fructose intolerance. People who have the condition should work with a nutritionist or dietitian to avoid fructose altogether. By cutting out the sugar, they can lead healthy, active lives.

Diagnosing dietary fructose intolerance

Unfortunately, diagnosing dietary fructose intolerance isn’t always simple. Symptoms can sometimes overlap with other conditions, such as irritable bowel syndrome. “There’s no single test we can do to be 100% sure,” says Dr. Rubio-Tapia.

Doctors can perform a fructose breath test to measure how much methane and hydrogen a patient breathes out after drinking a liquid with fructose. That isn’t completely conclusive but can point doctors toward a diagnosis.

Your healthcare provider will also ask about your eating patterns to look for clues. It can help to keep a food log of your symptoms so you can track whether they show up after high-fructose meals.

How to manage dietary fructose intolerance

For people with dietary fructose intolerance, there is no one-size-fits-all solution, says Dr. Rubio-Tapia. “Most people can tolerate some fructose, but everyone has a different sensitivity to it,” he says.

If you suspect fructose intolerance, your doctor will probably recommend an elimination diet. For several weeks, you won’t consume any fructose. Then you can slowly begin reintroducing fructose-containing foods to find out how much you can tolerate without symptoms.

“It’s helpful to work with a dietitian during this process to find what works and make sure you’re still getting adequate nutrition,” he says.

High-fructose foods to avoid (and lower-fructose fruits to try)

Most fruits contain fructose, but there are exceptions. And some non-fruit foods have hidden fructose. High-fructose corn syrup is a common sweetener found in everything from yogurt to soda, so it’s important to read labels.

Common high-fructose foods include:

• Most fruits, especially dried fruits and fruits canned in juice or syrup.
• Vegetables including artichoke, asparagus, broccoli, leeks, mushrooms, okra, onions, peas, red pepper, shallots and tomato products.
• Foods with wheat as the main ingredient, such as wheat bread and pasta.
• Sweeteners such as honey, agave nectar and high-fructose corn syrup.
• Sodas and desserts sweetened with fructose.

Fortunately, some fruits fall on the lower end of the fructose scale. Some people with dietary fructose intolerance have luck with these lower-fructose picks:

• Avocadoes.
• Bananas.
• Cranberries.
• Cantaloupe.
• Lemons and limes.
• Oranges.
• Pineapple.
• Strawberries.

“Some people may be able to tolerate certain fruits better than others. Listen to your body,” Dr. Rubio-Tapia says. It might take some trial and error, but your happy stomach will thank you.