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What Is Fructose Malabsorption?

The short answer: Hold the honey

Malia Jacobson

Published on: March 21, 2018

Little girl eating apple

When Mia Lancaster’s oldest son, then 4-year-old Mason, began experiencing stomach cramps along with a distended belly, diarrhea and disturbed sleep, the family was living in Central America on a 15-month work assignment. Their local doctor suspected a common parasitic infection and prescribed anti-parasite meds, but Mason’s symptoms didn’t improve. 

A few months later, the family returned home to Tacoma. After their pediatrician ruled out parasites and other infections, Mia started searching more intently for the source of Mason’s pain. 

Nearly a year after his symptoms began, a simple breath test at Seattle Children’s Hospital uncovered the source of his discomfort: fructose malabsorption, a surprisingly common condition most have never heard of.

What is FM?

For both kids and adults, fructose malabsorption happens when the body can’t break down and digest fructose, a type of naturally occurring sugar found in fruits, vegetables, honey, wheat and table sugar (sucrose).

Unlike hereditary fructose intolerance (HFI), a serious metabolic disorder diagnosed with a liver biopsy, fructose malabsorption is diagnosed with a test that measures levels of hydrogen and other gases in the breath after fructose is consumed. 

Like Mason, many kids aren’t tested for fructose malabsorption until they’ve been through rounds of tests for other disorders; conditions like lactose intolerance and gluten intolerance may be tested first.

A 2010 study of children with recurrent abdominal pain found that 53.9 percent of the kids tested positive for the condition.  

But researchers at Tacoma’s Mary Bridge Children’s Hospital say fructose malabsorption is an under-recognized source of gut pain for kids. Their 2010 study of children with recurrent abdominal pain found that 53.9 percent of the kids tested positive for the condition.  

Menu makeover

Fructose malabsorption is primarily treated by avoiding certain foods to minimize digestive distress, so Mason’s diagnosis meant an unexpected diet overhaul for the already health-conscious family. 

“We were given a list of foods to choose, foods to limit and foods to avoid,” Mia says. Not surprisingly, high-fructose corn syrup was out, but Mason didn’t consume a lot of that to begin with. More shocking was the fact that they’d have to limit or eliminate lots of vegetables, wheat and other stealthy sources of fructose. 

Since kids thrive on routine and familiarly, particularly when it comes to food, radically changing a child’s diet is tough, especially when there’s a long list of foods to avoid.

And since the list of offending foods include nutritious ones most parents try to include in their child’s healthy diet, like broccoli, carrots, apples, tomatoes, cauliflower, dried fruit and fruit-flavored yogurts, the diagnosis can throw a health-conscious family’s diet off-kilter. Case in point: Seemingly wholesome honey is off the table thanks to high fructose levels, while white table sugar is allowed in moderation. Say what?!

Switching to a low-fructose diet can involve a shift in thinking for parents; goodbye, staples like veggie trays, apple slices, yogurt tubes and pizza; hello, beets, potatoes, nuts and legumes. After Mason’s diagnosis, he started to dread birthday parties because they’d invariably feature a slew of foods he couldn’t have, says Mia.

Happy bellies

But sticking to a low-fructose diet pays off — and fast. Kids who follow a low-fructose diet can see symptoms improve or disappear within a day or two, though some may take longer, says Dr. Dale Lee, gastroenterologist and director of the Celiac Disease Program at Seattle Children’s. And happily, many children outgrow the condition after age 5 as their digestive system matures. 

These days, 7-year-old Mason’s diet limitations have mellowed along with his symptoms. He doesn’t have stomach problems unless he eats a lot of fructose, Mia says, and he self-regulates by choosing foods low in fructose most of the time. 

“Every now and then he’ll go to a birthday party and eat pizza and cake and end up bloated with a tummy ache, but he recognizes that it’s a trade-off. We let him manage that to an extent,” she says. “He has a lot of knowledge about his body, and a lot of self-control.” 

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