Are Sugar Intolerance Symptoms the Same in Children, Teens, and Adults?

Are Sugar Intolerance Symptoms the Same in Children, Teens, and Adults?

Here are the different signs, from infancy through adulthood. Early diagnosis and treatment are key to making sure your child develops normally.

CSID Symptoms in Kids Vs Adults

The most common symptoms of Sucrose Intolerance caused by Congenital Sucrase-Isomaltase Deficiency (CSID), and informally referred to as “Sugar Intolerance” are frequent, watery diarrhea; bloating; gassiness; stomach pain; and vomiting. There are other symptoms too. They can range from mild to severe, and they can change over time.

Babies and Toddlers

What’s happening. For the first months of your baby’s life, his diet usually consists of breast milk and nothing else. At some point, parents introduce formula, then move on to apple juice, baby food, cereal, and fruits.

The symptoms of CSID may appear when your infant moves on to formula, which contains the sugar called lactose but can also contain starch, which is a chain of sugars linked together.

Your once-happy baby is suddenly miserable, with ongoing watery diarrhea, signs of stomach pain, gassiness, bloating, vomiting, irritability, diaper rash that won’t quit (from all the diarrhea), or any combination of these.

That’s because, beyond breast milk, many foods and food products contain sucrose (table sugar) that is often found in baby formula, juice, and other sweetened drinks or maltose that is found in bread products and cereals.

Baby’s stomach can’t break down these foods because he was born without adequate functioning of certain chemicals, the enzymes sucrase and isomaltase, that are needed to digest the sugars sucrose and maltose.

“Most milk-based formulas use lactose as the carbohydrate,” says Tuvia A. Marciano, DO, Director of Pediatric Inflammatory Bowel Disease and Chief of Pediatric Endoscopy at NYU Winthrop Hospital in Mineola, New York.

“Therefore, we often do not see sucrose-deficiency diarrhea until the introduction of table foods, at the approximate age of nine months.”

For infants who have been diagnosed with CSID, sucrose- and starch-free formulas are available.

What to look for. The classic symptoms of CSID in babies and toddlers include, but are not limited to, the following:

  • Signs of stomach pain, including bloating and gas, especially when your child seems to develop this discomfort right after eating
  • Watery diarrhea, several times a day, most of the time
  • Severe, angry-looking diaper rash
  • Irritability
  • Vomiting
  • Not gaining enough weight

“The nature of the diaper rash is significant,” says Dr. Marciano, “because it’s a sign of acidic bowel movements. Sugar should be absorbed in the small bowel; but in those with CSID, the sucrose passes through to the large intestine without having been absorbed. The bacteria in the large intestine convert the sugar into hydrogen gas, leading to bloating and a very acidic diarrhea.”

In real-people’s terms, this means that, because your baby can’t digest the sugars he is eating, his bowels aren’t working right, the diarrhea doesn’t let up, and his poor little backside doesn’t get relief in order to heal.

Many parents, and even pediatricians, may suspect a food allergy when the diarrhea doesn’t stop after a few days.

But CSID is not an allergy.

It is a rare disease and, because of that, most primary care pediatricians don’t think of it when they make a diagnosis. They don’t see enough babies and kids with Sucrose Intolerance symptoms to recognize it.

Even pediatric gastroenterologists (commonly called pediatric GI doctors), who are specialists in stomach disorders in children, may not first associate your child’s symptoms with sucrose.

That’s because CSID is a copycat condition. Its various symptoms overlap with those of commonly known gastrointestinal (GI) conditions, such as irritable bowel syndrome (IBS), food intolerances to lactose (milk) and gluten, and toddler’s diarrhea.

If your doctor can’t piece together the variety of symptoms your child is displaying, the physician might even say that your baby has two different problems happening at the same time.

Getting an accurate diagnosis is important in order to get the right treatment for anyone, at any age, who is living with CSID.

But for babies, it is critical.

That’s because if they don’t gain enough weight as they are developing, they’re not getting all the important nutrients they need because their stomach can’t digest the foods they are eating if they have CSID. If left untreated, your child could end up with serious problems that may affect their growing brain and other organs.

School-Age Children

What’s happening. CSID is not always diagnosed during the infant and toddler years, possibly because parents limit the amount of “bad” sugars and starches that their child consumes. Or perhaps the symptoms are apparent but mild, such as diarrhea or other symptoms that aren’t that severe.

When that child is old enough to go off to school, parents have less control over their child’s food choices. They may begin eating “bad” sugar and starch, even when they believe they are making healthy choices. For example, they hear that bananas are good for you, but for someone with Sugar Intolerance, bananas are just one of many foods that has “bad” natural sugars in it.

Suddenly, your child’s once-mild symptoms are now severe. That’s when testing for CSID should be done.

What to look for. Typical symptoms of CSID in school-age children include:

  • Stomach pain and cramps or what your child may describe as frequent stomachaches
  • Gassiness or what they may describe as farting all the time
  • More frequent episodes of watery diarrhea
  • Not growing normally, not gaining enough weight


What’s happening. As any parent can tell you, the teen years can be a long struggle for independence. This is a time when kids have little interest in following any advice from mom and dad, let alone nutritional advice.

Teens who have not been diagnosed with CSID aren’t able to fully understand what’s causing their miserable symptoms. And because they’re embarrassed by the endless bathroom runs and noisy, stinky farts, they may not be quick to confide in anyone, including a parent or doctor.

Even teenagers who were diagnosed with Sugar Intolerance as children and who are well aware of their inability to process certain sugars and starch may resist advice from their doctor and parents.

Teens also have what seems to be a hard-wired urge to fit in with their friends, resulting in their making poor dietary choices. They rebel against the CSID-safe-eating rules because they want to eat the same things their friends are eating.

The good news is that a teenager is better able to tolerate small slip-ups than a younger child is. Their larger bodies have naturally developed a longer length of intestine, which helps to reduce symptoms.

But these stomach problems won’t go away. CSID can’t be outgrown because it’s genetic. It’s inherited from parents who are missing the genes, or DNA, needed to break down sugars found naturally in or added to a number of foods.

What to look for. Typical symptoms of CSID in teens include:

  • Looser than normal bowels
  • Bloating and gas
  • Watery diarrhea usually after eating sugary or starchy foods
  • Vomiting
  • Weight loss or the inability to get to a healthy weight


What’s happening. By adulthood, symptoms may ease as the intestines are now fully developed. However, an adult with CSID still has the condition and will still experience symptoms, which will be worse after eating foods with “unfriendly” sugars and starch.

What to look for. Typical adult symptoms are similar to CSID symptoms at younger ages:

  • Frequent pooping and chronic diarrhea, which lasts for a long time, or happens off and on but not go away completely
  • Stomach pain and gassiness
  • Bloating and a bulging belly
  • Weight loss
  • Nausea and vomiting

Don’t rely on “Dr. Google.” Here’s when to see a doctor to get your child properly diagnosed.

When to See a Doctor

With treatment available and info about foods to eat or avoid, a child with CSID can enjoy a happy and healthy life.

Sucrose Intolerance may be more common than you think.