Carbohydrate Intolerance in Babies: A Common Cause of Diarrhea
By Rowena Bennett, RN, RM, CHN, MHN, IBCLC • Updated January 2026
If your baby suddenly develops diarrhea but otherwise seems well, the cause may be difficulty digesting certain sugars found in foods and drinks. This is known as carbohydrate intolerance and is a common reason for loose, watery stools in babies.
Understanding which foods are more likely to trigger symptoms, why this happens, and what simple steps you can take can help you manage your baby’s symptoms and avoid unnecessary dietary restrictions.
- Carbohydrate intolerance is a common cause of sudden diarrhea in otherwise healthy babies.
- Symptoms often occur after foods or drinks containing certain sugars.
- Fruit juices, sweetened drinks, and some fruits are common triggers.
- This condition is usually temporary and improves with dietary adjustment.
- Carbohydrate intolerance is different from food allergy and does not involve the immune system.
What is carbohydrate malabsorbtion?
Carbohydrates are the sugars and starches found in milk, foods (including juices) and some medications.
In order for the body to be able to absorb carbohydrates onto the blood stream (to then be used for energy) they need to first be digested (i.e. broken down into simpler sugars) by the relevant digestive enzymes. These include lactase, maltase, isomaltase, and sucrase.
When there is an insufficient amount of one or more of these enzymes, or when the diet contains carbohydrates that are difficult to digest, some carbohydrates pass through the digestive system without being properly absorbed. This is known as carbohydrate malabsorption and can lead to gastrointestinal symptoms such as diarrhea, gas, and abdominal discomfort.
What foods can cause problems?
While the only carbohydrate in breast-milk is lactose, formula or starting solids introduces various other carbohydrates such as fructose, sorbitol, sucrose and starches.
Fruit juices containing sorbitol or a high ratio of fructose-to-glucose (prune, apple and pear juice) can result in chronic diarrhea, flatulence, bloating, and abdominal pain in some infants and children.
| FRUIT | FRUCTOSE | GLUCOSE | SUCROSE | SORBITOL |
| Prune | 14.0 | 2.3 | 0.6 | 12.7 |
| Pear | 6.6 | 1.7 | 1.7 | 2.1 |
| Apple | 6.0 | 2.3 | 2.5 | 0.5 |
| Orange | 2.4 | 2.4 | 4.7 | 0 |
| Grape | 6.5 | 6.7 | 0 | trace |
| Pineapple | 1.4 | 2.3 | 7.9 | 0 |
| Peach | 1.1 | 1 | 1.7 | 0.9 |
* Values shown are approximate and provided for comparison only. Sugar content varies by fruit variety and ripeness. Fruits higher in fructose and sorbitol are more likely to trigger symptoms in babies with carbohydrate intolerance.
Eating whole fruits does not cause the same intensity of gastric symptoms because the fiber contained in the fruit (but removed from fruit juice) slows down the digestive process allowing more time for adequate digestion and absorption of the sugars.
Malabsorption of sugars and starches found in some foods can also result in gastric symptoms. These foods include sugars such as raffinose in beans; fructose in onions, artichokes, pears and wheat; sorbitol in fruits such as apples, pears, peaches, and prunes; and starches found in potatoes, corn, noodles, oats and wheat.
NOTE: Although lactose intolerance is also a carbohydrate malabsorption disorder, information on this condition is covered more comprehensively in a separate article.
Signs and symptoms
If a carbohydrate (sugar or starch) is not adequately digested, this means that it will continue to pass though the intestines (rather than be absorbed into the blood stream, as it would if it were digested). Once it reaches the large bowel, it draws in extra fluid into the bowel by a process called osmosis. The bacteria normally present in the bowel, ferment the undigested carbohydrates and as a result gastric symptoms may develop. The symptoms include:
- watery diarrhea;
- abdominal distension or bloating;
- cramps;
- excessive gas.
Fruit juices containing sorbitol (an alcoholic sugar found in many fruits) may be associated with carbohydrate malabsorption without typical gastric symptoms. Rather the symptoms may include...
- Increased physical activity and irritability
NOTE: The malabsorption of carbohydrates that can result from large intakes of juice is the basis for some health care providers to recommend juice for the treatment of constipation.
Why juice can cause diarrhea in babies
Fruit juices contain high amounts of certain sugars, particularly fructose and sorbitol, which can be difficult for babies to digest. When these sugars are not fully absorbed in the small intestine, they pass into the large intestine where they draw in water and are fermented by gut bacteria. This process can result in loose, watery stools, gas, and abdominal discomfort.
Babies are especially prone to this because their digestive enzymes and intestinal transport systems are still developing. Even small amounts of juice, including diluted juice, can exceed a baby’s ability to absorb these sugars.
Juice is also low in fat and protein, which normally slow digestion. As a result, sugary fluids move quickly through the gut, increasing the likelihood of diarrhea.
For this reason, fruit juice is a common cause of diarrhea in babies and young children who otherwise appear healthy.
Who is affected?
Carbohydrate malabsorption is common in infants and young children as their capacity to absorb some sugars and starches is more limited than an adult's.
Carbohydrate malabsorption (often referred to as intolerance) is particularly common in infants younger than 3 months of age due to an immature digestive system and an incomplete development of their intestinal flora.
What you can do to help
- Avoid introducing solid foods before your baby shows signs of readiness.
- Avoid offering fruit juice to babies, especially juices high in fructose or sorbitol.
- If juice is already being offered, stop it for a period and offer water instead.
- If juice is given to older infants or toddlers, dilute it by at least 50% and keep amounts small.
- Be mindful that some fruits (such as pear and prune) are more likely to cause loose stools.
By Rowena Bennett
About Rowena
Rowena Bennett (RN, RM, CHN, MHN, IBCLC) is a leading infant-feeding and sleep specialist and author of several books on infant feeding, sleep and behaviour, including the widely acclaimed “Your Baby’s Bottle-Feeding Aversion: Reasons & Solutions" and "Your Sleepless Baby: The Rescue Guide". With over three decades of clinical experience across child health, midwifery, mental health, and lactation, she has helped thousands of families worldwide understand and resolve complex feeding challenges through her evidence-based, baby-led approaches.