Understanding the Digestive Struggle: Why Do I Struggle to Digest Carbs?

October 13, 2025 •

4 min read

According to research, a significant portion of the global population experiences some form of carbohydrate malabsorption, often mistaken for other issues. If you frequently ask, 'Why do I struggle to digest carbs?', understanding the root cause is the first step toward effective relief and better digestive health.

Quick Summary

Digestive issues with carbohydrates can stem from enzyme deficiencies like lactase, conditions such as SIBO, or sensitivity to FODMAPs. Symptoms including bloating, gas, and diarrhea are common, and personalized dietary adjustments can often provide relief.

Key Points

Enzyme Deficiencies: Lacking enzymes like lactase is a common cause of carbohydrate digestion problems, leading to specific intolerances like lactose intolerance.
FODMAPs Can Be Culprits: Many people struggle with fermentable short-chain carbohydrates (FODMAPs) found in a wide range of foods, which can be addressed with an elimination diet.
Gut Conditions Play a Role: Underlying health issues like SIBO, Celiac disease, or IBS can significantly impair carbohydrate digestion and absorption.
Diagnosis is Key: Rely on professional medical testing, such as hydrogen breath tests, to accurately pinpoint the specific carbohydrate(s) causing your digestive distress.
Solutions Are Personalized: Effective management involves identifying your unique triggers, which may include dietary changes, supplements, or treating underlying conditions.
Symptoms Are Your Guide: Pay attention to symptoms like gas, bloating, diarrhea, and abdominal pain after eating carbs, as they provide critical clues to the problem.

The Complex Journey of Carbohydrate Digestion

For most people, carbohydrate digestion is a seamless process. The body uses enzymes to break down complex sugars (disaccharides) and starches into simple sugars (monosaccharides), which are then absorbed by the small intestine. This process is crucial for providing energy. However, when this system falters, undigested carbohydrates proceed to the large intestine, where gut bacteria ferment them, producing gases and other compounds that cause discomfort. This fermentation leads to many of the hallmark symptoms of carbohydrate maldigestion, such as bloating, gas, and abdominal pain.

Common Reasons Behind Your Carbohydrate Struggle

Enzyme Deficiencies: When the Tools Are Missing

One of the most straightforward reasons for poor carbohydrate digestion is a lack of the necessary digestive enzymes. Lactase deficiency, more commonly known as lactose intolerance, is the most prevalent form of this issue worldwide, where the body fails to produce enough lactase to break down the milk sugar, lactose. Another, though rarer, condition is Congenital Sucrase-Isomaltase Deficiency (CSID), an inherited condition affecting the digestion of sucrose and some starches.

Gut Health and Digestive Disorders

Beyond simple enzyme issues, other conditions affecting the gastrointestinal tract can impair carbohydrate digestion.

Small Intestinal Bacterial Overgrowth (SIBO): An overgrowth of bacteria in the small intestine can ferment carbohydrates too early in the digestive process. This leads to excessive gas production and other irritable bowel syndrome (IBS)-like symptoms.
Inflammatory Bowel Diseases (IBD): Conditions like Crohn's disease and ulcerative colitis can cause inflammation and damage to the intestinal lining, interfering with the absorption of all nutrients, including carbohydrates.
Celiac Disease: In individuals with celiac disease, gluten exposure triggers an immune response that damages the small intestine's lining, leading to broad malabsorption issues.
Irritable Bowel Syndrome (IBS): While not a specific intolerance, many people with IBS have sensitivities to certain carbohydrates, which contribute to their symptoms.

The FODMAP Connection

FODMAPs are a group of short-chain carbohydrates that are poorly absorbed by the small intestine in many individuals. This group includes specific types of sugars, and their fermentation in the colon can cause significant distress. The low-FODMAP diet is a temporary elimination diet used to identify which of these carbohydrates might be a trigger for your symptoms.

Common High-FODMAP Foods

Fructose: Found in apples, watermelon, and high-fructose corn syrup.
Lactose: Present in milk, soft cheeses, and yogurt.
Fructans: Found in wheat, garlic, and onions.
Galactans: Found in legumes like beans and lentils.
Polyols: Found in sugar alcohols (sorbitol, xylitol) and certain fruits and vegetables like cauliflower and mushrooms.

Comparing Different Carbohydrate Intolerances


Feature	Lactose Intolerance	Fructose Malabsorption	General FODMAP Sensitivity
Primary Cause	Lack of the lactase enzyme	Limited capacity of intestinal fructose transporters	Poor absorption of various short-chain carbs
Trigger Foods	Dairy products like milk, soft cheese, and ice cream	High-fructose fruits, honey, and high-fructose corn syrup	Broad range of foods including certain fruits, vegetables, grains, and legumes
Diagnosis Method	Hydrogen breath test, lactose tolerance test	Hydrogen breath test	Elimination diet (low-FODMAP protocol)
Primary Treatment	Limiting or avoiding dairy, using lactase supplements	Reducing or balancing fructose intake, avoiding sorbitol	Phased elimination and reintroduction diet, guided by a dietitian

What to Do When You Struggle with Carbs

If you suspect an issue with carbohydrate digestion, the best course of action is to consult a healthcare professional, such as a gastroenterologist or a registered dietitian. Diagnosis often begins with a detailed dietary history and may involve breath tests, which measure the hydrogen and methane gases produced by bacterial fermentation. For example, a breath test after consuming a specific sugar solution can confirm lactose or fructose malabsorption. Genetic testing is also available for some congenital deficiencies.

Treatment is highly individualized and depends on the specific cause. For some, it may involve simply using an over-the-counter enzyme supplement like lactase. For others, especially those with broader sensitivities or IBS, a dietary approach like the low-FODMAP diet is recommended under professional guidance to identify triggers and create a sustainable, personalized plan. Addressing underlying conditions like SIBO or Celiac disease is also critical for long-term relief.

Conclusion

Struggling to digest carbs is a common issue with a variety of potential causes, from specific enzyme deficiencies like lactose intolerance to broader gut health problems like SIBO and IBS. Rather than completely avoiding all carbohydrates, which are a vital energy source, the key lies in identifying the specific triggers causing your discomfort. Through a combination of professional diagnosis and targeted dietary adjustments, it's possible to regain control over your digestive health and enjoy a wider variety of foods without pain and bloating. Seeking expert guidance is crucial to ensure you don't miss any underlying conditions and maintain a nutritionally balanced diet throughout the process.

Visit the Canadian Digestive Health Foundation to learn more about celiac disease and gluten sensitivities.

Frequently Asked Questions

Carbohydrate maldigestion refers to the inability to properly break down carbohydrates, typically due to an enzyme deficiency. Malabsorption is the inability of the body to absorb the broken-down sugars into the bloodstream. The terms are often used interchangeably, but maldigestion is the upstream cause of malabsorption.

The most common symptoms include gas, bloating, abdominal pain, cramping, and diarrhea, which occur when undigested carbohydrates are fermented by bacteria in the large intestine.

While gluten is a protein, many gluten-containing foods are also high in FODMAPs (fermentable carbohydrates). Breath tests can help distinguish between issues like fructose or lactose malabsorption and a true gluten-related issue like Celiac disease.

The low-FODMAP diet is an elimination diet that temporarily restricts foods high in certain fermentable carbohydrates. It is often highly effective for people with IBS or general carbohydrate sensitivities to identify their specific triggers.

Yes, for specific enzyme deficiencies like lactose intolerance, targeted enzyme supplements (e.g., lactase) can be very effective in helping the body break down the problem carbohydrate. Always consult a doctor before starting new supplements.

SIBO stands for Small Intestinal Bacterial Overgrowth. An overgrowth of bacteria in the small intestine can ferment carbohydrates prematurely, producing gas and causing symptoms like bloating and pain. It's a common cause of carbohydrate digestion problems.

No, it is not recommended to avoid all carbohydrates, as they are a vital energy source. Instead, focus on identifying your specific triggers through a proper diagnosis. Many people only react to specific types of carbohydrates and can tolerate others perfectly well.