Carbohydrate Malabsorption or Intolerance – The Low-FODMAP Elimination Diet


In Article 6, you learned that Sucrose Intolerance may be more common than you think and could be causing or contributing to your unresolved IBS-D/M enteropathy symptoms of abdominal pain and/or discomfort, gas (abdominal bloating, distention, flatulence, and/or gurgling — rumbling), and bowel dysfunction including diarrhea. Eating commonly triggers these symptoms.

But another common differential diagnostic possibility is carbohydrate malabsorption or intolerance, which is the topic of this article.

Differential Diagnosis

Refer to Figure 7.1, which is a simplification of my map of Differential Diagnosis introduced as Figure 4.1 in Article 4.

Differential Diagnosis

Figure 7.1

The circled numbers have been removed with the exception of #6, which includes common, specific, food-related enteropathies. Recall learning in Article 5 that maldigestion and malabsorption are collectively referred to as malabsorption.

The red oval emphasizes considering the diagnosis of carbohydrate malabsorption of FODMAPs when the triad of symptoms of enteropathy is recognized. Remember, it’s possible for more than one diagnosis or disorder to be present, such as IBS (Article 3) and Sucrose Intolerance (Article 6).


So, what is this intimidating acronym? Here’s an “executive summary.”

FODMAPs stands for low “Fermentable Oligosaccharides, Disaccharides, Monosaccharides, And Polyols.” FODMAPs are carbohydrates — small sugars and fibers — found in many everyday foods. They are poorly digested, pull water into the gut (an osmotic effect), and are fermented by the gut microbes, which produces gas. Enteropathy symptoms result, particularly abdominal bloating, distention, and diarrhea.

FODMAPs are found in many healthy foods and don’t bother most people. However, in those with a sensitive gut and an enteropathy, such as IBS-D/M, FODMAPs can cause or contribute to enteropathy symptoms of abdominal pain and discomfort, gas, and diarrhea. It’s very common for meals to trigger symptoms 30 minutes to two hours or so after eating. While FODMAPs aren’t the cause of enteropathies and IBS, eating a low-FODMAP diet may be very helpful in relieving their symptoms.

The low-FODMAP diet is a novel, three-phase nutritional approach shown to be effective in managing symptoms in most IBS patients.

Common FODMAPs

FODMAPs are found in many foods of the Western diet: grains, fruits, vegetables, milk, and sugar-free additives. Specific examples include:

  • Fructose: fruits, honey, and high fructose corn syrup
  • Lactose: dairy products
  • Fructans (inulin): wheat, onion, and garlic
  • Galactans: beans, lentils, and legumes like soy
  • Polyols: sweeteners containing sorbitol, mannitol, xylitol, maltitol, and stone fruits, such as avocado, apricots, cherries, nectarines, peaches, and plums

Applying the Low-FODMAP Diet

Most individuals with IBS have heightened gut sensitivity known as visceral sensitization, so restricting FODMAPs can be effective in managing symptoms in 50% to 70% of patients. Furthermore, many with other enteropathies may also benefit by reducing or restricting FODMAPs.

The ultimate goal is to relieve symptoms and consume as liberal a diet as possible. There are three discrete phases to the low-FODMAP diet: elimination, reintroduction, and personalization.

1) Elimination Phase

All high FODMAPs foods are removed from the diet to determine if sensitivities to FODMAPs cause or contribute to symptoms.

2) Reintroduction Phase

FODMAPs are systematically added back into the diet by subtype (for example, fructose, lactose, fructans, galactans, and polyols) to identify FODMAPs triggers.

3) Personalization Phase

Tolerated foods containing FODMAPs are gently added back into the diet.

Who Can Benefit

The low-FODMAPs diet can be helpful in the following circumstances:

  • IBS has been diagnosed.
  • Food triggers symptoms.
  • A high-FODMAP containing diet is reported.
  • Celiac disease has been excluded.
  • Sucrose Intolerance has been excluded (refer to Article 6), since sucrose is not restricted in the low-FODMAP diet.

Who Wouldn’t Benefit

The low-FODMAP may not be appropriate in the following circumstances:

  • Eating doesn’t trigger symptoms.
  • There’s a history of eating disorder, maladaptive eating, or extreme food fears.
  • High-FODMAP foods haven’t been found to be a problem.
  • FODMAPs restriction hasn’t helped.

What the Low-FODMAP Diet Isn’t

There are many common misconceptions about the diet.

It’s not dairy, gluten, or wheat free.

Certain low-lactose dairy products are included, such as hard and semi-soft cheeses, butter, lactose-free milk, lactose-free yogurt, and lactose-free cottage cheese. Gluten — a protein — is reduced, by minimizing foods containing wheat, barley, or rye.

It’s not a low-fiber diet.

Most people don’t ingest adequate fiber. The low-FODMAP diet includes fiber-rich options, such as oats, oat bran, strawberries, blueberries, kiwifruit, baked potato with skin, quinoa, buckwheat, chia, and hemp seeds.

It’ not a low-carbohydrate diet.

While low-carbohydrate diets have become quite popular, the low-FODMAP diet includes adequate carbohydrates to provide energy needs, including rice, gluten-free pasta, baked potato, low-FODMAP fruits, and most gluten-free grains.

Benefits of Working with a Gastrointestinal (GI) Dietitian

It’s usually best to work with a registered dietitian who has GI expertise in the low-FODMAP diet, since there is some complexity to the three-phase regimen. As noted in the previous section, it’s initially an elimination diet not intended to be applied indefinitely. The goal is to manage symptoms by consuming as liberal a diet as possible to meet nutritional needs.

GI dietitians provide personalized nutritional advice and guidance in the low-FODMAP diet. Self-guided elimination diets may result in severe food restriction and in some cases, malnutrition.

Unfortunately, there’s a shortage of these GI registered dietitians.

The views, opinions, and positions expressed by the authors and those providing comments on these blogs are theirs alone and do not necessarily reflect the views, opinions, or positions of

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