Malabsorption and IBS

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If you have IBS, it is natural that you might be wondering if your "broken" bowels are actually absorbing nutrients from the foods that you are eating. You might be wondering that some long-term damage is being done to your body. Let's take a look at what is known about malabsorption and IBS in order to put some fears to rest.

What Does Malabsorption Mean?

In order to understand malabsorption, you need to know what absorption means in the context of digestion.

Absorption of nutrients from the food that we eat is the primary job of the digestive system. Some nutrients are absorbed by our stomachs, but most nutrients are absorbed by the small intestine. This includes the absorption of carbohydrates, fats, minerals, proteins, and vitamins. In order for nutrients to be absorbed, they need to be broken down into small enough particles to pass through into our bloodstreams.

Malabsorption, therefore, is a state in which nutrients are not absorbed by the small intestine as would normally be expected.

What Is Malabsorption Syndrome?

Malabsorption syndrome is a health condition in which the body has difficulty absorbing essential nutrients. This can lead to significant health problems as the body is not getting the nutrients, vitamins and minerals that it needs for optimal health.

Diseases that can cause malabsorption include:

Symptoms of Malabsorption

How would one know if you are not absorbing the nutrients that you need? Here are some symptoms:

  • Bloating and gas
  • Diarrhea
  • Failure to thrive (children)
  • Floating and/or greasy stools
  • Muscle loss
  • Weight loss

Malabsorption and IBS

Yes, some of the symptoms of malabsorption are the same as those of IBS. You will be relieved to know that it is not believed that IBS results in the malabsorption of any key nutrients. However, some malabsorption problems may be behind your IBS symptoms. In fact, the malabsorption of certain carbohydrates plays a large role in the thinking behind the low-FODMAP diet for IBS. It is theorized that because the carbohydrates are not absorbed at the level of the small intestine, they make their way into the large intestine, where they interact with gut bacteria, resulting in IBS symptoms. Let's take a look at some specific carbohydrates:

  1. FructoseFructose is a carbohydrate found in honey and many fruits. Our intake of fructose has increased dramatically with the inclusion of high fructose corn syrup in many convenience foods. It is estimated that one out of every three people has fructose malabsorption, meaning that they lack enough of the transport molecules needed to usher fructose into the bloodstream from the small intestine. If your IBS symptoms tend to worsen after consuming fructose, you may have a fructose malabsorption problem.
  1. Lactose: Lactose is the sugar found in milk products. People who have lactose intolerance do not have enough of the enzyme lactase in order to break down lactose for absorption in the small intestine.
  2. Sugar Alcohols: Sugar alcohols include the FODMAPs mannitol and sorbitol. Sugar alcohols are found in some fruits, vegetables, and artificial sweeteners. It is estimated that approximately 50% of people are unable to absorb sugar alcohols at the level of the small intestine.
  3. Fructans and galactans: Fructans are found in grains like wheat, and vegetables like onions and garlic. Galactans, sometimes called GOS, are found in legumes. These two groups of carbohydrates are an example of where malabsorption might be good for us. We all lack the enzymes necessary for absorbing these carbohydrates. It is thought that there are health benefits that come from that fact that these carbohydrates make their way into the large intestine and interact with our gut bacteria.

Bile Acid Malabsorption

This type of malabsorption differs from the ones we have discussed so far because the problem does not lie with the malabsorption of nutrients, but rather the malabsorption of bile acids. Bile acids are substances released from the gallbladder to aid in the breakdown of dietary fats. If a person has bile acid malabsorption, these acids are not well absorbed by the small intestine and thus enter into the large intestine. It is theorized that bile acid malabsorption may play a role in some cases of IBS-D:

What to Do if You Think You Have a Malabsorption Problem?

  1. Talk to your doctor! Your doctor is in the best position to assess your symptoms and their possible causes. If necessary, your doctor may send you for tests designed to assess the presence of a malabsorption problem.
  2. Keep a food diary. Writing down the foods that you eat and the symptoms that you experience can help you to look for patterns consistent with malabsorption.
  3. Try an elimination diet. If you or your doctor suspect a possible malabsorption to a particular type of carbohydrate, you could eliminate the possible culprit from your diet for a period of time and see what effects that has on your symptoms.


Barrett, J. & Gibson, P. "Clinical Ramifications of Malabsorption of Fructose and Other Short-Chain Carbohydrates" Practical Gastroenterology 2007 XXXI:51-65

"Malabsorption" Medline Plus Accessed June 26, 2015.

Minocha, A. & Adamec, C. (2011) The Encyclopedia of the Digestive System and Digestive Disorders (2nd Ed.) New York:Facts on File.

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