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Reviewed by: HU Medical Review Board | Last reviewed: May 2024 | Last updated: May 2024

While experts are unsure of the underlying cause of IBS, some believe it is a combination of several factors. These factors include:1,2

  • Bacterial overgrowth
  • Microscopic inflammation
  • Hypersensitivity
  • Alterations in gut motility (movement of the muscles in the intestinal tract)

In order for our gut to function properly, we need a specific balance of “good” bacteria living in our gastrointestinal tract. These bacteria:3,4

  • Help boost our immune system
  • Aid in nutrient and drug processing
  • Play a role in maintaining the function of our intestinal barriers

Some experts believe that a disruption in the normal human gut-bacteria relationship may contribute to the development and symptoms of IBS. Several studies have shown that people with IBS may have fewer numbers 2 health-promoting bacterial organisms called lactobacilli and bifidobacteria.1,4,5

What are prebiotics?

Along with using IBS-specific medications, some people may also try alternative or complementary therapies to control their symptoms. Common alternative therapies for IBS are probiotics and prebiotics. Probiotics are supplements that contain “good” bacteria, like lactobacilli and bifidobacteria species. These supplements deliver health-promoting bacteria directly to the gastrointestinal system.1

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Prebiotics, on the other hand, can be described as the food source for these bacteria. Prebiotics can be taken as supplements or can be obtained from some of the foods we eat. They are fermentable and non-digestible by the human body. This means they can be used by our health-promoting gut bacteria to enhance growth and activity.1,2,6

Commonly used and discussed prebiotics include:1,2,6

  • Oligofructose
  • Fructans (inulin and fructooligosaccharides)
  • Galactooligosaccharides
  • Resistant starch

These are all carbohydrates that the human body can’t break down but bacteria can. When prebiotics and probiotics are combined, they are called synbiotics.1,2,6

Research on prebiotics in the treatment of IBS

Like many complementary and alternative therapies, there is no strong scientific consensus on the effectiveness of prebiotics in treating IBS or its symptoms. Studies that have been completed thus far have provided mixed results. There is much more research on probiotics and their potential health benefits than research on prebiotics or synbiotics. Some studies have found that prebiotics may have no effect on IBS symptoms or may even worsen symptoms for some people.1

Results from other studies have found that some symptoms may improve with prebiotic therapy while other symptoms may be unchanged or worsen at the same time. Symptom changes or improvements may vary based on the type of prebiotic taken and the dosage. For example, lower doses of prebiotics may reduce symptoms like gas and bloating, but high doses may worsen symptoms.1,5

One study on mice suggested that taking prebiotics before IBS develops may prevent the onset of the condition in the first place. However, research is needed to understand this connection.4

While more researchers are now studying our gut bacteria and their relationship to our overall health, data on prebiotics and synbiotics is lacking and mixed at this time. Much more research is still needed to determine the relationship between prebiotics and IBS symptom management. 2

Sources of prebiotics

Prebiotics can be taken in supplement form or can be obtained in foods that we eat. Examples of foods that contain prebiotics may include:6,7

  • Oatmeal
  • Whole grains
  • Bananas
  • Artichokes
  • Asparagus
  • Onions
  • Fennel
  • Garlic
  • Legumes (beans, lentils, chickpeas)
  • Cashews
  • Pistachios
  • Chicory root
  • Shallots

When considering prebiotics

It is important to note that prebiotics are FODMAPs, which may be restricted in people following a low FODMAP diet to help improve symptoms. However, long-term low FODMAP diets may not be recommended for people with IBS. Talk to your doctor or a nutritionist before trying any new dietary changes or supplements.8

Supplements are not regulated by the US Food and Drug Administration (FDA) the same way other drugs are. This means that no outside agency confirms the ingredients or suggested dose. Many more supplements are sold than are tested. Your doctor can help you decide if a supplement is safe.9

Other treatment options

Along with prebiotics, there are other complementary and alternative treatment options that may be utilized by individuals with IBS alongside a traditional, FDA-approved medication regimen. These include probiotics, exercising, and increasing fiber intake or making other dietary changes. Some trial and error may be required to find the best balance for you.

Before beginning treatment for IBS, tell your doctor about all your health conditions and any other drugs, vitamins, or supplements you take. This includes over-the-counter drugs.

Treatment results and side effects can vary from person to person. This treatment information is not meant to replace professional medical advice. Talk to your doctor about what to expect before starting and while taking any treatment.