Prebiotics and IBS

bowl of white rice
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Science is increasingly recognizing the importance of prebiotics for gut health. However, many prebiotics are fermentable and thus can serve to worsen IBS symptoms. If you have IBS, you can see that you are thus caught in a Catch-22 - if you eat foods containing prebiotics, your symptoms may worsen, but if you avoid prebiotics, you may never improve the bacterial balance within your gut that could help to resolve your IBS.

Let's take a look at prebiotics and IBS to see if there is a way out of this "rock and hard place" scenario.

What Are Prebiotics?

Prebiotics are components of foods that are not able to be digested and through their interaction with gut bacteria are thought to be health-promoting.

Prebiotics are not digested in the small intestine because we lack the enzymes necessary to break them down into components where they can be absorbed into our bloodstreams. This lack of breakdown brings them into contact with gut bacteria, where they play a role in stimulating the growth and activity of select bacteria that are good for our health. Much of this beneficial interaction with gut bacteria is due to fermentation.

Prebiotics are most likely to increase the number of bifidobacteria (a friendly type of bacteria often targeted by probiotic supplements), but also appear to increase the amount of various other host-friendly bacteria.

As you look at the list of commonly consumed prebiotics, you will see terms recognizable from the carbohydrates identified as troublesome for IBS by the low-FODMAP diet researchers:

  • Fructans (inulin and fructooligosaccharides)
  • Galacto-oligosaccharides (GOS)
  • Oligofructose (fructose)
  • Resistant starch

Prebiotic Containing Foods

Because many FODMAPs are prebiotics, you will see a lot of high FODMAP foods on this list:

  • Asparagus
  • Chicory root
  • Fennel
  • Garlic
  • Jerusalem artichoke
  • Legumes (beans, chickpeas, lentils, soybeans)
  • Nuts such as cashews and pistachios
  • Onions, leeks, shallots, scallions
  • Wheat products, such as cereal

Prebiotics for IBS

Some studies have been conducted to see if increasing prebiotic intake can be of help in reducing IBS symptoms. Results have been very mixed, but it does appear that higher amounts of prebiotics resulted in worsening symptoms for study participants - not surprising given what we know about FODMAPs effect on IBS symptoms (more fermentation leads to increased gas which results in gassiness, bloating and abdominal pain).

I was able to find one preliminary study on the effectiveness of a prebiotic supplement for IBS. The number of participants in the study was quite small so we cannot draw any firm conclusions from this trial, other than the fact that such a study opens up the door to the possibility that in the future we will see IBS-friendly prebiotic formulations come on the market.

How to Safely Get Your Prebiotics In If You Have IBS

Prebiotic-containing foods are something you may want to be eating more of - for your health and for your IBS. But how to do that without worsening your IBS symptoms? Here are some ideas:

1. Slowly increase your intake of low-FODMAP foods that contain resistant starch. Resistant starch has prebiotic qualities but at lower levels of fermentation. Here are some examples of foods that are both low in FODMAP yet contain higher amounts of resistant starch:

  • Bananas, the less ripe the better.
  • Plantains
  • Potatoes (raw is optimal, although perhaps not as palatable!)
  • White rice

2. Try following the low-FODMAP diet for a period of two to six weeks. Once you have been through the elimination period and are optimally experiencing significant symptom relief, you can slowly start to re-introduce foods that are listed above as being high in prebiotics. You may find that you are able to tolerate some of these foods without exacerbating your symptoms. The ultimate goal is to eat as many of these foods as you can while still remaining symptom-free.

3. Keep in mind that not all foods that are ferment-able might be a problem for you. Through trial and error you may be able to find some foods that you are able to tolerate without experiencing worsening symptoms.


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Silk, D., "Clinical trial: the effects of a trans-galactooligosaccharide prebiotic on faecal microbiota and symptoms in irritable bowel syndrome" Alimentary Pharmacology & Therapeutics 2009 29:508–518.

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