Prebiotics: How To Keep Your Friendly Bacteria Happy on a Low FODMAP Diet

Published on: 06/12/2018

You may have heard that prebiotics are good for gut health. However, if you are on a low FODMAP diet you may find it difficult to eat enough prebiotic foods. Rest assured: you can have enough probiotics when eating low FODMAP. Let’s find out how you can do it, and why it’s important.

What are prebiotics and why you need them

Prebiotics are types of fiber that go undigested through the GI tract, are quickly fermented by the bacteria in our gut, and stimulate their growth and activity. You can think of them as your friendly gut bacteria’s favorite food.  Indeed, we want to keep feeding these friendly gut bacteria because they confer a number of health benefits. Here are some of the things they can do for us:

  • They are like an army defending us from the harmful (disease-causing) bacteria – the higher the number, the less space there will be for the bad bacteria to find a place to reside.
  • They can produce vitamins (several B vitamins including vitamin B12, as well as vitamin K) and even amino acids.
  • The by-products of their fermentation confer health benefits: we know from research that the short-chain-fatty-acids (SCFAs) they produce can help protect us from colon cancer.
  • They may have several more health benefits that are currently being studied. For example, they may help us improve our immune system and fight obesity.

The downside is that, as bacteria feast on this food, they also produce gas. In healthy people, this is no more than a “nuisance”. However, in people with IBS, the gas may be excessive, painful, and life-disrupting. 

Getting enough prebiotics on a low FODMAP diet

The low FODMAP diet minimizes the intake of prebiotics to reduce IBS symptoms. As such, it reduces the amount of food available to the friendly bacteria in our gut, potentially “starving” them. Indeed, studies that have looked at the impact of a low FODMAP diet on gut bacteria have shown that after only 3 or 4 weeks of the elimination phase, both the amount and variety of good bacteria are decreased. One study also showed that there was an increase in bad bacteria.

Should you be worried? Yes and no. For starters, no one should be in the elimination phase for more than 4-6 weeks. At the same time, while you are in that strict phase, you shouldn’t completely eliminate all prebiotic-rich foods but just minimize them. You can eat small portions of these foods and keep your gut bacteria from “starving”. 

Low FODMAP prebiotic foods

Here are a few examples of foods that confer some prebiotics but are low FODMAP (at the “green” serving size, according to the Monash Low FODMAP Diet App): 

  • Vegetables: potatoes (cooked and cooled as in a potato salad), butternut squash, cabbage, eggplant, fennel
  • Fruit: green or firm bananas, kiwi, grapefruit, pomegranate seeds
  • Whole grains: raw rolled oats; buckwheat groats, brown rice, and quinoa, cooked and cooled, as in a grain salad
  • Legumes: canned chickpeas and lentils
  • Nuts: almonds, hazelnuts

Final thought

In sum, it is definitely possible to include enough prebiotic foods and keep your gut bacteria well-fed and happy even on a low FODMAP diet.

Furthermore, once you start reintroducing high-FODMAP foods, you may find that you can bring back more prebiotic-rich foods into your diet. The goal is to find a good balance between keeping symptoms at bay and eating some prebiotic-rich foods to achieve the right equilibrium of gut bacteria. The good news from research in this field is that, once people start eating more prebiotics, the gut population grows back strong!

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I’m a registered dietitian with a passion for helping women with IBS find their way back to eating without fear of painful gut symptoms and without unnecessary diet restrictions.

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