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

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 (think of them as their favorite food).  This is, in general, a good thing, as these friendly gut bacteria confer a number of health benefits.  For example, they keep at bay the “bad” bacteria, and can aid in the absorption of minerals and benefit the immune system. The downside is that, as bacteria feast on this food, they also produce gas. In healthy people this is no more than a “nuisance” but in people with IBS, the bacteria produce excess gas or flatulence, which can be painful and life-disrupting. 

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, leaving them potentially "starving".

Studies that have looked at the impact of a low FODMAP diet on gut bacteria have shown that after only 3 or 4 weeks on 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 starter, no-one should be in the elimination phase for more than 4-6 weeks. While you are in that strict phase you are not supposed to completely eliminate all probiotics but to minimize them. You can eat small portions of prebiotic-rich foods and keep your gut bacteria from "starving" too much. Here are a few examples of foods that confer some prebiotics but are still considered “low FODMAP” at the portion sizes specified:

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·      Vegetables: potatoes, savoy cabbage (1/2 cup), eggplant (1/2 cup), canned baby corn (up to 2 cups)

·      Fruit: green or firm bananas (1 medium), kiwi (2 small), pomegranate seeds (¼ cup)

·      Whole grains: rolled oats (1/2 cup), buckwheat groats (3/4 cup cooked), brown rice, and quinoa (1 cup cooked)

·      Legumes: canned chickpeas and lentils (1/2 cup)

·      Nuts: almonds and hazelnuts (10 each)

Finally, once you start re-introducing higher FODMAP foods, you may find that you can re-introduce some of the prebiotic fibers (oligosaccharides). The goal is to find a good balance between keeping symptoms at bay and eating some prebiotics 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!

5 Tips to Eat More Fiber on a Low FODMAP Diet

We all know fiber is a good thing. We keep reading articles about it in magazines and see packaged foods boasting "high fiber" claims in bold letters. Indeed, fiber has several health benefits: it helps our intestines function regularly and may help lowering cholesterol and blood sugar levels. 

People with IBS need to be careful about the amounts and types of fiber they eat so not to experience unwanted symptoms. Certain fibers are rapidly fermented in the large intestine and may lead to bloating, abdominal pain and excess gas. A few examples of foods that contain these types of fiber are onions, artichokes, wheat, and beans. These are the fibers a low FODMAP diet is designed to minimize.

Other types of fiber are slowly fermented and better tolerated, for example, the fiber in brown rice, kiwis, raspberries, carrots, and chia seeds.

How much fiber do we need? According to the Dietary Guidelines for Americans, and adequate fiber intake is 25 g per day for women and 38 g per day for men up to the age of 50 (a little less for older people). This is, however, for the general (healthy) population (sadly, most Americans consume too little fiber, an average of 15 g per day). Monash University recommends people with IBS eat between 25 and 30 g of fiber per day.

Here are 5 tips to eat more fiber:

1.     Don't be afraid to consume some fiber. Remember, this is a low FODMAP diet, now a zero FODMAP diet. On the other hand, don’t overdo it. Depending on your IBS subtype and symptoms (diarrhea or constipation), you might need to be on the low or high end of those recommendations. As you increase your fiber intake, make sure to also drink enough water during the day.

2.     Be sure to choose low FODMAP whole grains (brown rice, millet, quinoa) and don't limit yourself to the "white" stuff. There is a tendency for people to gravitate towards either avoiding grains altogether or mostly eat white rice, white-rice flour based products (crackers, gluten-free bread). By including more whole grains, in addition to the fiber (2-4 grams per cup of cooked brown rice, quinoa, quinoa-corn pasta or millet), you will get other important nutrients as well.

3.     Choose a variety of low FODMAP fruits and vegetables (keep the skin on) in small portions (1/2 cup is a good benchmark and will provide 2-4 grams of fiber) and spread them out throughout the day. Try some of these:

  • Fruit: raspberries, blueberries, strawberries, kiwifruit, oranges
  • Vegetables: carrots, radishes, kale, Swiss chard, eggplant

4.     Some canned legumes are ok even during the elimination phase (rinse and drain first). Try up to ½ cup per meal or snack (5-8 grams of fiber):

  • Lentils (great in soup, salads or chili)
  • Chickpeas (they are delicious roasted as a snack or sprinkled on salads)
  • Fresh or frozen edamame (boiled and rinsed)

5.     Don’t forget the nuts and seeds. In small amounts, these can contribute good amounts of fiber without triggering symptoms. Try up to 2 tablespoons per meal or snack (1-2 grams of fiber in most nuts/seeds; 10 grams in chia seeds):

  • Nuts: almonds or walnuts – great sprinkled on hot rice/quinoa cereal for breakfast
  • Seeds: pumpkin seeds (good by themselves or as topping for tacos) and chia seeds (in a smoothie or as chia pudding – see my recipe for Cocoa Chia Pudding below - who thought that eating more fiber could look like this?)

Finally, if you feel you need a fiber supplement, consult a dietitian before trying one on your own. If you choose the wrong fiber, you may make your symptoms worse. An expert dietitian can recommend one most suitable to your IBS subtype.

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Cocoa Chia Pudding


1 ½ cups unsweetened almond milk

¼ cup chia seeds

1 tablespoon unsweetened cocoa or raw cacao powder

1 packet powdered stevia (1 g)

1 teaspoon vanilla extract


1.     Combine the almond milk, chia seeds, cocoa, stevia, and vanilla extract in a bowl. Whisk until well combined and the mixture begins to thicken. Cover the bowl with plastic wrap and let sit in the refrigerator overnight or for 6-8 hours.

2.     When the pudding has set, give it one more stir, then portion into single-serve bowls. Alternatively, heat up in the microwave for a warm pudding.

3.     You can sprinkle a small amount of shaved chocolate or chips 

Yield: 2 servings

Storage: Store in the refrigerator in an airtight container for up to 4 days.

Author: Antonella Dewell, Registered Dietitian Nutritionist & Natural Chef

10 Ideas for Healthy Low FODMAP Snacks

For people with IBS, the ideal meal pattern is to consume 3 moderately-sized meals and 1-2 small snacks, preferably spaced 3-4 hours apart. One reason is that large meals may end up accumulating a large load of FODMAPs and trigger symptoms. This may happen even if you are careful and choose only low FODMAP foods, as people with IBS are very sensitive to the distention of the stomach wall and, when it enlarges due to a large amount of food, the nerves that surround it send signals of pain/cramping to the brain (this is called visceral hypersensitivity).

It’s best to avoid “grazing” or eating semi-continuously as this is similar to stacking too many FODMAPs in the same meal. The intestinal tract needs to be empty at intervals during the day so that it can benefit from what are called “migrating motor complexes”, healthy cleansing waves that occur in the small intestine when it is empty.

All this makes snacking play an important role in the Low FODMAP diet. Here are 10 ideas for healthy and nutritious low FODMAP snacks (most of them are portable and can be used when traveling):

1.   Vegetables: choose red/yellow/orange bell peppers, baby carrots, cucumbers and cherry tomatoes, either alone or with a dip or spread (see ideas below)

2.   Dips/spreads: home-made Baba Ganoush (no garlic) or lactose-free cream cheese

3.   A handful (about 2 tablespoons) of low FODMAP nuts (no pistachios or cashews) or an ounce of peanuts; they can be raw, roasted, salty, spicy or even chocolate-covered

4.   Two rice cakes or half of a firm banana with 1-2 tablespoons peanut butter or 1 tablespoon almond butter

5.   Fruit: 1 cup grapes or pineapple chunks, 2 small kiwis, 1 medium orange or 2 small mandarins

6.   Lactose-free plain yogurt, alone or with 1 ounce of blueberries or raspberries

7.   Hardboiled eggs sprinkled with salt & pepper or cayenne/paprika

8.   A pouch of water-packed tuna, alone, with raw vegetables (see above) or a handful of low FODMAP rice crackers

9.   Popcorn without added high FODMAP ingredients like garlic/onion powder or honey

10. Home-made roasted chickpeas (up to half a cup). See my recipe below: 

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Spiced Roasted Chickpeas


1, 15-oz can chickpeas, drained and rinsed

½ teaspoons freshly ground cumin*

½ teaspoon freshly ground coriander*

1 teaspoons paprika

¼ teaspoon salt

1 tablespoons avocado oil


1.     Preheat the oven to 425ºF. Line a baking sheet with parchment paper.

2.     Dry the chickpeas by spreading them on towels on your kitchen counter.

3.     In a large bowl, mix the cumin, coriander, paprika and salt with the oil, then toss the beans into the bowl and mix until they are well coated with the spices.

4.     Spread the chickpeas onto the baking sheet in one single layer and roast for 10 minutes. Shake the sheet and then bake for another 15-18 minutes, or until crispy.

5.     Use as a snack or a protein and fiber-rich topping for a salad.

*Note: for best flavor, roast the coriander and cumin seeds in a skillet until aromatic, stirring often and being careful they don’t burn. Transfer them to a coffee or nut grinder and grind them to a powder.

Yield: 4 servings

Storage: Store in an airtight container in the refrigerator for up to 4 days.

Author: Antonella Dewell, Registered Dietitian Nutritionist & Natural Chef