FODMAP Explained: “O” Stands For Oligosaccharides

Welcome back to my “FODMAP Explained” Series! This is a set of articles dedicated to explaining the acronym FODMAP and giving practical tips to avoid symptoms while including as wide a variety of foods as possible.


The “O” in FODMAP stands for “Oligosaccharides”. These are short-chain carbohydrates (or sugars) – in Greek oligos means “a few” and saccharide means sugar – that can have 3 to 10 single sugar units. In contrast, polysaccharides are long-chain carbohydrates – poly means “many” – that have more than 10 sugar units.

Greek aside, what is important to remember is that we cannot digest these molecules as they are but need to break them down to their single sugar units (glucose, fructose or galactose). Humans, unfortunately, don’t have the enzymes that are able to accomplish that task, and these carbohydrates move through the GI tract undigested. When they reach the large intestine, they meet our good bacteria. And - you probably guessed it - they do have those enzymes that break down the bonds between sugar units and use them for energy (their fast food!). Whereas healthy people only have a bit of gas as part of this normal digestive process, people with IBS have a hypersensitive gut and this fermentation process leads to excess gas, bloating, abdominal pain and perhaps altered motility (constipation or diarrhea).

The two main Oligosaccharides

There are two main oligosaccharides in our diet: galacto-oligosaccharides (GOS) and fructo-oligosaccharides (FOS), or “fructans”. The foods that contain a high amount of these FODMAPs are avoided or limited during the elimination phase of the low FODMAP diet. Some examples are:

Galacto-oligosaccharides (GOS)

  • Nuts (cashews, pistachios, high amounts of other nuts)

  • Legumes (butter beans, red/green lentils, chickpeas)

  • Some vegetables (peas, butternut squash)

Fructo-oligosaccharides (FOS)

  • Grains and cereals (wheat bread and pasta, couscous, amaranth)

  • Some vegetables (garlic, onions, artichokes, Brussels sprouts)

  • Some fruits (dried fruit, persimmon, grapefruit)

  • Some beverages (strong black tea, chamomile tea, kombucha)

To complicate things, some foods have both GOS and FOS: black beans, cashews, barley and beets, just to name a few.

Bottom line: what can you eat?

If you have IBS and are trying to alleviate your symptoms, you shouldn’t avoid FOS and GOS altogether as they can have beneficial effects. They act as prebiotics, that is, they encourage the growth of good bacteria, and are rich in fiber and many nutrients. Here are a few tips:

  1. While on the elimination phase of the diet, avoid the foods that have the highest amounts of FOS and GOS (see some examples above and check out more on the Monash University low FODMAP Diet App).

  2. Have small amounts of some nuts (almonds, hazelnuts), seeds (chia seeds, sunflower seeds), and canned chickpeas or lentils (they are lower in FODMAP than their dried and boiled counterparts). Try my Silk Road Spiced Nuts recipe below.

  3. Choose gluten-free grains such as brown rice, millet, quinoa and corn tortillas.

  4. Eat small amounts of fruits (a ½ cup per meal or snack is a good rule of thumb) but no dried fruits.

  5. Eat mostly low FODMAP vegetables and load up on those that have only trace amounts or none at all (some examples are kale, carrots and red bell peppers).

  6. Drink weakly brewed black tea or herbal teas such as ginger and peppermint (these are all great to soothe a tummy ache).

 Most important of all, stay on the elimination phase of the low FODMAP diet as little as possible, until your symptoms have mostly subsided. Then move on to the re-challenge phase with the help of an expert dietitian who can guide you and help you find out which food you can safely re-introduce into your diet. At the end of this process, most people find they can reintroduce many of these foods and enjoy a more nutritious and varied diet.

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Silk Road Spiced Nuts


2 Tablespoons lemon juice

1 Tablespoon avocado oil

¼ teaspoon sea salt

½ teaspoon ground cumin

½ teaspoon ground coriander

¼ teaspoon cayenne or paprika (optional)

1 cup walnuts, pecans, or almonds


1.     Preheat the oven to 350°F. Line a rimmed baking sheet with parchment paper.

2.     Put the lemon juice, oil, salt and spices in a small bowl and whisk to combine. Add the nuts, and toss until evenly coated. Spread the mixture evenly on the baking sheet.

3.     Bake for 10-15 minutes, until the nuts are aromatic and slightly browned. Let cool to room temperature, then use a metal spatula to loosen the mixture.

Chef’s note: as soon as you start to smell the aroma wafting from the oven, it’s time to remove the nuts. The will continue to cook as they cool.


8 servings, about 2 Tablespoons each


Store in an airtight container in the refrigerator for up to 5 days.


Adapted from The Longevity Kitchen, by Rebecca Katz


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

A few chocolate shavings or 2-3 raspberries per serving to top (optional)


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 top with a small amount of shaved chocolate or 2-3 raspberries per serving, if desired.

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