FODMAP Explained: “O” Stands for Oligosaccharides

nuts have oligosaccharides.jpg

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”(including inulin, a longer chain of fructose molecules). 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.


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