The FODMAP diet: everything you need to know
It may be key to helping relieve symptoms of IBS and SIBO.
What is the FODMAP diet?
You may have heard of the FODMAP diet before, and wondered what exactly it meant.
FODMAP is an acronym and stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols.
These super long words are terms for different types of carbohydrates (some of them simple sugars) that are prevalent in the diet. Just as some people can’t tolerate the milk sugar lactose, which is one of the disaccharides, others may not be able to tolerate inulin-type fructans or sugar alcohols, found in many sugar-free products.
The FODMAP diet eliminates these types of high-FODMAP foods, hoping to reduce gastrointestinal distress and improve symptoms in irritable bowel syndrome (IBS) such as pain, constipation, diarrhea, bloating, and flatulence.
FODMAPs - the carbohydrates (sugars) to avoid
The carbohydrates to avoid in high-FODMAP foods are specific types that may be poorly absorbed in the intestines, and foods that some people are more sensitive or reactive to.
When high-FODMAPs reach the intestines, the bacteria in your gut can begin to break them down (fermentation), which can cause flatulence and bloating. Some of the more simple sugars can be rapidly fermented by the gut bacteria in the upper GI tract due to their short chain nature, causing pain.
Let’s break it down:
- Fructooligosaccharides (FOS) also known as inulin-type fructans - found in chicory root (note: this is found in Pendulum Glucose Control, but in a very minimal amount), wheat, onion, and garlic
- Galacto-oligosaccharides (GOS) - found in beans, lentils, and legumes like soy
- Lactose - found in many dairy products. Fermented dairy like yogurt or kefir as well as hard cheeses (cheddar, gouda, parmesan, pecorino) do not contain as much lactose as regular cow's milk, this is because the bacteria culture has used most of the sugar during fermentation.
- Fructose - found in fruits, honey, and high-fructose corn syrup
- Sugar alcohols/sweeteners like sorbitol, mannitol, xylitol, maltitol, and stone fruits such as apricots, cherries, nectarines, plums, peaches, and avocados
The FODMAP diet protocol
The FODMAP diet protocol often follows a two-phased intervention (see below). That said, a lot of modifications of the protocol exist.
Eliminating some susceptible foods followed by a reintroduction is a good way to begin to test your sensitivity towards specific foods, but decreasing daily concentrations of for example inulin-type fructans (FOS’) may also result in overall gastrointestinal relief.
The big picture is to only eliminate foods that cause you distress - this will be different for everyone!
How it works:
Eliminate high FODMAPs from your diet for 4-6 weeks. Eliminating FODMAPs have shown the following changes in the gut microbiota:
- Decrease in Bifidobacteria: This is a group of bacteria associated with a healthy gut and therefore, the decrease observed is not ideal. This decrease has however shown to reverse itself 2 weeks after ending the FODMAP diet, see below) (reference).
- Increase in Bilophila wadsworthia: This is a bacterium associated with excess gas and intestinal inflammation (reference).
Slowly reintroduce some of the high FODMAPs back into your diet, according to tolerance. Be sure to keep track of what foods you don’t tolerate, and what foods you do tolerate!
Reintroducing FODMAPs have shown the following changes in the gut microbiota:
- Increase in Bifidobacteria
- The increase in Bilophila wadsworthia was shown to persist following discontinuation of the low FODMAP diet. This increase was also correlated with an increase in bloating frequency after diet intervention (reference).
Summarizing above, studies show that composition-changes in the gut microbiome driven by a low-FODMAP diet may persist after two weeks of stopping the diet, and this may cause IBS symptoms such as bloating.
Our pros and cons:
Pros: Short-term symptom improvement in IBS (may not be maintained long term due to potential changes in the gut microbiome profile). Many people experience a significant decrease in bloating within weeks.
Cons: The low FODMAP diet can be very extreme and restrictive as it limits many foods. A very restrictive diet is difficult to sustain.
With eliminating these foods, you may wonder, what can you have? Here are some foods to eat more of cited from Harvard University:
- Dairy: Lactose-free milk, rice milk, almond milk, coconut milk, lactose-free yogurt; hard cheeses such as feta and brie
- Fruit: Bananas, blueberries, cantaloupe, grapefruit, honeydew, kiwi, lemon, lime, oranges, and strawberries
- Vegetables: Bamboo shoots, bean sprouts, bok choy, carrots, chives, cucumbers, eggplant, ginger, lettuce, olives, parsnips, potatoes, spring onions, and turnips
- Protein: Beef, pork, chicken, fish, eggs, and tofu
- Nuts/seeds (limit to 10-15 each): Almonds, macadamia, peanuts, pine nuts, and walnuts
- Grain: Oat, oat bran, rice bran, gluten-free pasta, such as rice, corn, quinoa, white rice, corn flour, and quinoa
We also recommend this simple guide from the University of Wisconsin as a great reference.
The long-term implications of its effect on the gut microbiome are still to be determined, but studies have demonstrated a reduction in concentration and proportion of bifidobacteria (some of the very good ones) after 4 weeks of carbohydrate restriction (reference).
The oligosaccharides (FOS, GOS) are considered prebiotics that stimulate bifidobacteria in your gut, restricting these prebiotics in your diet may affect and change the composition of your gut microbiome in the colon.
If you are interested in knowing more about how high/low FODMAP diets alter the gut microbiome, colonic microenvironment, see here.
Talk with your doctor to see if the FODMAP diet is right for you!