Most people who want to learn more about nutrition do so because they don’t feel healthy.
They’re bloated, gassy, and lethargic.
Eventually, they come across the Paleo diet (this was me and you at one point), which appears to have all the answers.
For many people, adopting a Paleo diet is all they need to do to feel better and reduce their discomfort and flatulence.
Despite the number of positive cases, you still see questions like this from time to time about irritable bowel syndrome (IBS):
By the end of this article, you will know:
- What FODMAPs are
- The effects FODMAPs can have on your health
- Which foods contain FODMAPs
- and how a low-FODMAPs diet can work with Paleo
What are FODMAPs?
Carbohydrates consist of combinations of monosaccharide molecules, like glucose and fructose. For example, sucrose is made of one glucose molecule and one fructose molecule. Starches are more complex carbohydrates made of a large number of glucose molecules.
FODMAPs are specific carbohydrates that have small to medium chains (9 or fewer saccharides) that are difficult to digest. Note that not all short-chained carbohydrates are FODMAPs.
What is a Fermentable Carbohydrate?
The first letter in FODMAP stands for fermentable.
Most carbohydrates we ingest begin their break down in the saliva, and continue to do so as they pass through the digestive tract and reach the small intestine. They are broken down by enzymes, but each enzyme can only break down a specific type of saccharide bond.
There are certain foods, notably resistant starch and dietary fiber, that can’t be broken down by the enzymes in the upper gastrointestinal tract. Some carbohydrates can be broken down, just not by anyone. People who are lactose intolerant lack the enzyme lactase, which is made to digest the lactose sugar.
But your body doesn’t want to just waste these carbohydrates, and in many cases energy can be derived from them through bacterial fermentation. Your gut contains about 10 trillion bacterial cells, and they largely reside in the colon. Fermentation produces fatty acids that can be used by most cells for energy.
What Are Oligo-, Di-, Mono-saccharides, and Polyols?
Monosaccharides (‘one’-saccharide) are single sugar molecules like glucose, fructose, and galactose.
Disaccharides (‘two’-saccharides) consist of two monosaccharide molecules, like sucrose (table sugar).
Thirdly, oligosaccharides (‘few’-saccharides) have 3 to 9 saccharide molecules joined together.
Finally, polyols are a type of alcohol molecules. More specifically in regards to food, we’re concerned with sugar alcohols that are common food additives [link to food additives article], like xylitol and maltitol.
What are FODMAPs? – The Short Answer
There are three conditions that a carbohydrate must pass in order to be considered a FODMAP:
- Hard to absorb: FODMAPs cannot be easily digested and absorbed like other carbohydrates.
- Exerts a high osmotic force: Due to a combination of particle size and the degree of malabsorption, fermentable carbohydrates exert significant osmotic forces. This basically means that they these foods tend to draw a lot of water into the colon.
- Rapidly fermentable: Some carbohydrates ferment too slowly to cause problems. FODMAPs are short chain (under 9 monosaccharides) molecules that bacteria can quickly break down through fermentation.
There are a few types of food ingredients that are considered FODMAPs:
- Fructans: polymers that are hard to break down that contain fructose
- Galactans: polymers that are hard to break down that contain galactose (a monosaccharide)
- Lactose: a disaccharide found in milk
- Fructose: a monosaccharide found in fruits that can be difficult to absorb
- Sugar alcohols: sweeteners with fewer calories than sugar due to being difficult to absorb
What Foods Contain FODMAPs?
Since FODMAPs are carbohydrates, they are typically found in certain fruits and vegetables. Additionally, they are sometimes added to foods to improve taste.
Here is a chart that summarizes the foods that are highest in FODMAPs:
The above chart is not a complete chart. More research is still needed to determine all the foods that contain FODMAPs, as well as exactly how much is in each food. Additionally, as we’ll discuss later, not all FODMAP sources may be equally dangerous.
The Mystery of Irritable Bowel Syndrome
For all we do understand about inflammation and disease, there is still a lot that we don’t.
There are large gaps in our understanding of IBS. We still don’t know what causes IBS, despite it affecting about 10% of people at one time or another .
In case you’re unfamiliar with IBS, it’s the most common gastrointestinal disorder that has a wide variety of symptoms: diarrhea, bloating, abdominal pain, and flatulence. However, different people will exhibit different symptoms, and it’s often sudden.
We do know some of the triggers of IBS, like stress, large high-fat meals, and diseases like irritable bowel disease (related, but different) .
There’s one more trigger that you probably guessed: food.
By far the worst culprits appear to be foods that are high in FODMAPs.
Note that FODMAPs are not the cause of IBS, just a trigger. The underlying causes of IBS are unknown, but likely to be a combination of genetic and environmental .
How FODMAPs Trigger Irritable Bowel Syndrome (and more)
While there are many triggers of IBS, the most likely one with regards to FODMAPs is distension of the lumen of the small or large intestine. This means that the normal circumference of the small or large intestine becomes stretched due to the presence of solids, liquids, or gases.
This distension stimulates mechanoreceptors, which are biological sensors that detect pressure and volume change, which then trigger the common symptoms of the syndrome.
There are 2 ways that FODMAPs can cause intestinal distention:
- When carbohydrates are fermented by bacteria, they produce short-chain fatty acids, but also hydrogen or methane gas that bloat the gut .
- FODMAP particles also act as osmotic agents. This rapidly forces a large amount of water into the small intestine, which can lead to distension and diarrhea.
Who Do FODMAPs Affect?
If FODMAPs can cause gut distension, then why doesn’t everyone suffer from IBS after eating foods high in them?
Why do some people with lactose intolerance develop worse symptoms than others after consuming dairy?
There are two main differences in how people react to FODMAPs.
The first is that some people can break down and absorb certain FODMAPs better than others. For example, malabsorption of fructose or sorbitol only occur in certain people (about 30-50%), and occurs to significantly different degrees.
Some FODMAPs also trigger different symptoms. Fructose is likely to cause diarrhea, as it can cause the small intestine to swell with water. Another FODMAP, inulin, produces a lot of gas as it is fermented in the large intestine (colon), which will likely cause pressure and pain.
The second difference is that not all people are as sensitive as each other. People who experience IBS symptoms after consuming FODMAPs also usually have visceral hypersensitivity . This means that even a small amount of gastric distention can result in painful symptoms .
Why Don’t FODMAPs Cause IBS Flare-Ups All the Time?
In addition to the individual, there are also two factors about the FODMAP containing foods that we must consider.
Certain FODMAPs only cause issues in high doses, like xylitol. Others are fine when co-consumed with other specific nutrients. An example of this is when consuming fructose, if there is as much or more glucose compared to fructose present in the food, fructose is absorbed normally. However, if there is excess fructose, that’s when malabsorption is likely to occur.
The final factor is dose size. In general, the more of a FODMAP that you eat, the less you will absorb. Higher doses are also likely to cause more pain and other IBS symptoms.
The Low-FODMAPs Diet
If you’re healthy, FODMAPs are likely to cause no, or few, symptoms when eaten in normal doses. You don’t need to avoid them, and they will rarely (if ever) cause an issue for you.
However, if you have a history of IBS, a low-FODMAP diet is something you should at least try.
The low-FODMAPs diet has already shown to be more effective than the current standard nutritional advice for IBS sufferers.
There is a mountain of evidence that this approach works well to reduce IBS symptoms. The success rate of improving symptoms is approximately 75%. It’s recommended to try it out for 6-8 weeks to see if it’s effective.
There is no definitive low-FODMAP diet, just like there is no single Paleo diet. The general idea of a low-FODMAP diet is to limit your consumption of foods that are high in FODMAPs (in the chart from earlier).
Ideally, your food selection would be guided by a dietitian, but you can certainly test out the diet on your own to see if you notice any differences.
How do FODMAPs and Paleo Fit Together?
So now you know what FODMAPs are, what foods they are in, and why they are dangerous, as well as if you should try a low-FODMAP diet.
The final issue to address is how do FODMAP foods and Paleo foods interact.
If you follow the Paleo diet, you automatically cut out the wheat-containing foods, dairy, and foods with additives like fructose.
However, there are many fruits and vegetables that are Paleo, but still contain high levels of FODMAPs. In addition, sugar alcohols like xylitol are common sweeteners in Paleo treats.
If you suffer from IBS, even on a fairly strict Paleo diet, you are likely hypersensitive to intestinal distention. You should try to limit your FODMAP intake and see if your symptoms improve.
Here is a list of low-FODMAP Paleo fruits and vegetables that you include in your diet instead:
- Bok choy
- Green beans
- Green spring onions
- Maple syrup (as a sweetener)
Again, there are many foods that have not been tested for FODMAP content yet. If you have serious IBS issues, I suggest omitting any foods not on the above list and then testing them one-by-one.
To conclude, we know that avoiding FODMAPs can improve symptoms in a majority of functional gastrointestinal disorder sufferers. More research is needed into both the content of FODMAPs in food, as well as the effect of individual FODMAPs on different people.
Help us learn more about FODMAPs. Do you notice any particular foods that make your IBS symptoms worse or better? Let us know in the comments below!
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