Constipation & FODMAP connection

At no surprise, you may’ve heard that increasing fiber will help constipation sufferers.  But adding fiber doesn’t always boost stools.  In fact, you may experience more gas, bloating, and longer delays between stools.  

You may be wondering, do fibers not help constipation?  It’s true; fibers are great for constipation! But what you might not realize is, choosing the right type of “fiber” in the right dose might be the missing link.

To pick the right fiber for constipation, it’s important to know how the body digests and absorbs food, especially carbs, sugar, and fibers. 

Small intestine: Digestion and Absorption

Our small intestine is responsible for breaking down and absorbing nutrients from food. While, the colon is to absorb water and prepares undigested food to be removed from the body.  

The gut bacteria ferment undigested food as it passes through the colon. This results in the production of various substances. For instance, short-chain fatty acids(SCFA). It will also produce gasses such as methane and hydrogen. 

If you want to learn more about SCFA. Please check our discussion on the benefits of increasing SCFA with resistant starch on our blog, podcast & YouTube video “Constipation improves with a surprising starch.” 

After knowing some basics about digestion, absorption, and fermentation of undigested food, let’s discuss carbohydrates, which is where you find fiber.

Carbohydrates and Fiber

Fiber is an indigestible type of carbohydrate.  Uniquely, a majority of carbohydrates break down into glucose molecules, but fiber cannot and instead passes through the body undigested.

Categories of Carbohydrates

Technically, carbohydrates can be broken into two categories:

1. Simple
2. Complex 

Simple carbohydrates

The body breaks down simple carbohydrates quickly to produce energy.  In fact, various foods contain simple carbohydrates, such as fruits, sugar, refined grains.  

Complex carbohydrates 

The molecules of complex carbohydrates are linked together in long, complex chains. Whole grains, beans, peas, and vegetables are rich in complex carbohydrates. 

Simple carbohydrate breaks rapidly. Whereas, complex breaks at slower rate.  In addition, complex carbohydrates contain fiber. 

Now, let’s break down fiber a little more.

Fiber

Dietary fiber is a component of plant-derived foods that humans cannot fully digest. The body processes fibers differently based on their solubility, viscosity, and fermentability.

Technically there are three types of fiber

1. Soluble
2. Insoluble
3. Resistant starch

Soluble fiber

In water, soluble fiber can dissolve and form a gel. This type of fiber is found in plant cells. Gut bacteria ferment soluble fiber in the colon. Moreover, they produce short-chain fatty acids(SCFA) and gasses. Soluble fiber is found in beans, oats, fruits, and veggies. 

Insoluble fiber

Insoluble fiber absorbs water and swells up, giving bulk to your stool. This fiber makes up the structural part of plant cell walls. For instance, you can find insoluble fiber in the skins of fruits and vegetables, nuts, seeds, and whole grains.

Resistant starch

Resistant starch isn’t typically considered a “fiber,” but it resists normal digestion in the small intestines, acting similarly to soluble fiber with producing SCFA. 

So, let’s now jump to our main topic!

Constipation or diarrhea from fermentation

Carbohydrates and fibers have varying degrees of fermentability. The increased fermentation can affect transit time. That means food will move slower or faster through the gut. This can result in either constipation or diarrhea. When it comes to constipation or diarrhea, considering FODMAPs can be helpful.

What are FODMAPs?

These carbohydrates we’re discussing are known as FODMAPs. 

FODMAPs is the acronym for:

F=fermentable

O=oligosaccharides

D=disaccharides

M=monosaccharides

A=and

P=polyols

These are short-chain carbohydrates/sugars/fibers that can be poorly absorbed in the small intestine and fermented by bacteria in the colon.  

Some examples include:

Oligosaccharides: wheat, rye, onions, garlic, legumes, and lentils. 

Disaccharides: milk & milk products, 

Monosaccharides: cherries, grapes, honey, high fructose corn syrup, 

Polyols: apples, pears, artificial sweeteners, and foods that contain them

If you’d like to learn more about FODMAPs and bloating, check out my podcast “Why the FODMAP am I bloated?”

How do FODMAPs impact constipation?

We’re going to uncover the connection between certain carbohydrates and fibers naturally in food that can impact motility. 

For example, you may be miserable if you consume just 15 grams of fiber daily. This is where you have to appreciate dedicated researchers and clinicians. 

It wasn’t until researchers connected the dots between irritable bowel syndrome (IBS) and how certain foods triggered symptoms.  

For example, it was first believed that fatty foods, alcohol, gluten, and caffeine were responsible for IBS symptoms. 

However, the difficulty is everyone’s needs, and tolerance is different. 

When it comes to constipation, certain carbohydrate molecules have an osmotic effect. This just means more fluid is pulled into the colon. Consequently, gut bacteria rapidly ferment these molecules, producing gas in the process. 

The increase in both fluid and gas distends the bowel. Consequently, this may cause a sensation of bloating and abdominal pain, affecting how the muscles of the bowel wall contract. Some studies support the effectiveness of a low FODMAP diet in treating functional gastrointestinal symptoms.

A 2014 study in Gastroenterology found that reducing dietary FODMAPs, which restrict certain short-chain sugars and fibers, improved symptoms in IBS patients, including those with both diarrhea and constipation.

Moreover, studies have shown that low FODMAP diets may alleviate constipation-related pain and bloating.

While, a 2019 study found that FODMAP-rich foods increase symptoms of IBS and worsen them.

What foods are high in FODMAPs?

If you want to ease the symptoms of IBS and SIBO(small intestinal bacterial overgrowth), you should avoid high FODMAP foods, such as:

• Ice cream, yogurt, and milk derived from dairy products.
• Cereals, bread, and crackers made from wheat.
• Lentils and beans.
• Asparagus, garlic, onions, and artichokes are some of the vegetables.

How to choose the right fiber?

It’s import to work with a Registered Dietitian, like myself trained in FODMAPs.  Not every Dietitian understands how to implement an elimination diet.  With proper reintroduction. The good news is, it’s temporary.  A low FODMAP diet should never be followed long-term. 

How much fiber should you consume?

It depends.  Generally speaking, women should consume 25 grams of fiber a day, and men should consume 38 grams. However, depending on your symptoms, the amount may vary.  It depends on your tolerance. 

Consuming a high fiber diet is the ultimate goal.  Without digestive symptoms. 

Conclusion

A low FODMAP diet can improve bowel movements in patients.  Mainly from fermentation.  But FODMAP-rich foods also have their advantages. 

Therefore, working with a Registered Dietitian to remove & reintroduce FODMAPs is important.  The right fiber.  In the right dose.  At the right time improves motility and resolves constipation. 

I hope that makes you consider a different approach to exploring FODMAPs as a constipation treatment.