What is the best fiber for constipation: Three factors - Solubility, Viscosity, Fermentability. Will a Floura bar help?

Floura Bar is one of the latest fiber bars on the market. This is what you get when you open the "variety pack" box. I like the emphasis on the "fiber gap" (more on that in another post).  

Let's first break down what is meant by "improved regularity". Generally, that means having bowel movements that are consistent in frequency and consistency.

• Frequency varies from person to person and, generally, can range from 3 bowel movements a day to 3 bowel movements a week.
• Normal consistency is generally a Bristol Type 4 (see figure). 

Figure 1. Bristol Stool Scale

Say you are struggling with constipation (having less than 3 bowel movements a week and/or Bristol 1-3, symptoms of incomplete emptying, straining, etc.).

Will a Floura bar help you?

The best test would be a randomized placebo controlled blinded study. It would not be fair to expect that level of scrutiny out a fiber bar. However we can help predict a laxative effect by looking at the ingredient list. We all know that we generally we do not get enough fiber in our diet and more fiber is good, but not all fiber is created equal when it comes to a laxative effect. 

Generally I look for dietary fiber that is soluble, non-fermentable, and viscous. This is dietary fiber that dissolves in water, forms a gel-like consistency, and is not broken down by bacteria in the gut, meaning it does not ferment significantly. This leads to water retention, increased stool volume, and potential improvement with peristalsis (Chutkan 2012). 

Insoluble fibers, such as wheat bran may also lead to a laxative effect through a mechanical stimulatory effect on gut mucosa. However, "insoluble fiber will only have a significant laxative benefit if consumed as large, coarse particles. Finely ground insoluble fiber (e.g., whole wheat flour) loses this laxative benefit". 

A common soluble, non-viscous, and readily fermentable fiber is inulin. I see this in Olipop, Metamucil gummies...basically most fiber brands that makes a claim for regularity that do not readily form a gel. As expected, aside from the paper I found below, there is little evidence comparing different types of fibers and assessing effect on bowel movements (what money is there to be made on that?).

This study from 2022 assessed the effects of different fibers on the microbiome including a comparision of arabinoxylan (AX, common in whole grains and the hemicellulose of other plants and found in a high amount in psyllium husk) to long chain inulin (LCI). Stool consistency as measured by increase in Bristol stool score improved in a statistically significant manner (p < 0.05) compared to no change for LCI (Figure 2). There were also larger effect sizes for AX compared to LCI for stool frequency increase over time, and stool volume increase. Important to note that there was a statistically significant increase in bloating with LCI compared to AX, as well as increase in flatulence with both fibers but greater effect size with LCI. This supports the claim that inulin is readily fermentable, as above. 

 

 

Figure 2.  From supplementary section of 2022 paper by Lancaster et al. Note the red line (AX, commonly found in psyllium husk) compared to the blue line (inulin). 

In the management of chronic idiopathic constipation, the 2 major GI societies (ACG and AGA) recommend using fiber such as bran, inulin, and psyllium. 

*The author of the above citation and other articles written about the laxative effects of soluble, non-fermentable, and viscous fiber is Johnson W. McRorie, Jr, PhD, who is a full-time employee of the Procter & Gamble Company (who manufacturs Metamucil). That certainly can lead to bias in his claims. 

I also look for substances with an osmotic effect (that draw water into the colon and lead to softer stools) such as sorbitol. This is naturally found in fruit such as prunes, apples, and pears. Sorbitol is also commonly found in gum. In patients with chronic diarrhea, I always ask about potential use of sorbitol containing gum. 

OK Brambleberry Crip is my go to at a Jeni's ice cream shop. Now lets pick the Brambelberry Lavender Fruit Crush Bar and see if it could potentially improve constipation. 

We'll focus on if this product has any of the following substances. This is keeping in mind that we don't know exactly how much of each ingredient is in each bar and that the exact formulation is proprietary.

1. Soluble, non-fermentable, viscous fiber  
2. Soluble, fermentable, non-viscous  
3. Insoluble fiber  
4. Sorbitol 

1. Soluble, non-fermentable, viscous fiber -> Pectin, Floura SuperFiber Flour Mix?, white chia seeds.  

2. Soluble, fermentable, non-viscous -> Chicory Root Inulin 

3. Insoluble fiber - >  Pumpkin seeds, quinoa, watermelon rind, almond skins,  white chia seeds. 

4. Sorbitol -> Apple, watermelon rind. 

Can this product lead to improved bowel movements if you are having constipation? Unclear but I would say probably not. There is likely not enough soluble, non-fermentable viscous fiber. The amount of inulin (already not the best in terms of laxative effect) in 1 bar is likely not enough either. The insoluble fiber may or may not be large or coarse enough. Amount of sorbitol is unclear. 

If you are interested in trying any product for the purposes of improving constipation, I would recommend adding it to your daily routine and then keeping a stool diary.