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Using Konjac to treat Constipation

Constipation is often treated with laxatives. However, the frequent use of laxatives can cause negative side effects such as damage to cells. For this reason, it is definitely worth investigating alternative treatment.

Dietary fibre such as glucomannan has been shown to treat constipation by increasing stool bulk and promoting beneficial bacteria in the gut.

Study: Yang J, Wang H, Zhou L, et al. “Effect of dietary fiber on constipation: A meta analysis” [3]

This study analysed a collection of randomised trials on how the consumption of glucomannan can affect constipation. 1322 potential studies were searched, with 5 studies being included in the final analysis.

Results

Five trials found

  • glucomannan improved stool frequency

Four studies found

  • no significant difference in stool consistency between using placebo and using glucomannan

Conclusions

This meta-analysis shows that dietary fibre such as glucomannan can treat constipation by increasing the frequency of bowel movements.

This study also shows that there is no obvious correlation between an increased intake of dietary fibre and an improvement in stool consistency.

However, there are other conflicting factors that should be taken into consideration. For example, some studies involved a smaller number of patients. Different patients with constipation also have different levels of severity. Further studies that consider these factors should be undertaken in order to completely understand how dietary fibre can treat constipation.

Study: Chen H, Cheng H, Liu Y, et al. “Konjac acts as a natural laxative by increasing stool bulk and improving colonic ecology in healthy adults” [1]

This study investigated how glucomannan can treat constipation by promoting a healthy gut microbiome.

8 patients took part in this study.  During the study, all of the patients consumed 7 day cycle menus of low-fibre Chinese food.

During each meal, all patients consumed three gelatin capsules. Each capsule contained either

  • corn starch (placebo)
  • or glucomannan powder

The consumption of these capsules during the study is as follows:

For 21 days, the patients first consumed placebo capsules.

For 7 days, the intake of glucomannan was then gradually increased

  • for days 1-3, this dose was 1.5g per day
  • for days 4-7, the dose increased to 3g a day

This allowed the volunteers to adapt to the increased glucomannan supplement that was to follow.

For 21 days, the patients then consumed 1.5g of glucomannan with each meal. This maintained an intake of 4.5g of glucomannan a day for this period.

During days 15-21, individual stools were then analysed from both those in the control group and the glucomannan group.

Results

Consuming glucomannan significantly increased

  • the frequency of bowel movements per day
  • wet stool weight
  • dry stool weight

Glucomannan increased levels of

  • fecal lactobacilli
  • total bacteria

It also increased the daily fecal output of

  • bifidobacteria
  • lactobacilli
  • total bacteria 

Compared to the placebo, glucomannan also

  • decreased the relative proportion of clostridia

Glucomannan significantly lowered

  • fecal pH

Glucomannan increased

  • total SCFA (short-chain fatty acids)

Therefore, it also increased concentrations of the major products of SCFA:

  • acetate
  • propionate
  • i-butyrate
  • n-butyrate 

Glucomannan also made the passage of bowel movements easier for patients. 
In this study, glucomannan did not increase any side effects.

Conclusions

The results of this study show how dietary fibre such as glucomannan can promote healthy bowel habits.

One of the ways glucomannan can do this is by increasing stool mass. Glucomannan causes stools to hold a higher volume of water. Gas can also then be trapped in the stool. As observed in the study, consuming glucomannan each days also resulted in an increase in fecal weight. This additional bulk in the colon as well as the additional volume of gas can cause stools to pass faster through the bowel. This then results in more frequent bowel movements.

Colonic fermentation also occurs when dietary fibre such as glucomannan is consumed. A result of this fermentation is the growth of bifidobacteria and lactobacilli. Bifidobacteria and lactobacilli are major bacteria that are beneficial to the human gut. The presence of these bacteria in the gut have been shown to promote regular bowel movements.

During this process, SCFAs are also produced by bacteria in the gut, leading to a decrease in fecal pH. The fact that glucomannan increased levels of SCFAs and decreased fecal pH in this study shows that glucomannan also promotes colonic fermentation. Therefore, glucomannan can also treat constipation by promoting good bacteria through colonic fermentation. 

In this study, glucomannan was also shown to lower the amount of clostridia in their patients. Clostridia, which are a class of Firmicutes, are common in an unhealthy gut. 

Therefore, consuming dietary fibre such as glucomannan can help treat constipation. Glucomannan does this by promoting regular bowel movements as well as promoting good bacteria in the gut.

You can read more about good bacteria and the gut microbiome in our article on weight loss and microbiome health.

References

1. Chen H, Cheng H, Liu Y, et al. “Konjac acts as a natural laxative by increasing stool bulk and improving colonic ecology in healthy adults” in Nutrition Vol. 22 No. 11 (2006): 1112-1119.

2. Dreher M. “Fiber in Laxation and Constipation” in Dietary Fiber in Health and Disease (2018): 95-115.

3. Yang J, Wang H, Zhou L, et al. “Effect of dietary fiber on constipation: A meta analysis” in World Journal of Gastroenterology Vol. 18 No. 48 (2012): 7378-7383.