Stopping or reducing dietary fiber intake reduces constipation and its associated symptoms (Sep 2012, n=63) Diet

[NiroZ]

https://pmc.ncbi.nlm.nih.gov/articles/PMC3435786/

Abstract
AIM: To investigate the effect of reducing dietary fiber on patients with idiopathic constipation.

METHODS: Sixty-three cases of idiopathic constipation presenting between May 2008 and May 2010 were enrolled into the study after colonoscopy excluded an organic cause of the constipation. Patients with previous colon surgery or a medical cause of their constipation were excluded. All patients were given an explanation on the role of fiber in the gastrointestinal tract. They were then asked to go on a no fiber diet for 2 wk. Thereafter, they were asked to reduce the amount of dietary fiber intake to a level that they found acceptable. Dietary fiber intake, symptoms of constipation, difficulty in evacuation of stools, anal bleeding, abdominal bloating or abdominal pain were recorded at 1 and 6 mo.

RESULTS: The median age of the patients (16 male, 47 female) was 47 years (range, 20-80 years). At 6 mo, 41 patients remained on a no fiber diet, 16 on a reduced fiber diet, and 6 resumed their high fiber diet for religious or personal reasons. Patients who stopped or reduced dietary fiber had significant improvement in their symptoms while those who continued on a high fiber diet had no change. Of those who stopped fiber completely, the bowel frequency increased from one motion in 3.75 d (± 1.59 d) to one motion in 1.0 d (± 0.0 d) (P < 0.001); those with reduced fiber intake had increased bowel frequency from a mean of one motion per 4.19 d (± 2.09 d) to one motion per 1.9 d (± 1.21 d) on a reduced fiber diet (P < 0.001); those who remained on a high fiber diet continued to have a mean of one motion per 6.83 d (± 1.03 d) before and after consultation. For no fiber, reduced fiber and high fiber groups, respectively, symptoms of bloating were present in 0%, 31.3% and 100% (P < 0.001) and straining to pass stools occurred in 0%, 43.8% and 100% (P < 0.001).

CONCLUSION: Idiopathic constipation and its associated symptoms can be effectively reduced by stopping or even lowering the intake of dietary fiber.

Click to shrink...

While this study serves to make the point that constipation is not always just about fibre, it's not a very well designed study.
For one, the recruitment process is unclear. They were patients at a clinic and had medical causes ruled out, but it's not stated if this is all patients who had medical causes ruled out who attended the clinic, or just some of them. This matters because it's possible some clinic attendees were supported to increase their fibre or found their own resolution and stopped attending the clinic and then excluded from the trial, skewing the results.

Second, they used the participants as their own controls. The benefit of a control group is that you can gauge if they would have recovered if you did nothing. There is a method to use participants as their own control, but that is to do it ABAB, where A is the intervention and B is where the intervention is removed. They did not do this, but rather had them go no fibre for 2 weeks and then saw if they remained on the diet and it's effect.

Third, they didn't consider FODMAPs. The idea of FODMAPs had been kicking around since 2005, so they should have been aware of the idea in 2012. This means that it is highly likely that it wasn't the removal of fibre, but eliminating fibrous foods that were one of the FODMAPs that they were sensitive to.

Forth, they were unclear just how much fibre each person was consuming. They do state that "At the commencement of the study, all patients were already on a high fiber diet or taking fiber supplements." But nowhere is it defined what constitutes high fibre or level of supplementation. Nor is it explained what level is reduced fibre. And given that no fibre is impossible unless you stop eating plants altogether, what level they considered no fibre.