“”Lack of fiber in the diet was first postulated in 1971 as the cause of diseases such as diverticulosis, hemorrhoids and colorectal cancer. Since then, partly due to widespread media publicity, it is now widely accepted that dietary fiber is a necessary component of a healthy diet and is required for normal bowel movement. It is popularly used in the management of constipation by the publicLack of fiber in the diet was first postulated in 1971 as the cause of diseases such as diverticulosis, hemorrhoids and colorectal cancer. “
“Since then, partly due to widespread media publicity, it is now widely accepted that dietary fiber is a necessary component of a healthy diet and is required for normal bowel movement[2–5]. It is popularly used in the management of constipation by the public and by many doctors. Insoluble fiber is known to increase stool weight and decrease colonic transit time[6,7]. Fiber is said to aid in water retention in the colon and results in stools that are less dry and easier to evacuate. However, the reality is that stool moisture content remains at 70%-75% regardless of the amount of fiber and water consumed[7,8].”
“There were 16 males (25.6%) and 47 (74.4%) females, median age 47 years (range, 20-80 years) included in the study. At the commencement of the study, all patients were already on a high fiber diet or taking fiber supplements. After 2 wk of a no fiber diet, patients were asked to continue on as little fiber in the diet as they were able to follow if this were to give them relief from their symptoms.
At 6 mo, 41 patients continued on a no fiber diet and 16 were on a reduced fiber diet. The remaining 6 patients continued on a high fiber diet for various reasons including being vegetarians or inability to stop consuming dietary fiber for religious or personal reasons.
The median age of patients who stayed on a no fiber diet was 46 years (range, 21-80 years), on a reduced fiber diet was 45 years (range, 20-65 years) and on a high fiber diet was 59 years (range, 28-75 years). There was no statistical significant difference in age between the 3 groups. There was also no statistical difference in sex between the 3 groups (Table (Table11).
At 6 mo follow-up, the interval between bowel movements decreased with the reduction in fiber intake (P < 0.001). Forty one patients who completely stopped fiber intake had their bowel frequency increased from one motion in 3.75 d (± 1.59 d) to one motion in 1.0 d (± 0.00 d) (P < 0.001). Of 16 patients who reduced their dietary fiber intake, 12 patients had daily bowel movement, 3 had one bowel movement every 2 to 3 d and one had a bowel movement every 4 to 6 d, giving one motion per 1.9 d (± 1.21 d) on a reduced fiber diet compared with 1 motion per 4.19 d (± 2.09 d) on a high fiber diet (P < 0.001). There was no change in the frequency of bowel movement for patients who continued with high dietary fiber intake, with one motion per 6.83 d (± 1.03 d) before and after consultation (P = 1.00).
There was also a difference between the groups in the proportion of patients with associated symptoms. For symptoms of bloating, all of those on a high fiber diet continued to be symptomatic, while only 31.3% in the reduced fiber group and none of the no fiber group had symptoms (0%, P < 0.001) (Table (Table22).
With regards to straining, all those on a no fiber no longer had to strain to pass stools. Of those who reduced dietary fiber, 7 of 16 showed improvement while the symptoms remain unchanged in those who remained on a high fiber diet (P < 0.001 between groups).
Symptoms of abdominal pain only improved in patients who stopped fiber completely while those who continued on a high fiber diet or reduced fiber diet did not show any improvement (Table (Table2).2). In addition, those on a no dietary fiber diet no longer had symptoms of anal bleeding.
It is well known that increasing dietary fiber increases fecal bulk and volume. Therefore in patients where there is already difficulty in expelling large fecal boluses through the anal sphincter, it is illogical to actually expect that bigger or more feces will ameliorate this problem. More and bulkier fecal matter can only aggravate the difficulty by making the stools even bigger and bulkier. Several reviews and a meta-analysis had already shown that dietary fiber does not improve constipation in patients with irritable bowel diseases[18–21].
The role of dietary fiber in constipation is analogous to cars in traffic congestion. The only way to alleviate slow traffic would be to decrease the number of cars and to evacuate the remaining cars quickly. Should we add more cars, the congestion would only be worsened. Similarly, in patients with idiopathic constipation and a colon packed with feces, reduction in dietary fiber would reduce fecal bulk and volume and make evacuation of the smaller and thinner feces easier. Adding dietary fiber would only add to the bulk and volume and thus make evacuation even more difficult.
In conclusion, contrary to popularly held beliefs, reducing or stopping dietary fiber intake improves constipation and its associated symptoms.”