Adults with chronic functional constipation experienced more frequent bowel movements and better stool consistency after taking a mixture of dietary fiber from multiple food sources in a placebo-controlled trial.
Study: Combining dietary fiber from different food sources as a treatment for adults with functional constipation: A randomized clinical trial. Image credit: triocean/Shutterstock.com
A recent study in the journal Food Science and Nutrition reports that a combination of dietary fibers from various foods significantly improved symptoms of functional constipation in a small randomized clinical trial compared with placebo.
Chronic constipation remains difficult to treat
Constipation can present as fewer than three bowel movements per week or as irregular bowel movements, hard or loose stools, excessive straining during bowel movements, or a feeling of incomplete emptying. Chronic constipation, lasting three or more months, is reported in up to 15% of the population. It reduces quality of life, accounts for a significant share of health care costs, and is often difficult to treat.
A common cause of chronic constipation is functional constipation. Adequate hydration and the inclusion of whole grains, legumes, vegetables, and fruits in the diet are the primary treatment strategies for constipation. These are valuable sources of dietary fiber that pass through the large intestine. There, fiber is either fermented by gut microbes to produce beneficial bioactive compounds or absorbs water to increase stool bulk. Insoluble fiber, if present, mechanically induces mucus secretion from the intestinal mucosa, increasing motility.
However, most people consume very few vegetables. Previous studies suggest that, in the short term, increasing vegetable intake is associated with increased abdominal gas, distension and bloating, thereby promoting laxative use.
However, laxatives do not provide uniform relief. The overall lack of effective and well-tolerated treatments motivated the current study, a small, single-center, randomized clinical trial that compared a multisource dietary fiber supplement with placebo. The researchers used a combination of resistant dextrin from wheat starch, pectins, insoluble fiber from citrus oat species and fiber, which also yield β-glucan and starch.
This was provided in 6.5g servings, which contained 5g of dietary fibre. Of this, approximately 80% was soluble and 20% insoluble fiber.
Randomized trial tested fiber supplement versus placebo
Researchers conducted a single-center, randomized, double-blind, placebo-controlled clinical trial with 54 Caucasian adults who had chronic functional constipation. They were randomly assigned to receive either the fiber supplement or a placebo twice a day for 28 days. In addition, they continued to follow their normal diet. Instructions were given on proper defecation, proper fluid intake and the need to record any other treatments. These steps were aimed at ensuring compliance with actual conditions of use.
They kept a bowel function diary which recorded the number of spontaneous complete bowel movements, time and consistency of stools using the Bristol Stool Form Scale (BSFS). Difficulty in defecation, symptoms of constipation such as heaviness, bloating, flatulence and pain, and the need for laxatives or other measures to induce bowel movements were also investigated.
The fiber supplement increased bowel movements within two weeks
The treatment group showed a progressive increase in the number of spontaneous complete voids from baseline to 1 week after the last dose and between successive weekly measurements. In contrast, the control group showed a moderate increase between the initial and last week of treatment, but not at the one-week follow-up.
A significant increase in the number of spontaneous complete voids per week was visible between the groups from the end of the second week, from one more at the end of week 2 to another two by the end of the follow-up period.
Similarly, stool consistency improved as reflected by progressively higher BSFS scores during treatment, although it fell slightly during the follow-up week. The difference was observed from baseline to the end of week 4 and week 5, starting at 0.55 at the end of week 2 and ending at 1.5 at the end of the follow-up week. The largest difference, 1.7, occurred at the end of week 4.
The effect of the treatment varied according to the individual symptoms of constipation. For example, abdominal distension decreased progressively over the treatment period in the treatment group but not in the control group, as did weight and abdominal distension. Interestingly, stretch was higher in the treatment group at baseline. Flatulence was also significantly improved in the treatment group, while abdominal pain was not significantly different between groups.
The supplement was well tolerated, with no adverse events reported and no participants requiring rescue laxative therapy during the study.
Different fibers may work through complementary mechanisms
The results are supported by a meta-analysis of previous randomized controlled trials showing, in particular, the benefits of pectins on bowel function, with high doses of fiber linked to the greatest improvements in stool frequency and consistency when used for more than four weeks of treatment.
Oat fiber has also been associated with improvement in multiple areas related to constipation. Resistant dextrin has been shown to act as a prebiotic, increasing the production of short-chain fatty acids by gut bacteria, while also regulating enzyme activity and stabilizing gut microflora.
Thus, this combination may have complementary effects on the gut, improving function and relieving constipation.
The small trial limits the wider applicability of the findings
The study has several limitations. Its sample size was small, limiting its generalizability. The single-center design and inclusion of only Caucasian participants further limits the scope to which the findings can be applied. The duration is too short to measure long-term effects. Residual confounding by changes in diet or behavior cannot be excluded.
Furthermore, many results were based on participant-reported symptom questionnaires, which are inherently subjective and may be affected by reporting bias. The one-week follow-up was also too short to determine whether the benefits would persist after treatment was discontinued.
Combined dietary fiber promises chronic constipation
The combination of resistant dextrin, pectins and insoluble citrus fiber and oat fiber can provide rapid and clinically significant relief of constipation and its symptoms in a population with chronic functional constipation at a daily dose of 13 g.
This dose is lower than the doses of the individual fiber components commonly used separately, while avoiding the discomfort associated with the same dose of resistant dextrin.
Future larger multicenter studies should validate these results, examine how long the improvement persists, and investigate changes in gut microbiota.
