Backed by four major reviews, the BDA’s first-ever constipation guidelines separate science from myth, highlighting psyllium, kiwifruit, and magnesium oxide as proven allies for better gut health.
Study: British Dietetic Association Guidelines for the Dietary Management of Chronic Constipation in Adults. Image credit: Avocado_studio/Shutterstock.com
Chronic constipation is a troubling health condition that may have potentially major effects on long-term health. However, no clear dietary recommendations exist to treat it. To tackle this, the British Dietetic Association (BDA) recently published evidence-based and expert-endorsed guidelines to manage chronic constipation in adults. The report appeared in the Journal of Human Nutrition and Dietetics.
Introduction
Chronic constipation refers to bowel movements that are too few, too difficult, or both. It affects up to one in ten people worldwide and reduces their quality of life. Management and treatment efforts pose a significant financial burden.
Dietary strategies for constipation are widely used, primarily focused on increasing dietary fiber and fluid intake. However, they provide satisfactory relief for less than half the users. Current guidelines are vague, not supported by strong evidence, or are based on partial evidence. This prompted the BDA to publish the first-ever comprehensive evidence-backed guidelines to help advance patient care and improve patient outcomes.
About the study
These guidelines are designed for healthy adults with chronic constipation of unknown cause. While they may also benefit people whose constipation has a known underlying condition, the evidence used to develop them did not specifically include this group. They are intended for use by dietitians and other healthcare professionals in advising adults with chronic constipation.
The evidence for the current guidelines came from four systematic reviews and meta-analyses. The reviews covered people who were clinically diagnosed using widely recognized criteria or self-reported to have chronic constipation. A third group was diagnosed by relevant clinicians or study authors. Alternatively, they had one or more symptoms of constipation.
Broad definitions like these were necessary to ensure that the study population represented the general population looking for medical help for constipation at any level of healthcare.
Dietary approaches covered in the systematic reviews included fiber supplements, probiotics and synbiotics, vitamin and mineral supplements, whole diets, foods, and drinks. Only randomized control trials (RCTs) with placebo controls were included, except in studies of whole diets, foods, or drinks, where placebo designs are often impractical and less common. Non-RCT studies were excluded from the development of evidence-based recommendations.
Patient outcomes were classified by:
- How many participants benefited from the treatment
- Stool changes (frequency and consistency)
- Gut symptoms
- Adverse effects
- Quality of life
The systematic reviews covered 75 RCTs, which produced 59 recommendations. Most of these are related to fiber supplements and probiotics, among dietary supplement recommendations. For foods, recommendations covered kiwifruit, prunes, and rye bread, while drinks-related statements covered mineral-rich water.
The guideline statements were based on meta-analysis data using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) approach and a Delphi consensus survey among a multidisciplinary expert Guideline Steering Committee. Evidence was accepted only if supported by at least two randomized controlled trials (RCTs), and the strength of each recommendation was evaluated using GRADE-based criteria.
Study results
Surprisingly, there was no evidence to support whole diet approaches, meaning no recommendations could be made.
Of the 59 statements, eight were moderately supported by evidence. The rest had low or very low evidence-based support. Despite the low level of evidence, 27 statements were strong recommendations, backed by expert consensus or indirect evidence or with a high benefit-to-risk ratio, low cost, and high convenience.
“Strong” recommendations can still arise from low-certainty evidence when benefits clearly outweigh risks or when advice is widely applicable, feasible, and low-cost. Some strong recommendations also took the form of Good Practice Statements derived from expert consensus. There were 32 qualified statements applicable in specific conditions.
Overall, psyllium fiber supplements had a clinical benefit, softening and increasing stool frequency and reducing the severity of straining. These effects were significant at higher doses and overall durations. Fiber supplements containing polydextrose, inulin and other fibers, or galacto-oligosaccharides did not show an associated benefit.
The superiority of psyllium to prunes has not been established, indicating an open question for future study.
Increasing dietary fiber is often recommended for constipation. Still, only single RCTs or uncontrolled studies show the benefit of high-fiber foods like mango, figs, oat bran, flaxseed flour, or high-fiber cereal. More research is warranted to validate these findings. The overall benefit of a nonspecific high-fiber diet remains to be established, as does the role of increasing fluid intake at the same time.
However, the guidelines recommend using 10 g or more of fiber daily for clinical benefit, starting with low doses for at least four weeks to minimize adverse effects. Inulin-based supplements increase the chances of flatulence.
Magnesium oxide supplements improved stool frequency and quality of life, reducing constipation-related symptoms with few adverse effects. According to pooled trial data, participants were about three times more likely to respond to treatment than to a placebo. These supplements should be started at low doses, gradually increasing the dose as tolerated.
Rye bread (6-8 slices a day for three or more weeks) could be helpful as a substitute for white bread, increasing stool frequency. However, the guidelines note that rye bread may slightly worsen global constipation symptoms in some individuals, suggesting it should be used selectively. Kiwifruit (2 to 3 a day for four or more weeks) may be helpful, especially for people with bloating, abdominal pain and flatulence with psyllium. This is not true of kiwifruit supplements, which reduce abdominal pain but not constipation.
Mineral-rich water might relieve symptoms related to constipation treatment. It could be recommended according to the composition used in most studies in this area, which is several magnitudes higher than ordinary tap water in the UK.
The role of probiotic supplements indicates some clinical benefit, but further research is required to understand the specific strains and effects that are useful in constipation. According to these recommendations, they may be used at the patient’s wish for at least four weeks to test for any benefit.
There is inadequate rigorous research to support the use of fermented food, but the suggested effectiveness indicates the need for well-designed RCTs to explore this approach. Food products with inactivated bacteria are also recommended to be useful, but more study is required.
Senna has long been recommended for constipation, but with no evidence from two RCTs. The same is the case with high-dose vitamin C. Rice, bananas and certain other foods are claimed to promote constipation, but without adequate research-backed evidence.
Conclusions
These are the first comprehensive evidence-based dietary guidelines for the management of constipation based upon a robust systematic review and GRADE processes.
Some studies provide first-time recommendations for supplements, foods or drinks, allowing their rapid integration in clinical practice for better patient outcomes.
In addition, by addressing specific constipation-related symptoms, they can guide personalized dietary advice. These statements also summarize positive, adverse, and null effects, further promoting evidence-based discussions. It is stressed that most recommendations are provisional and highlight major research gaps, especially regarding whole-diet and fermented food interventions.
Further research is also needed to determine long-term outcomes and optimal dosing for some dietary components, including prebiotics and kiwifruit.
Download your PDF copy now!
Why young athletes should think twice before using supplements