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Chronic Constipation In Adults : A Systematic Study On Dietary Effects

Chronic Constipation In Adults : A Systematic Study On Dietary Effects


The management of chronic constipation often involves dietary interventions, yet until now, there has been a lack of a comprehensive systematic review and meta-analysis regarding the impact of various foods, drinks, and diets on treatment response, stool output, gut transit time, symptoms, quality of life, adverse events, and compliance in adults with chronic constipation.


The objective of this study was to fill this gap by conducting a thorough investigation. The researchers identified relevant studies using electronic databases up to July 12, 2023.

The inclusion criteria covered intervention trials, encompassing randomized controlled trials (RCTs), non-randomized, and uncontrolled studies.

The risk of bias was evaluated using Cochrane 2.0 for RCTs and JBI Critical Appraisal for uncontrolled trials. The analysis focused on RCTs and employed risk ratios (RRs), mean differences (MDs), and standardized mean differences with 95% confidence intervals, utilizing random-effects models.

The study included 23 trials involving 1714 participants, comprising 17 RCTs and 6 uncontrolled trials. Various interventions were explored, such as kiwi fruit, high-mineral water, prunes, rye bread, mango, fig, cereal, oat bran, yogurt, water supplementation, prune juice, high-fiber diet, and a no-fiber diet.


Notable findings indicated that fruits, particularly kiwi fruit, demonstrated a higher stool frequency compared to psyllium, whereas prunes showed no significant difference.

Rye bread was associated with increased stool frequency compared to white bread. High-mineral water exhibited a higher treatment response compared to low-mineral water.


The study suggests that certain foods, such as fruits and rye bread, may contribute to improvements in outcomes related to constipation.

However, the existing evidence on foods, drinks, and diets in the context of constipation is limited, underscoring the need for further well-designed randomized controlled trials to enhance our understanding of these interventions.



Chronic constipation, a prevalent functional bowel disorder, significantly impairs the quality of life for affected individuals and imposes substantial economic burdens on both individuals and healthcare systems.

Recognizing the pivotal role of diet in managing this condition, current guidelines primarily advocate for increased dietary fiber.

However, they provide limited guidance on specific foods, beverages, or comprehensive dietary regimens that might enhance treatment outcomes.

The recommended dietary measures include not only fiber supplementation but also emphasize adequate fluid intake and the consumption of vegetables, whole grains, and certain fruits with high sorbitol content, such as apples.

The rationale behind these recommendations lies in the potential of dietary fiber to increase stool bulk, soften stools through its high water-holding capacity, and influence gut muscular contractions and transit time.

Sorbitol, a nonabsorbable sugar alcohol found in certain fruits, is believed to exert an osmotic effect, increasing luminal water content and contributing to stool softening.


Despite these considerations, there exists a noticeable dearth of empirical evidence supporting the targeted use of specific foods and beverages in chronic constipation.

This gap in knowledge hampers both informed self-management practices and clinical care, potentially contributing to the high levels of dissatisfaction reported by individuals with constipation regarding the effectiveness of available treatment options.


While systematic reviews have explored the efficacy of certain dietary interventions in chronic constipation, it’s important to note that these reviews have primarily focused on supplement forms rather than the natural counterparts of these interventions.

For instance, while improvements in constipation symptoms have been demonstrated with fiber supplements, the evidence regarding the impact of fiber-containing foods remains largely unexplored.

Similarly, systematic reviews have delved into the effects of probiotics and food supplements, yet investigations into the comprehensive impact of whole foods, beverages, and dietary patterns in the context of chronic constipation are notably absent.


This systematic review and meta-analysis aim to bridge this gap in knowledge by comprehensively investigating the effects of various foods, drinks, and diets on different aspects of chronic constipation in adults.

The outcomes of interest include treatment response, stool output, gut transit time, symptoms, quality of life, adverse events, and compliance.

By shedding light on the nuanced interactions between dietary factors and chronic constipation, this study seeks to provide valuable insights that can inform both self-management strategies and clinical care for individuals grappling with this challenging condition.



This systematic review and meta-analysis meticulously adhered to the methodological standards outlined in the Cochrane Handbook for Systematic Reviews of Interventions and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses updated guidelines. A pre-established protocol was registered in advance with PROSPERO (CRD42021241072).


Eligibility Criteria


The eligibility criteria were methodically crafted using the PICOS framework (Patient, Intervention, Comparators, Outcome, Study design).

The inclusion criteria encompassed intervention trials that investigated the effects of foods (including herbs and spices), drinks, and diets in adults with chronic constipation, specifically focusing on measurable constipation outcomes.

Given the limited availability of randomized controlled trials (RCTs) and the inherent challenges associated with designing and blinding controls in interventions involving food and diet, uncontrolled trials were also considered eligible.


Search Strategy


A comprehensive search strategy was employed, entailing a systematic exploration of electronic databases, hand-searching of conference abstracts, and meticulous back-searching of reference lists from eligible studies and relevant review articles.

Three prominent electronic databases—MEDLINE, EMBASE, and The Cochrane Central Register of Controlled Trials—were systematically queried. 

No restrictions were imposed on language or publication date. Additionally, the US National Institute of Health clinical trials register was scrutinized to identify unpublished trials.

The search extended until July 12, 2023, to ensure inclusivity of the latest available evidence. Conference abstracts from notable gatherings such as Digestive Disease Week, British Dietetic Association, British Society of Gastroenterology, and the European Society for Clinical Nutrition and Metabolism were also scrutinized.


Selection Process


The process of study selection involved importing references into a reference manager (EndNote X9) for initial eligibility assessment. Two independent reviewers meticulously screened titles and abstracts, followed by a detailed examination of full-text articles against the predefined eligibility criteria.

Any foreign-language articles were translated to ensure a comprehensive understanding. Discrepancies in study selection were resolved through consultation with a third and fourth reviewer.


Data Collection Process


Two reviewers independently extracted data from eligible studies onto a standardized form, as outlined. Cross-verification of extracted data was conducted, and any disparities were resolved through discussion.

In cases where articles provided insufficient data, efforts were made to contact the authors to obtain the required information.

Intention-to-treat analyses were prioritized in data extraction, and for dichotomous data, drop-outs were assumed to be treatment failures.


Risk of Bias Assessment


Risk of bias assessment was undertaken independently by two reviewers, utilizing the Cochrane risk-of-bias 2.0 tool for RCTs and the JBI Critical Appraisal checklist for single-arm trials.

Discrepancies were resolved through discussion with a third reviewer. Trial registrations and protocols were meticulously reviewed to ensure alignment with pre-specified outcomes.


Data Synthesis


Both quantitative (meta-analysis) and narrative synthesis were conducted, with the approach guided by the study design. Given the observed heterogeneity in interventions, comparators, and study designs, a hierarchy was established to facilitate meaningful quantitative synthesis.

RCTs with an intervention duration of ≥2 weeks and cross-over designs with a washout period of ≥2 weeks were prioritized for meta-analysis. For studies not included in the meta-analysis, a narrative synthesis was provided.

Subgroup analyses were performed to explore the effects of intervention types, with statistical significance set at p < 0.1 for subgroup analyses.


This systematic review and meta-analysis rigorously applied a well-defined set of inclusion and exclusion criteria, ensuring a methodologically robust synthesis of evidence to investigate the effects of foods, drinks, and diets on chronic constipation outcomes in adults.



In the course of this investigation, a comprehensive analysis was conducted on 10,905 non-duplicated records, ultimately identifying 23 studies that fulfilled the predefined inclusion criteria.

These studies, involving 1714 participants with chronic constipation, were meticulously examined for their contribution to the understanding of the effects of various foods and drinks on constipation outcomes in adults.


The studies encompassed 17 randomized controlled trials (RCTs) and six uncontrolled trials, with a diverse range of interventions such as kiwifruit, prunes, mango, fig paste, rye bread, cereal, oat bran biscuits, pasteurized yogurt, high-mineral water, water supplementation, prune juice, and different diets, including high-fiber and no-fiber regimens.

The inclusion criteria were crafted with precision, considering patient demographics, intervention specifics, comparators, outcomes, and study design.


The meta-analysis findings were systematically presented for specific food and drink categories.

For instance, the analysis of fruits, including kiwifruit, prunes, and mango, compared with psyllium, revealed that fruits were associated with a favorable response to treatment, increased stool frequency, softer stool consistency, and improved gastrointestinal symptoms.


In the case of rye bread interventions, meta-analysis demonstrated that rye bread resulted in higher stool frequency, softer stool consistency, and shorter gut transit time compared to white bread, but it was associated with higher integrative symptom scores and difficulty in defecation.


The investigation extended to beverages, with high-mineral water interventions exhibiting positive effects on the response to treatment, stool frequency, and stool consistency compared to low-mineral water. However, some studies showed high-risk bias, raising concerns about the robustness of the evidence.


Additionally, water supplementation alongside a high-fiber diet and prune juice interventions demonstrated positive effects on stool frequency and consistency, while a high-fiber diet, in general, did not significantly impact stool frequency and was associated with increased flatulence.


Remarkably, reducing dietary fiber intake in a no-fiber diet intervention led to an increase in stool frequency over a six-month period, highlighting the intricate relationship between dietary components and constipation outcomes.


Throughout the analysis, the risk of bias in the selected studies was meticulously evaluated, considering factors such as blinding, randomization, and missing data. Compliance rates were also reported, shedding light on the adherence of participants to the prescribed interventions.


This rigorous investigation has provided valuable insights into the effects of diverse foods and drinks on chronic constipation outcomes in adults, contributing substantively to the existing body of knowledge in the field.



This systematic review and meta-analysis focused on examining various foods, drinks, and diet interventions for chronic constipation, primarily assessed through randomized controlled trials (RCTs).

The investigation revealed a limited number of interventions studied, with kiwifruits, prunes, rye bread, and high-mineral water being the subjects of more than one RCT. Notably, mango, fig products, pasteurised yoghurt, prune juice, high-fibre cereal, and oat bran biscuits were each investigated in only one RCT or uncontrolled study.


The review highlighted the effectiveness of fruits, particularly kiwifruits, in improving stool frequency and consistency when compared to psyllium, a well-established fiber supplement for constipation.

Kiwifruits, owing to their soluble and insoluble fiber content, along with the presence of actinidin, a proteolytic enzyme, demonstrated positive effects on gastrointestinal symptoms. Prunes, however, did not show a superior impact on stool output compared to psyllium, emphasizing the need for further adequately powered studies to establish their efficacy.


Rye bread, despite increasing stool frequency slightly, was associated with adverse effects such as flatulence. The studies on rye bread were deemed high risk, and caution is advised when interpreting their findings.

Only one RCT examined a high-fibre diet (25–30 g/day), and it was discontinued due to lack of efficacy, demonstrating worsened flatulence and abdominal distention compared to a low-fibre diet.

Another study assessing a ‘no-fibre’ diet showed positive effects on constipation outcomes but lacked a controlled design and was also at high risk of bias.


High-mineral water, rich in magnesium sulfate, demonstrated increased response to treatment compared to low-mineral water but did not significantly impact other constipation outcomes.

The review suggests the need for more high-quality RCTs to explore dietary interventions comprehensively in chronic constipation, particularly focusing on whole diet approaches and differentiating between food sources and fiber supplements.


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