Introduction

Functional gastrointestinal disorders (FGIDs), including irritable bowel syndrome (IBS), affect a substantial proportion of the population and are associated with significant impairment in quality of life. These disorders are characterized by symptoms such as abdominal pain, bloating, flatulence, diarrhea, or constipation in the absence of demonstrable structural abnormalities. Globally, it is estimated that up to 40% of the population presents some form of FGID, whereas the prevalence of IBS, according to the Rome IV criteria, is 3.8%^1,2.

According to the global study conducted by the Rome Foundation across 33 countries and including more than 73,000 participants, 40.3% of individuals surveyed online and 20.7% of those surveyed through household interviews met criteria for at least one FGID, based on the Rome IV criteria. Regarding irritable bowel syndrome, prevalence was 4.1% in internet-based surveys and 1.5% in household surveys, with higher frequency observed in women³.

In Latin America, the prevalence of irritable bowel syndrome reaches 6.98%⁴. In Colombia, studies conducted in adult populations have reported figures as high as 24.0%⁵, suggesting a substantial national disease burden and potential regional variation associated with dietary, cultural, and diagnostic factors. The low-FODMAP diet (LFD) represents a non-pharmacological therapeutic strategy with demonstrated efficacy in reducing gastrointestinal symptoms. Its implementation consists of three phases: elimination, gradual reintroduction, and individualized adaptation, with the aim of achieving sustained symptom control⁶. FODMAPs are poorly absorbed carbohydrates that increase intestinal osmolarity and undergo colonic fermentation, leading to the production of gas and short-chain fatty acids. These pathophysiological mechanisms contribute to symptoms such as bloating, abdominal pain, and altered gastrointestinal motility. These effects support the use of the LFD as a therapeutic strategy for functional gastrointestinal disorders^7,8.

Although the efficacy of the LFD is supported by scientific evidence, its clinical implementation continues to face challenges related to professional knowledge, food availability, and sociocultural factors. This underscores the need to address existing gaps and to develop evidence-based recommendations to optimize its application in the management of functional gastrointestinal disorders⁹.

In this context, the objective of the present systematic review is to synthesize the available scientific evidence on the efficacy and clinical applicability of the LFD in adult patients, with emphasis on symptom reduction, improvement in quality of life, and adherence to nutritional treatment.

Materials and methods

This systematic review was conducted in accordance with the PRISMA 2020 methodology (Preferred Reporting Items for Systematic Reviews and Meta-Analyses)¹⁰. The protocol was registered in the International Prospective Register of Systematic Reviews (PROSPERO) under ID 1005339. The review received approval from the Research Ethics Committee of the School of Medicine at Universidad Nacional de Colombia (B.FM.1.002-CE-042-25).

The search strategy was carried out on March 6, 2025, across the bibliographic databases PubMed, ScienceDirect, Scopus, SciELO, Embase (Elsevier), Latin American and Caribbean Health Sciences Literature (LILACS), and The Cochrane Library (CLIB), which includes the Cochrane Central Register of Controlled Trials (CENTRAL).

From an epidemiological perspective, studies meeting predefined eligibility criteria based on the PICO framework were included. The target population consisted of adults (≥18 years) diagnosed with functional gastrointestinal disorders, primarily irritable bowel syndrome or functional dyspepsia, according to the Rome III or Rome IV criteria. The intervention evaluated was the LFD, applied in any of its phases, and compared with conventional diets, unstructured diets, or usual care without a specific dietary intervention. Outcomes included symptom reduction, improvement in quality of life, and treatment adherence. Both observational and experimental study designs were considered, including randomized controlled trials, cohort studies, case-control studies, and systematic reviews with meta-analysis. The search was limited to publications between 2015 and 2025 in English, Spanish, Portuguese, or French.

From a methodological perspective, studies involving populations not representative of the target clinical population were excluded. These included individuals younger than 18 years, frail older adults (≥70 years), and patients with organic gastrointestinal diseases such as inflammatory bowel disease, celiac disease, or cancer. Animal studies, in vitro research, and non-primary publications (narrative reviews, editorials, letters, case reports, and abstracts without complete data) were also excluded.

Studies that did not clearly describe the LFD implementation protocol, had follow-up periods shorter than four weeks, or failed to assess relevant clinical outcomes were excluded. Studies without defined comparator groups or those evaluating experimental diets different from conventional dietary approaches were also excluded. Only studies reporting clinically relevant outcomes, such as reduction in digestive symptoms, improvement in quality of life, or dietary adherence, were considered eligible.

The study screening process followed the methodological classification established by PROSPERO as “studies screened by one person (or machine) and verified by at least one other person (or machine),” ensuring independent double review to minimize selection bias. Reference management, duplicate detection, and streamlining of title, abstract, and full-text screening were conducted using the online platform Rayyan¹¹, a tool specifically designed for systematic reviews. Disagreements between reviewers were resolved by consensus or through consultation with a third evaluator.

Additionally, a complementary search approach known as the snowball method was applied. This strategy involved reviewing the reference lists of included studies as well as articles citing them in order to identify potentially relevant additional research. This approach increased the sensitivity of the search process and optimized the identification of pertinent studies, particularly those related to clinical efficacy and contextual implementation of the LFD in Latin American countries, where the literature may be dispersed or less extensively indexed in major databases.

Data extraction was conducted independently by two researchers, and discrepancies were resolved through consensus. Key methodological and clinical characteristics of clinical trials and systematic reviews with meta-analysis were collected, including information on study design, population, intervention, and outcomes. Authors were contacted when necessary to clarify or complete missing information.

Risk of bias was independently assessed by two reviewers using the Cochrane Risk of Bias 2.0 (RoB 2.0) tool in its Excel version (version 7). This instrument evaluates the methodological quality of randomized controlled trials across five key domains and provides an overall judgment regarding risk of bias. Discrepancies between reviewers were resolved through discussion and, when necessary, with the involvement of a third evaluator¹².

Results

A total of 1,750 records were identified through searches across multiple databases. Of these, 947 were removed as duplicates, and 592 were excluded after initial screening because they did not align with the objective of the review. During title and abstract screening, an additional 174 articles were excluded. Fifteen more were excluded after full-text assessment because they did not meet the established methodological criteria (Figure 1). Ultimately, 22 studies were included in the systematic review: 15 randomized controlled trials (Tables 1 and 2) and 7 systematic reviews with meta-analysis (Table 3).

Figure 1 PRISMA flow diagram for study selection. Image property of the authors. 

The findings of this review are organized into primary and additional outcomes. Primary outcomes include reduction of gastrointestinal symptoms, comparison with other dietary interventions, effectiveness according to IBS subtype, and the role of dietary education. The reintroduction phase, impact on quality of life, treatment adherence, changes in intestinal microbiota, and nutritional safety were also evaluated. Additional outcomes included effects on body weight and BMI, mental health, functional well-being, sleep quality, and changes in dietary composition (Figure 2).

Figure 2 Clinical effects associated with the low-FODMAP diet in patients with IBS. Image property of the authors. 

The available evidence supports the role of the LFD in reducing gastrointestinal symptoms, modulating the intestinal microbiota, improving mental health, enhancing sleep quality, supporting body weight control, and improving quality of life. These findings reflect the multidimensional benefits of the diet across physical, psychological, and metabolic domains in the management of IBS.

Discussion

This systematic review synthesizes recent evidence on the efficacy and clinical applicability of the low-FODMAP diet (LFD) in adults with irritable bowel syndrome. The findings consistently indicate a significant reduction in gastrointestinal symptoms, particularly among patients with diarrhea-predominant or mixed subtypes, as well as meaningful improvements in quality of life and psychological dimensions. Overall, the evidence supports the LFD as an effective dietary intervention for symptomatic management of irritable bowel syndrome and improvement of overall patient well-being³⁴, with high acceptability and a low risk of adverse effects when implemented with professional guidance³⁵. Furthermore, clinical practice guidelines for IBS issued by the National Institute for Health and Care Excellence (NICE) and the World Gastroenterology Organisation (WGO) recognize the LFD as an effective therapeutic option^36,37.

Regarding gastrointestinal symptoms, findings were consistent across studies, demonstrating significant symptom reduction following adherence to the LFD compared with conventional diets or placebo interventions^34,35,38-44. This pattern has been observed in both European and Latin American contexts, where improvements in abdominal pain, bloating, stool frequency, and quality of life have also been reported^45,46. These outcomes were primarily evaluated using validated instruments such as the IBS-SSS, strengthening the reliability of the evidence, although the inherent limitations of self-reported scales are acknowledged.

The LFD was consistently associated with improvements in quality of life among patients with IBS, with benefits observed in psychosocial domains compared with sham dietary interventions³⁵ and sustained improvements over both short- and long-term follow-up in pain, vitality, and social functioning⁴⁰. Quality of life increased significantly across all IBS-QOL domains, with an overall improvement of approximately 14 points⁴⁶. No relevant differences were identified according to the level of dietary adherence or degree of professional support⁴⁷. Improvements were more pronounced in patients with IBS-D and IBS-M, particularly in dysphoria, body image, and activity interference, whereas in IBS-C improvement was limited primarily to dysphoria⁴⁸. Additionally, seven of the nine quality-of-life domains evaluated improved following dietary intervention⁴⁴.

Dietary adherence plays a crucial role in intervention success, long-term willingness to maintain the diet, and improvement across multiple health dimensions. Professional support has been consistently identified as a determining factor in adherence across several studies^49-51. Evidence also indicates that the LFD may demonstrate enhanced effectiveness when combined with complementary therapies such as cognitive behavioral therapy, yoga, meditation, or hypnotherapy^38,52. Similarly, the incorporation of functional food components, such as turmeric extracts, has demonstrated reductions in abdominal bloating and intestinal dysbiosis⁵³. The most frequently reported reasons for discontinuation include limited time availability to follow the diet, occupational constraints related to cost, and motivational factors⁴⁷.

Recent findings have questioned the necessity of strict restriction of all FODMAP components in IBS management. Eswaran et al.⁵⁴ demonstrated that after completion of the LFD phase, only fructans induced statistically significant worsening of abdominal pain during reintroduction, whereas galactooligosaccharides increased bloating without a clear effect on pain. Similarly, Singh et al.⁵⁵ compared a traditional low-FODMAP diet with a simplified version restricting only fructans and galactooligosaccharides. Both groups demonstrated similar clinical response rates; however, the traditional LFD showed higher discontinuation rates due to adherence difficulties and tolerability concerns. These findings underscore the importance of individualized dietary strategies and highlight that not all FODMAP components exert equivalent effects across patients. They also reinforce the need to incorporate key variables such as adherence and dietary sustainability into clinical evaluation, factors frequently underreported in systematic reviews but highly relevant in clinical practice.

Adverse effects were minimal and generally transient, with some studies reporting mild symptom worsening in a small proportion of participants³⁵. The LFD appears safe in the short term; however, further evidence is required to establish long-term safety.

A relevant aspect identified was the impact on the intestinal microbiota. Most studies report a significant reduction in Bifidobacterium, which may compromise microbial diversity and contribute to dysbiosis due to restriction of prebiotic substrates, with potential long-term implications^35,56-58. A general reduction in total microbiota abundance and butyrate production has also been described, although multistrain probiotic supplementation may mitigate these effects⁵⁶. Regarding bacterial composition, the LFD has been associated with reduced Lactobacillus. In patients with pain-predominant IBS (IBS-P), increased abundance of Bacteroides and reduced pathogenic bacteria have been reported, effects not observed in unsubtyped IBS (IBS-S) or in healthy controls^59,60.

Regarding nutritional status, studies indicate that both the standard LFD and adapted versions do not produce significant changes in anthropometric parameters or hydration status in the short or long term^40,48. Nevertheless, weight loss or gain has been observed in some patients, suggesting heterogeneous individual responses and highlighting the need for nutritional monitoring³⁹. A significant reduction in body fat percentage has also been reported following intervention⁶¹.

Beneficial psychological effects associated with the LFD have also been demonstrated. The findings of this review are supported by clinical trials that evaluated psychological outcomes, showing significant improvements in symptoms of anxiety and depression, sleep quality, and fatigue⁴⁰.

The LFD also modifies habitual dietary patterns through the exclusion of commonly consumed foods such as wheat, dairy products, and certain fruits and vegetables. Although intake of energy, protein, and fat generally remains stable, carbohydrate and fiber intake tends to decrease, which may represent a disadvantage for patients with IBS-C⁶². Despite concerns regarding potential nutritional deficiencies, these risks may be mitigated during the reintroduction phase, and overall nutritional adequacy does not appear compromised, particularly when individualized dietary approaches are applied^56,57. Some studies report short-term reductions in caloric intake and micronutrients such as calcium and thiamine^39,63, whereas others demonstrate that adapted versions of the diet maintain adequate intake and improve overall dietary quality^49,64.

This review incorporated high-level evidence, including 15 randomized controlled trials and 7 systematic reviews with meta-analysis, all with control groups and a minimum duration of four weeks. Studies focused exclusively on adults diagnosed with irritable bowel syndrome and included a considerable total sample size of 1,315 participants across randomized controlled trials. Findings were consistent across studies and were evaluated using validated instruments for symptom severity, quality of life, and adherence, which contributed to a low risk of bias in most trials. The publication timeframe (2015-2024) further supports the relevance and contemporaneity of the evidence.

Nevertheless, several important limitations were identified. Variability in symptom measurement across studies was observed, along with limited information on adherence and lack of long-term outcome data due to the scarcity of prospective studies. In addition, limited cultural and geographic diversity, with predominance of European study populations, restricts generalizability of findings to other contexts, particularly Latin America. Although some studies describe dietary habits among patients with IBS in Latin America^45,65,66, further research is required to evaluate the effectiveness of the LFD in this geographic context and to identify dietary challenges specific to these populations. Furthermore, this systematic review was limited by heterogeneity in outcome definitions across included studies, which precluded quantitative synthesis through meta-analysis.

The LFD represents an effective strategy for IBS management, particularly when individualized according to patient subtype. Nutritional education and professional guidance are essential to ensure adherence. Although the diet improves quality of life and emotional symptoms, monitoring of nutritional intake remains necessary to prevent potential deficiencies. Effects on the intestinal microbiota appear mild and transient. Additionally, combination with complementary therapies such as cognitive behavioral therapy or yoga may enhance clinical benefits.

Conclusions

The low-FODMAP diet has demonstrated effectiveness in reducing gastrointestinal symptoms and improving quality of life in patients with irritable bowel syndrome. Its implementation is also associated with benefits in psychological well-being, including reductions in anxiety symptoms and dysphoria. These findings highlight the importance of promoting adequate dietary adherence, as well as the need for individualized management supported by professional guidance to maximize the clinical effectiveness of this dietary strategy.