Functional dyspepsia (FD) is a common disorder of the gut-brain interaction characterized by bothersome symptoms including postprandial fullness, early satiation, epigastric pain, and epigastric burning, without structural disease. Despite its frequency, the exact prevalence of FD remains poorly understood. There is a significant overlap of FD with other common gastrointestinal disorders, including irritable bowel syndrome (IBS), gastroparesis (GP), and gastroesophageal reflux disease (GERD). This review aims to explore the most studied dietary interventions for managing FD symptoms, including the low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP) diet, gluten-free diet (GFD), and traditional dietary advice (TDA). Furthermore, this review will discuss the efficacy of alternative nutrition therapies including STW-5, caraway oil, artichoke leaf extract, and ginger. To support clinical practice, this review will also provide clinical pearls and practical tools designed to enhance symptom management and optimize patient care for those living with FD.

What is Functional Dyspepsia? 

Dyspepsia is a Greek term: dys- (meaning “bad” or “impaired”) and pepsis (meaning “digestion”).¹ Although dyspeptic symptoms can be associated with an underlying organic pathology—such as peptic ulcer disease, gastroesophageal reflux disease, or malignancy — more than 75% cases have no organic cause and are therefore labeled as functional dyspepsia (FD).²

According to the Rome IV criteria, FD encompasses chronic or recurrent upper abdominal symptoms, including postprandial fullness, early satiation, epigastric pain, or burning, in the absence of structural disease that could explain these complaints.³ The Rome IV criteria further subdivide FD into two clinically meaningful subtypes—Postprandial Distress Syndrome (PDS) and Epigastric Pain Syndrome (EPS)—which reflect differences in symptom patterns, timing in relation to meals, and severity (See Table 1). While patients may exhibit overlapping features, identifying the subtype can guide management strategies.

Furthermore, symptoms of FD that extend beyond the ROME IV criteria tend to be specific to each subtype (See Table 2). Patients may not experience all the listed symptoms, but clear patterns differentiate EPS from PDS when assessed in this context.

Background and Statistics

Although FD is a common disorder of the gut-brain interaction (DGBI), little is known about its prevalence.⁴ A global systematic review and meta-analysis of 256,915 participants from 40 countries (1990–2022) found functional dyspepsia (FD) affected 7–12% of people.⁵The Rome criteria for diagnosing functional dyspepsia have become increasingly rigorous as subclassifications have evolved, making prevalence under Rome IV lower than under previous Rome iterations. Dyspepsia is more common in women, smokers, in developing countries vs. developed countries, and those taking non-steroidal anti-inflammatory drugs.^5,6 Dyspepsia is estimated to cost the United States healthcare service over $18 billion per annum and societal costs are likely to be double this with 2–5% of patients taking time off work because of symptoms.^7-8

Table 1. ROME IV Criteria for Functional Dyspepsia and Subtypes³

Functional Dyspepsia includes one or more of the following symptoms:

1. Bothersome postprandial fullness   2. Bothersome early satiation   3. Bothersome epigastric pain   4. Bothersome epigastric burning In the absence of structural disease that is likely to explain the symptoms. Symptoms must be chronic or recurrent, with onset at least six months prior to diagnosis and persistence for the previous three months.

Functional Dyspepsia is further classified into two subtypes: Postprandial Distress Syndrome (PDS) and Epigastric Pain Syndrome (EPS).3  PDS diagnosis must include one or both of the following for at least three days per week:    1. Bothersome postprandial fullness (i.e., severe enough to impact usual activities)   2. Bothersome early satiation (i.e., severe enough to prevent finishing a meal of usual size) EPS diagnosis must include one or both of the following at least 1 day per week:    3. Bothersome epigastric pain (i.e., severe enough to impact usual activities)   4. Bothersome epigastric burning (i.e., severe enough to impact usual activities)

Possible Overlap between Functional Dyspepsia and Other Gastrointestinal Disorders

Various research studies have been conducted over the years to explore the overlap among FD and other gastrointestinal disorders, including gastroesophageal reflux disease (GERD), irritable bowel syndrome (IBS), and gastroparesis (GP). 

Gastroesophageal Reflux Disease

FD and GERD often present with overlapping symptoms including upper abdominal bloating, epigastric pain, regurgitation, and heartburn.^9-10 A systematic review and meta-analysis examined the overlap between FD and GERD and found that 41.15% of patients with GERD also experienced FD symptoms. Similarly, 31.32% of patients with FD also experienced GERD-like symptoms.⁹ Research has shown that there is similarity in pathophysiological mechanisms as well. A well-known mechanism in FD, impaired gastric accommodation, has been associated with more frequent transient lower esophageal sphincter relaxation (TLESRs) episodes.⁹ Additionally, both impaired gastric accommodation and TLESRs can increase stomach pressure, promoting acid reflux.¹⁰ Other potential overlapping pathways include esophageal acid exposure, delayed gastric emptying, and visceral hypersensitivity.⁹

Irritable Bowel Syndrome

In a multicenter, 12-month longitudinal study involving 807 individuals diagnosed with IBS according to the Rome IV criteria, 208 participants (25.8%) had coexisting PDS, 60 (7.4%) had EPS, and 178 (22.1%) had both PDS and EPS.¹¹ Participants with IBS and PDS, as well as those with both PDS and EPS, reported a significantly greater impact on daily activities, defined as interference ≥ 50% of the time, compared to those with IBS alone (73.8% for IBS and PDS, 72.7% for IBS, PDS, and EPS, vs. 50.5% for IBS alone; p < 0.001). Patients with overlapping PDS and EPS were more likely to see their physician about their symptoms and underwent a higher number of IBS treatments compared to those with IBS alone.

Table 2. Other Symptoms of Postprandial Distress Syndrome and Epigastric Pain Syndrome 

Other Symptoms of PDS	Other Symptoms of EPS
Postprandial epigastric pain or burning	Pain may be induced by ingestion of a meal, relieved by ingestion of a meal, or may occur while fasting
Postprandial epigastric bloating	Epigastric bloating
Postprandial belching	Excessive belching
Postprandial nausea	Nausea

Gastroparesis 

GP is a neuromuscular disorder that is classified by delayed gastric emptying, with more than 60% of food remaining in the stomach at 2 hours and/or more than 10% at 4 hours.¹² Recent studies have shown that delayed gastric stomach emptying is also present in 25-37% of patients with FD.¹² Bloating, postprandial fullness, early satiety, and epigastric pain are symptoms commonly experienced by both patients with FD and GP; however, nausea and vomiting are hallmarks for GP alone.¹³ Pasricha et al.conducted a prospective study of 944 patients for 48 weeks to study the relationship between FD and GP.¹⁴ Out of the total patients, 720 (76%) were diagnosed with GP and 224 (24%) with FD. By 48 weeks, 41% of patients had a revised diagnosis: 42% of those initially diagnosed with GP were reclassified as FD, whereas 37% with FD initially were now diagnosed with GP.This diagnostic shift reflects the clinical overlap between these two disorders and the hypothesis that gastric emptying studies alone may not be an accurate marker for distinguishing between the two.

Self-Reported Dietary Triggers

In a study of over 200 patients with FD, an increase in all FD symptoms occurred within 15 minutes of eating a meal in 79% of patients, showing that diet is a significant contributor to symptoms.¹⁵ Studies on self-reported food and lifestyle triggers show that fatty foods, acidic foods, spicy foods, wheat products, watermelon, and fruit juices are the most common reported.¹⁶  However, some studies suggest that spicy foods may actually improve symptoms. In a small randomized controlled trial of 30 individuals with functional dyspepsia, red pepper powder significantly improved overall symptom scores, including reductions in epigastric pain, fullness, and nausea compared to placebo.¹⁷ In a cross-sectional survey of 121 patients with FD, 55% listed FODMAPs as the most reported trigger which included wheat, fruit juices, and watermelon.¹⁸

Current Evidence from Studied Diet Interventions

There have been several dietary approaches explored for the treatment of FD including the  traditional dietary advice (TDA), gluten-free diet (GFD), and the low FODMAP diet (LFD), though evidence at this time is limited.

Traditional Dietary Advice

The recommendations under TDA include eating small, frequent meals, avoiding perceived dietary triggers such as alcohol, caffeine, chocolate, spicy or acidic foods, and high-fat foods, consuming food slowly and chewing thoroughly, and not eating 3 hours before bed. Recent research has explored the relationship between symptom exacerbation and some of the foods listed above, including high-fat food and spicy foods. High-fat foods have been shown to delay gastric emptying, impair gastric motility, and increase post-meal fullness in patients with FD.¹⁹

Capsaicin, the chemical compound found in higher concentrations in chili peppers, has been shown to lead to more symptoms in individuals with FD when compared to healthy controls or placebo.¹⁹ Capsaicin activates the transient receptor potential vanilloid-1 (TRPV1) receptors, leading to a burning sensation. Capsaicin can also result in chemical hypersensitivity, which can trigger upper gastrointestinal symptoms in individuals with FD.²⁰ The genetic variation of the TRPV1 gene, G315 polymorphism, is inversely correlated with FD, though research has shown that gene variations were unable to predict the severity of FD symptoms based on questionnaires.

Gluten-Free Diet

Hosseinian et al. conducted a systematic review including information on the impact of gluten on FD symptoms across 27 studies, with a meta-analysis on 5 RCTs.²¹ The meta-analysis showed that there was a statistically significant increase in the severity of epigastric pain (weight mean difference (WMD) = 0.46; 95% CI), bloating (WMD = 0.67; 95% CI), and early satiety (WMD = 0.91; 95% CI) following gluten-consumption of 0.5-32 gram per day.²¹ These findings suggest relief of FD symptoms associated with avoiding or reducing gluten. Refractory functional dyspepsia (RFD) is defined by symptoms that continue despite medical interventions or Helicobacter pylori (H. pylori) eradication. 

The presence of non-celiac gluten sensitivity (NCGS) in 77 patients with RFD was investigated in a randomized, double-blind, placebo-controlled trial.²² Each patient followed the GFD for 6 weeks, in which 27 patients (35%) showed symptom improvement. Of the 27 patients that were then assigned to a gluten or placebo challenge, 5 patients (6.4% of the total sample) reported intestinal and/or extra intestinal symptoms after gluten exposure. The most common symptoms reported included postprandial fullness (100%), epigastric pain/burning (80%), fatigue (80%), headache (80%), and musculoskeletal pain (60%). Patients were monitored for three months following the study and three additional patients reported symptom recurrence with gluten consumption. Due to the overlap seen between NCGS and FD, the GFD may be an effective dietary recommendation in symptom management for a subset of patients with FD in which there is a clinical concern for NCGS.²²

Low Fodmap Diet 

In a single-blind prospective study, Goyal et al.evaluated the efficacy of the LFD and TDA.²³ During the study, the Short-Form Nepean Dyspepsia Index (SF-NDI) was used to measure symptomatology in 105 patients with FD (54 assigned to LFD, 51 assigned to TDA), with each subject completing either one of the two diets for 4 weeks (phase I). The participants following the LFD were then advised to follow the reintroduction phase of the LFD for 4-12 weeks (phase II). The baseline SF-NDI scores improved significantly with both diets (LFD: 66.7% improvement [36/54]; TDA: 56.9% improvement [29/51]; p = 0.32). Patients with bloating and PDS had significantly greater improvements with the LFD versus TDA at 4 and 12 weeks (p = 0.04), despite improvements in overall symptomatology in both diets.²³ While not statistically significant, there was a trend towards improvement in EPS patients with TDA. 

The effectiveness of the LFD was compared to standard dietary advice (SDA), like the recommendations under TDA, in an observational study.²⁴ Of the 59 patients with FD, 40 followed the LFD and 19 were assigned to SDA. The Structured Assessment of Gastrointestinal Symptoms (SAGIS) was used to collect data on epigastric and overall gastrointestinal symptoms. The results showed a greater reduction in epigastric scores in the LFD compared to SDA (p = 0.032). Additionally, there were greater reductions in postprandial pain, excessive belching, and bloating in the LFD (p < 0.05). When looking at overall gastrointestinal symptoms, there was statistically significant improvement in the LFD group compared with the standard dietary advice (p = 0.026). 

Preliminary results seen in an abstract from the University of Leuven showed that 62% of 25 patients with FD experienced a statistically significant improvement in symptoms following a 6-week low FODMAP diet. Improvements were observed in both overall and individual symptom scores, including upper abdominal bloating, early satiety, and postprandial fullness. Following the 6-week intervention, patients followed a blinded reintroduction phase, which revealed variability in the specific FODMAPs that triggered symptom recurrence. Mannitol and galacto-oligosaccharides triggered symptom recurrence in 29% of the patients, followed by fructans (21%), sorbitol (14%), fructose (14%) and lactose (12%).²⁵ It is important to note that fructans are found in many gluten-containing grains. Researchers who have studied the GFD in FD have noted that it is not clear whether fructans or gluten is the culprit for triggering dyspeptic symptoms.²¹

Complementary and Alternative Therapies 

According to American College of Gastroenterology (ACG) and the Canadian Association of Gastroenterology (CAG) guidelines, the quality of evidence supporting complementary and alternative nutrition therapies for FD management is of poor quality.²⁶ The available evidence on the therapeutic benefits of caraway oil, STW5, artichoke leaf extract, and ginger in management of FD will be reviewed.

Caraway Oil

Caraway oil has been hypothesized to increase gastric accommodation, and L-menthol is an antispasmodic whose action includes modulation of gastric sensory nerves, thereby promoting smooth muscle relaxation. The combination of these agents may exert a prokinetic effect and reduce visceral hypersensitivity. A meta-analysis and systematic review of five randomized controlled trials involving 578 patients showed that the combination of caraway oil and L-menthol resulted in statistically significant improvement in overall FD symptoms, specifically with a reduction in epigastric pain. While these results are promising, limitations identified from this study include a short treatment duration of only four weeks, an insufficient sample size to be able to evaluate publication bias adequately, and potential differences in patient diagnosis due to the lack of using validated criteria among all studies.²⁷It should be noted that peppermint is not appropriate for all patients, including those with hiatal hernia, GERD, gallbladder disorders, and those that are pregnant and lactating.^28,29

STW-5

Efficacy of STW-5, a nine-herb preparation, was tested in an 8-week double-blind, placebo-controlled RCT of 315 patients with FD. In the treatment group, the therapeutic effect was seen as early as within 2 weeks, with symptom improvement of 57%, which increased to 86% by week 4. However, the number of responders in the placebo group was similar to the STW-5 group, respectively 72.2% versus 78.3%. Overall, in comparison to the placebo group, the GIS score improved significantly in the STW-5 group during the course of treatment (p < 0.05).³⁰ Furthermore, a meta-analysis of three RCTs demonstrated that STW-5 provided a statistically significant benefit over placebo in reducing postprandial fullness, early satiety, and epigastric pain.³¹ It should be noted that case reports of liver injury with use of this product have been reported and close monitoring with a medical professional is recommended if considering use of STW-5.³²

Artichoke Leaf

Artichoke (Cynara scolymus) leaf extract (ALE), long used for dyspepsia, has been shown to have lipid-lowering, antioxidant, and antispasmodic effects. The effectiveness of ALE in managing FD was evaluated in a six-week, double-blind, placebo-controlled study involving 247 patients with FD. Participants received either ALE preparation or a placebo, and the effectiveness of ALE was assessed using a four-point patient-rated scale of overall symptom change. Dyspeptic symptoms and quality of life were also evaluated using the Nepean Dyspepsia Index (NPI). After six weeks, the ALE group showed significantly greater symptom improvement than placebo (p < 0.01), with notable reductions in early satiety, flatulence, and fullness compared to placebo (all p < 0.05), and enhanced quality of life scores (p < 0.01).³³ However, evidence is too limited at this time to make clinical recommendations. 

More recently, the effectiveness of ALE in the management of FD has been evaluated in combination with ginger (Zingiber officinalis). In addition to its well-known anti-nausea and antiemetic effects, ginger has also been shown to enhance gastric motility. The efficacy of a combination of ALE and ginger was explored in a 4-week, double-blind, placebo-controlled trial including 126 adults diagnosed with FD. Participants took two capsules daily; 65 received the supplement containing ginger and ALE, while 61 received the placebo. After two weeks, there were significant improvements in FD symptoms in the supplementation group compared to the placebo group (p = 0.017). These results remained consistent at the 4-week mark. Specifically, there were significantly greater improvements in nausea, epigastric fullness, epigastric pain, and bloating in the supplementation group when compared to the placebo (p < 0.001, p < 0.001, p < 0.002, p = 0.017, respectively).³⁴ 

Ginger

Ginger alone also has been studied in the context of stomach emptying, with results showing that 3 pills daily equaling 1200mg could increase gastric emptying and stimulate antral contractions, though its impact on FD symptoms is conflicting.^35-36 In all but one of the studies, there were no adverse events noted. In the oldest of the studies, adverse events were classified as gastrointestinal, identified as mild to moderate and resolved on their own by the end of the study. 

Practical Applications

When selecting dietary or complementary interventions for FD, tailoring recommendations to the patient’s specific symptom profile can improve effectiveness. The following points highlight how current evidence can guide clinical decision-making:

Patients experiencing bloating and PDS may benefit more from an LFD than a TDA.

Individuals with postprandial pain, excessive belching, and bloating are the most likely to experience meaningful symptom relief from an LFD.

Given the overlap between NCGS and FD, a GFD may help manage symptoms in patients for whom NCGS is a clinical concern.

Although evidence is not statistically significant, patients with EPS may notice some improvement with a TDA.

Caraway oil, based on limited data, may reduce FD symptoms—particularly epigastric pain.

STW-5 may help alleviate postprandial fullness, early satiety, and epigastric pain; however, it may not be appropriate for all patients and has been linked to possible liver-related adverse effects.

Ginger and artichoke extracts may provide relief for FD symptoms; however, current evidence is limited and insufficient to support routine clinical use. 

References

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