A new study in Scientific Reports shows that a low-FODMAP diet can improve IBS symptoms in adults, but nutritional deficits raise the stakes for long-term use without dietitian support.
Study: The effect of low-FODMAP diet on patients with irritable bowel syndrome. Image Credit: Lightspring / Shutterstock
In a recent article published in the journal Scientific Reports, researchers investigated the effectiveness of a dietary intervention low in fermentable oligo-, di-, mono-saccharides, and polyols (FODMAPs) for improving irritable bowel syndrome (IBS) symptoms in adult patients in Saudi Arabia.
Their findings indicate that most participants reported a shift from severe symptoms to moderate symptoms, with a small proportion reaching mild status after the intervention, representing a marked improvement in the severity of their condition. The overall proportion of severe cases decreased from 17.8% to 14%, the moderate group increased from 82.2% to 86%, and 14% of participants reported mild symptoms after the intervention. This indicates improvement in symptom categories, but a majority remained moderate. However, the restrictive diet could pose risks related to weight changes and specific nutrient deficiencies, including riboflavin and vitamin C. Other nutrients such as calcium, magnesium, and iron also declined, reflecting potential broader nutritional risks.
Background
IBS is a chronic gastrointestinal disorder marked by changes in bowel habits and abdominal pain. Affecting between 9% and 23% of the global population, with a predominance in women. Based on stool patterns, doctors classify IBS into diarrhea-predominant (IBS-D), constipation-predominant (IBS-C), and mixed-type (IBS-M).
Beyond gastrointestinal symptoms like bloating, constipation, or diarrhea, IBS can also affect a person’s physical, emotional, and social well-being, contributing to anxiety, depression, and reduced quality of life.
The diagnosis of IBS is often made using the Rome criteria (in this study, the Rome III criteria were used, as many participants had been previously diagnosed under this framework and it was the predominant tool in regional clinical practice), based on guidelines, symptom timeframes, and special symptoms that doctors might expect to see. Treatment typically begins with lifestyle and dietary modifications.
Many IBS patients report worsening symptoms after eating, prompting increased interest in dietary management strategies. Research shows that fermentable carbohydrates, known as FODMAPs, may worsen symptoms due to their poor absorption and fermentation in the gut, leading to bloating, gas, and diarrhea.
A diet low in FODMAPs restricts foods containing fermentable sugars and has been shown to reduce symptoms and improve the quality of life of those with IBS. However, despite increasing use in clinical settings across Saudi Arabia, there are no national dietary recommendations tailored to local eating habits.
About the study
In this study, researchers examined the effect of low-FODMAP diets on symptom severity among adult IBS patients in the city of Jeddah in Saudi Arabia. The intervention took place over 10 weeks and included 45 participants between the ages of 18 and 45, 33 of whom were female, seeking care at outpatient clinics.
Eligible participants had received medical diagnoses of moderate or severe IBS-M or IBS-D, a normal body mass index (BMI), and were not using medications, supplements, or herbal remedies. Individuals with other chronic illnesses, prior abdominal surgery, obesity, or pregnancy were excluded.
The study began with a pilot involving 20 participants to validate the clarity of the questionnaires. All participants gave informed consent and completed the IBS Symptom Severity Scale (IBS-SSS) and a demographic and food frequency questionnaire adapted to local foods and translated into Arabic.
The dietary intervention had two phases: a six-week restriction phase during which high-FODMAP items were eliminated, followed by a four-week reintroduction phase during which specific food triggers were identified.
Sessions were held via video call, and monitoring was done through messaging applications. Anthropometric data (height and weight) were collected to calculate BMI. After the program, symptom severity was reassessed.
Dietary intake data were self-reported using a Food Frequency Questionnaire, which the authors note is subject to recall bias. Data were analyzed using statistical comparisons such as t-tests and chi-squared tests to assess differences and associations.
Findings
Nearly 70% of the participants were female, and individuals aged between 18 and 30 accounted for 66.7%. Most were married (62.2%), and slightly over 42% earned less than 5,000 riyals each month.
After following a low-FODMAP diet for 10 weeks, participants experienced a significant improvement in IBS symptoms. The average IBS-SSS score dropped from 290 to 190. Notably, the percentage of patients with severe symptoms decreased from 17.8% to 14%, while the moderate group increased from 82.2% to 86%, and 14% reached the mild category.
There was also a significant decrease in daily intake of calories, carbohydrates, fats, starches, sugars, and fibers. The most notable reductions were in carbohydrates, fat, and sugars. FODMAP intake also declined significantly, especially fructo-oligosaccharides, excess fructose, and lactose. There were also statistically significant decreases in specific nutrients, including riboflavin and vitamin C. Calcium, magnesium, and iron intakes also declined.
Gender and age influenced FODMAP consumption before the intervention, with females consuming more lactose and fructo-oligosaccharides than males. However, after the intervention, while some gender differences in FODMAP intake were no longer significant, differences for certain FODMAPs, such as excess fructose and mannitol, persisted or emerged.
Younger participants (18–30) had a higher proportion of above-average mannitol and galactooligosaccharides intake post-intervention, while older participants (31–45) had higher intakes of lactose and fructose both before and after the intervention for lactose and after the intervention for fructose.
These findings show that the dietary intervention effectively reduced both IBS symptoms and FODMAP intake across different demographic groups. However, age- and gender-related variations in specific FODMAP intakes persisted for some items after the intervention.
Conclusions
Researchers noted that, as expected, IBS was more common in females and younger adults, likely due to hormonal, psychological, and lifestyle factors. They also observed that lower income and marital status could be linked to increased IBS prevalence.
The low-FODMAP diet significantly reduced symptom severity and intake of carbohydrates, sugars, and FODMAPs, supporting previous research that FODMAPs contribute to IBS symptoms through malabsorption and fermentation in the gut.
Strengths of the study include detailed nutrient analysis and assessment of demographic factors. Limitations include possible nutritional deficiencies due to reduced food variety, the use of self-reported dietary intake subject to recall bias, difficulty in recruiting participants, and the short duration of follow-up. The study also acknowledged the extensive length of the questionnaire, which might have deterred some participants, and noted that the Food Frequency Questionnaire (FFQ) may not fully capture daily variations in food intake. Gender- and age-related differences in dietary behavior also suggest the need for personalized guidance.
In conclusion, a 10-week low-FODMAP diet may help reduce IBS symptoms, but long-term adherence should be supported by professional nutrition advice to avoid nutrient imbalances. Future studies should focus on sustaining dietary changes and long-term effects.