Mediterranean diet provides significant relief for IBS sufferers, study finds

Living with irritable bowel syndrome can often feel like a delicate balance between food and fear. One day, a simple meal might provide comfort, while the next, that same meal might result in cramping, bloating, and anxiety that causes you to question every bite. For millions, this is the reality of living with IBS - a syndrome that is experienced by approximately 4-11% of the global population, and rarely with easy fixes.

For years, there has been one gold-standard diet, the low-FODMAP diet, which removes a number of fermentable carbohydrates in the gut, in order to improve irritable bowel syndrome symptoms. About half of those who try the diet have symptom relief from the diet; however, the restriction is often limiting. Many of the items removed are often enjoyed daily. As a result, people often find themselves feeling trapped between transitional comfort and restrictive distress, worrying not only about the potential loss of comfort but also the loss of pleasure in eating.

Amidst the frustrations, researchers at the University of Michigan were wondering if there was a means of looking at a dietary approach that could lead to gut peace, or at a minimum, limit the burden of daily transition and removal of high-FODMAP foods.

The research team was led by gastroenterologist Dr. Prashant Singh with the assistance of Dr. William Chey, chief of Gastroenterology at Michigan Medicine. The first randomized controlled trial was initiated, assessing the Mediterranean and low-FODMAP diets as a dietary intervention for irritable bowel syndrome.

The study results were published in Neurogastroenterology & Motility and have contributed to a new understanding of how food not only influences physical comfort but also emotional well-being. The Mediterranean diet emphasizes the consumption of a variety of fruits and vegetables, legumes, olive oil, whole grain sources, and low-fat protein (fish and chicken).

The low-FODMAP intervention reduces the amount of specific carbohydrate groups that are able to ferment in the gut and produce gas. The two dietary strategies were developed and provided using a meal delivery service, called ModifyHealth, which ensured participants adhered to each study diet throughout the duration of the study.

In total, participants received all of their meals and snacks for a period of four weeks and were instructed not to eat anything aside from what they had received from the study for the duration of the study.

Participants included adults, aged 18-70 years, who met a diagnosis of irritable bowel syndrome (IBS) with diarrhea or mixed bowel habits. Additionally, all participants reported experiencing at least a moderate level of abdominal pain in the week prior to enrollment. Candidates were excluded for having other digestive conditions, eating disorders, or if they had taken antibiotics within 3 months of participation to ensure the data remains clean.

On each day of the study, participants reported their level of abdominal pain and bloating on an 11-point scale, and each week, participants self-reported on their overall symptom severity. Evaluators, who were blinded to the study conditions, measured change in anxiety and quality of life using validated survey instruments.

To achieve the primary outcome variable of this study, participants were required to demonstrate at least a 30% reduction in symptom severity scores of abdominal pain for two weeks or more as per the United States Food and Drug Administration recommendations for clinical and investigational research related to IBS.

Out of 26 participants initially recruited into the study, 20 participants completed the trial, with 10 per group. Participants left for several reasons, including worsening symptoms and/or choosing to leave for personal reasons. Both groups had excellent compliance with the prescribed (provided) diet, at nearly 94%. Research teams reported that any differences uncovered were due to the diets and not the degree of compliance of the participants.

Overall, the results were encouraging. Approximately 73% of the participants on the Mediterranean diet reached the primary outcome of a 30% reduction in abdominal symptoms, compared to 81.8% in the low-FODMAP diet. While this difference was not statistically significant, it is important to note that both diets produced a clinically meaningful result.

When researchers compared the groups more closely, the clear winner in providing greater overall symptomatic relief was the low-FODMAP diet.

When participants were asked to complete a questionnaire that measured symptom severity, the average score was reduced by 105.5 points in the low-FODMAP diet compared to 60 points in the Mediterranean diet. Moreover, more than 50% of low-FODMAP participants reported they experienced adequate overall relief, while only 25% in the group following the Mediterranean diet reported the same outcome.

In regard to other abdominal indicators, the Mediterranean group reported reductions in abdominal pain, bloating, and discomfort at about 40%, demonstrating that compliance differences related to strictness can produce meaningful improvements.

The implications of IBS may be about more than just physical symptoms: the mind-gut connection. Irritable bowel syndrome rarely exists in a vacuum; anxiety, stress, and quality of life are all complexly related to this disorder. In fact, in this study, individuals in the low-FODMAP diet group had a 4-point reduction in anxiety scores, while individuals in the Mediterranean diet group had almost no change in scores at all. Quality of life improvements were slight in the low-FODMAP group and decreased slightly in the Mediterranean group. Overall, there were no differences between groups.

Nonetheless, the results suggest a dietary influence on comfort and mood. Living with IBS can affect someone’s mental health, and if there is an intervention that can restore just a bit of confidence about what to eat at mealtimes, it can alleviate that mental burden.

While both diets may have the same or similar benefits, they may potentially accomplish them in different ways. The low-FODMAP type diet may remove fermentable carbohydrates that are used as a substrate for bacteria to produce gas when they ferment carbohydrates, which would relieve bloating and cramping. The Mediterranean diet does not remove foods; rather emphasizes anti-inflammatory, nutrient-rich foods to nourish the intestinal lining and encourage diversity and balance among gut bacteria.

Importantly, the two dietary patterns probably have an opposing effect in changing the gut microbiome. The low-FODMAP diet likely decreases the presence of some beneficial bacteria, while Mediterranean diets will likely increase bacteria. This may help explain why some patients are successful with one diet, while others are successful with another diet.

Dr. Singh and her colleagues presented their results as “hypothesis-generating”. They do not think the study is the last word on the topic, as it only included 26 participants over a four-week period. However, it provides the platform upon which larger, longer studies can be developed to help clinicians individualize patient treatment for IBS based on their lifestyles and gut health.

"Restrictive diets like the low-FODMAP diet can cause challenges for patients,” Dr. Singh said. “They can be time-consuming, expensive, and there are concerns regarding deficiencies in the diet. The Mediterranean diet was appealing to us because it didn't eliminate foods and did not have some of those drawbacks."

Dr. Chey similarly stated, "The results of this study were added to a growing body of literature supporting the Mediterranean diet as a healthy and evidence-based option to treat IBS."

While the low-FODMAP diet remains a more intense management plan for most patients, the Mediterranean diet may be a more sustainable, healthy, and care plan.

Research findings are available online in the journal Neurogastroenterology & Motility.

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