Adopting either a low FODMAP diet or one that was low in carbohydrates but still high in fibre relieved irritable bowel syndrome (IBS) symptoms more effectively than medication over a four-week trial, researchers have suggested.
Two kinds of diet seem to work better than taking medication in addressing IBS, they wrote in The Lancet, finding that either the low FODMAP option or one that was low in carbohydrates – but still high in fibre – relieved IBS symptoms more effectively over the trial
FODMAPs is a group of sugars and similar carbohydrates found in dairy, wheat and certain fruits and vegetables. The second diet was a less common approach used for IBS: an adapted low-carb diet that is high in fibre but low in all other kinds of carbohydrates, namely sugar and starch.
In the randomised trial, both diets led to better improvements in symptoms than standard treatment with medicines after four weeks, reports New Scientist.
IBS can cause a puzzling range of symptoms, including diarrhoea, constipation, bloating and abdominal pain, which can wax and wane over time. The root cause of the condition is unclear.
The usual advice is to avoid common triggers, such as caffeine, alcohol or spicy food. People may also take symptomatic treatments, such as laxatives for constipation or medication for diarrhoea.
If those measures don’t work, people may also try reducing food high in FODMAPs, which are thought to contribute to bloating and diarrhoea because they tend to go undigested until they reach the colon.
This encourages water retention by the colon and produces gas as the molecules are consumed by bacteria, which contributes to bloating.
Sanna Nybacka at the University of Gothenburg in Sweden and her colleagues wanted to see how the usual low-FODMAP diet stacked up against the different approach of low-carbing while still eating plenty of fibre.
In practice, this meant eating high-fat and high-protein food, such as meat and dairy products, while fibre sources included nuts, seeds, beans and vegetables, like cabbage.
The team asked about 300 people with IBS to use one of three approaches: taking medicines as needed for their symptoms or adopting either of the two diets. For the dietary approaches, people were sent free grocery deliveries, as well as given detailed meal plans and recipes.
After a month, 76% of those in the low-FODMAP group reported a significant reduction in their symptoms, compared with 71% of those on the low-carb diets and 58% in the medical treatment group.
The big surprise was that a low-carb, high-fibre diet, which didn’t exclude FODMAP-containing food, was about as effective as a low-FODMAP approach, said Nybacka.
“We cannot provide any answers to why that is. It seems as if modifying the carbohydrate contents and lowering the FODMAP intake might be beneficial.”
But Hazel Everitt at the University of Southampton in the UK says the trial would have been more useful if it had lasted longer. “The problem with many proposed IBS diets are that they are very difficult to maintain long term,” she said.
The participants were followed for up to six months, but for the last five months, those offered the medication approach initially were also given dietary advice.
Nybacka says one potential problem with the low-carb, high-fibre diet is that those in this group saw a small rise in their blood cholesterol levels. People should therefore seek their doctor’s advice before adopting this diet, she suggests.
Study details
A low FODMAP diet plus traditional dietary advice versus a low-carbohydrate diet versus pharmacological treatment in irritable bowel syndrome (CARBIS): a single-centre, single-blind, randomised controlled trial
Sanna Nybacka, Hans Törnblom, Lena Böhn et al.
Published in The Lancet on 18 April 2024
Summary
Background
Dietary advice and medical treatments are recommended to patients with irritable bowel syndrome (IBS). Studies have not yet compared the efficacy of dietary treatment with pharmacological treatment targeting the predominant IBS symptom. We therefore aimed to compare the effects of two restrictive dietary treatment options versus optimised medical treatment in people with IBS.
Methods
This single-centre, single-blind, randomised controlled trial was conducted in a specialised outpatient clinic at the Sahlgrenska University Hospital, Gothenburg, Sweden. Participants (aged ≥18 years) with moderate-to-severe IBS (Rome IV; IBS Severity Scoring System [IBS-SSS] ≥175) and no other serious diseases or food allergies were randomly assigned (1:1:1) by web-based randomisation to receive a diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) plus traditional IBS dietary advice recommended by the UK National Institute for Health and Care Excellence (hereafter the LFTD diet), a fibre-optimised diet low in total carbohydrates and high in protein and fat (hereafter the low-carbohydrate diet), or optimised medical treatment based on predominant IBS symptom. Participants were masked to the names of the diets, but the pharmacological treatment was open-label. The intervention lasted 4 weeks, after which time participants in the dietary interventions were unmasked to their diets and encouraged to continue during 6 months’ follow-up, participants in the LFTD group were instructed on how to reintroduce FODMAPs, and participants receiving pharmacological treatment were offered diet counselling and to continue with their medication. The primary endpoint was the proportion of participants who responded to the 4-week intervention, defined as a reduction of 50 or more in IBS-SSS relative to baseline, and was analysed per modified intention-to-treat (ie, all participants who started the intervention). Safety was analysed in the modified intention-to-treat population.
Findings
Between Jan 24, 2017, and Sept 2, 2021, 1104 participants were assessed for eligibility and 304 were randomly assigned. Ten participants did not receive their intervention after randomisation and thus 294 participants were included in the modified intention-to-treat population (96 assigned to the LFTD diet, 97 to the low-carbohydrate diet, and 101 to optimised medical treatment). 241 (82%) of 294 participants were women and 53 (18%) were men and the mean age was 38 (SD 13). After 4 weeks, 73 (76%) of 96 participants in the LFTD diet group, 69 (71%) of 97 participants in the low-carbohydrate diet group, and 59 (58%) of 101 participants in the optimised medical treatment group had a reduction of 50 or more in IBS-SSS compared with baseline, with a significant difference between the groups (p=0·023). 91 (95%) of 96 participants completed 4 weeks in the LFTD group, 92 (95%) of 97 completed 4 weeks in the low-carbohydrate group, and 91 (90%) of 101 completed 4 weeks in the optimised medical treatment group. Two individuals in each of the intervention groups stated that adverse events were the reason for discontinuing the 4-week intervention. Five (5%) of 91 participants in the optimised medical treatment group stopped treatment prematurely due to side-effects. No serious adverse events or treatment-related deaths occurred.
Interpretation
Two 4-week dietary interventions and optimised medical treatment reduced the severity of IBS symptoms, with a larger effect size in the diet groups. Dietary interventions might be considered as an initial treatment for patients with IBS. Research is needed to enable personalised treatment strategies.
See more from MedicalBrief archives:
High-fat diet with antibiotic use linked to gut inflammation