Patients who had been referred to the gastroenterology department of Stord Helse-Fonna Hospital (Stord, Norway), and who fulfilled the Rome III criteria for the diagnosis of IBS were considered for inclusion in the study. Although both genders were able to participate, the patients were required to be between 18 and 69 years of age. Exclusion criteria comprised the presence of organic gastrointestinal disease, clinically significant systemic diseases, pregnancy or lactation, drug abuse, serious psychiatric diseases and collaboration issues. In addition, with the exception of appendectomy, cesarean section and hysterectomy, patients who had undergone abdominal surgery were excluded. This study was performed in accordance with the Declaration of Helsinki and was approved by the Regional Committee for Medical and Health Research Ethics West, Bergen, Norway. All patients provided oral and written consent to participate.

In total, 46 patients were included in the study. This included 35 females and 11 males with a mean age of 35 years (range, 18–69 years). Of these, 21 reported diarrhea (IBS-D), 18 reported constipation (IBS-C) and seven reported a mixture of both symptoms (IBS-M) as the predominant symptom of IBS. The patients underwent a complete physical examination, a gastroscopy with duodenal biopsies, a colonoscopy with segmental biopsies and several blood tests to exclude other organic causes for their symptoms. Each patient received three sessions of individual guidance on dietary management from a registered nurse with a specific education in IBS diet, with each session lasting ~45 min. The patients were asked to complete the following questionnaires before and ≥3 months subsequent to receiving the dietary guidance: The Birmingham IBS symptom score questionnaire, the IBS-Quality of Life (IBS-QOL) questionnaire, the Norwegian version of the Short-Form Nepean and Dyspepsia Index (SF-NDI) questionnaire and the MoBa Food Frequency Questionnaire (MoBa FFQ).

Each patient attended three 45 min sessions with a registered nurse with special training in the IBS diet, and seven years experience of providing dietary guidance to patients with IBS. The sessions were scheduled with intervals of ≥2 weeks between them. The information at the sessions was provided orally, and using charts and illustrative drawings. Written information was also supplied.

In the first session, the patient received general information with regard to the importance of regular meals and healthy eating habits, along with the effect of the diet on the development of symptoms. Emphasis was placed on the role of poorly absorbed, highly fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAPs), although patients were also informed of the effects of soluble and insoluble dietary fibers. It was emphasized that milk and dairy products were not triggers for IBS symptoms, and that the patients should consume dairy products daily. The patient was asked to keep a diary in which they recorded the time of eating/drinking, and the types of food and drinks they ingested daily. In addition, they were asked to report the occurrence of abdominal pain, abdominal distention and bloating, as well as stool frequency and consistency. The patients were instructed to try protein-, fat-, and carbohydrate-rich/poor diets and report the symptoms for each in the diary. This was performed over a 2-week period.

In the second scheduled session, the information provided in the first session was summarized, before the diary was examined to determine which food items may be triggering the patient’s symptoms. The patients were then advised to avoid these items and other items that were rich in FODMAPs and insoluble fibers, such as onions, garlic, paprika, cabbage, carbonated beverages, ‘lite’ products (those containing artificial sweeteners), bananas, beans and peas. The patient was asked to replace wheat and wheat products with spelt and spelt products, respectively, and was provided with a list of vegetables and fruits that contained lower levels of FODMAPs and insoluble fibers (18). The patients were also instructed to avoid the intake of food items supplemented with probiotics during the course of the study.

During the third and final session, the patient’s experience regarding the management of their diet was discussed with the nurse, so that the patient and nurse were then able to utilize this information to design a suitable diet for the patient to follow.

The Birmingham IBS symptom score questionnaire was developed to measure the symptoms of patients with IBS. It is disease-specific, acceptable to patients and suitable for self-completion. Its dimensions have been demonstrated to have good reliability, external validity and sensitivity (22). The Birmingham IBS symptom score questionnaire consists of 11 questions based on the frequency of IBS symptoms. The responses to the questions are measured on a six-point Likert scale, ranging from 0 (none of the time) to 5 (all of the time). The questionnaire has three underlying dimensions: pain (three items), diarrhea (five items) and constipation (three items), with lower scores indicating improved symptoms.

The quality of life in patients with IBS was assessed by the IBS-QOL and SF-NDI questionnaires.

The IBS-QOL questionnaire is a 34-item, IBS-specific quality of life measure that assesses physical and psychosocial functioning as a result of IBS (23,24). The questionnaire comprises eight domains; dysphoria, interference with activity, body image, health concerns, food avoidance, social reaction, sexual function and impact on relations. Responses are provided on the following five-point Likert scale: not at all, slightly, moderately, quite a lot and extremely.

The SF-NDI questionnaire is a disease-specific measure of the health-related quality of life (HRQoL), with 10 questions divided into five subscale scores (tension, interference with daily activities, disruption to regular eating/drinking, knowledge towards/control over disease symptoms and interference with work/study). Each question has five options, ranging from 1 (not at all) to 5 (extremely); thus, the total score ranges from 10–50, as per the developer’s original calculation formula, with higher scores indicating worse functioning or symptoms. This questionnaire was constructed and validated primarily in patients with dyspepsia (25). A Norwegian translation of the questionnaire was validated and demonstrated to perform well in patients with IBS (26).

Dietary intake was assessed using a semi-quantitative, self-administered food frequency questionnaire (MoBa FFQ). The MoBa FFQ asks participants to report the frequency of consumption and portion size of certain items over a defined period of time. Each item is defined by a series of foods or beverages. Additional questions on food purchasing and preparation methods enable the analysis software to further refine nutrient calculations. The MoBa FFQ used in this study was developed and validated by the Norwegian Institute of Public Health in Oslo, Norway (27,28). It enquires about the intake of 225 food items, grouped according to typical Norwegian meal patterns, and is designed to capture the dietary habits of the participant over a defined period, including the intake of any oral supplements. Analysis of the obtained data provides information concerning the intake of energy, water, macronutrients, micronutrients, minerals and alcohol, in addition to 100 specific food groups and items. It also yields information regarding meal patterns.

The paired t-test was used to analyze the data. The data are presented as the mean ± SEM values, and P<0.05 was considered to indicate a statistically significant difference.

Of the 46 patients recruited to this study, 18 abandoned the study; one was excluded due to non-compliance and one due to cooperation problems; four became better following the dietary guidance sessions, and then lost interest in and motivation for completing the study; two were diagnosed with celiac disease; one was diagnosed with lupus; one became pregnant and one moved abroad during the study. Thus, 17 of the original 46 patient cohort completed the study. These patients comprised 12 females and five males with a mean age of 34 years (range, 20–45 years); six of the 17 were IBS-D, eight were IBS-C and three were IBS-M. The time taken between receiving dietary guidance and completing the second set of questionnaires ranged from 3–9 months (median, 4 months).

The total scores of the Birmingham IBS symptom score questionnaires before and subsequent to receiving dietary guidance were 41.47±1.62 and 35.71±1.12, respectively. The reduction in symptoms was statistically significant (P=0.001). All three of the questionnaire dimensions (i.e., abdominal pain, diarrhea and constipation) were also reduced following the dietary guidance sessions; however, the result for constipation was not statistically significant (Fig. 1).

The total IBS-QOL score increased significantly from 125.4±4.2 to 136.8±3.8 following the dietary guidance sessions (P=0.003). This improvement was statistically significant in all domains, with the exception of the impact on relations (Fig. 2 and Table I).

The total SF-NDI scores (which reflect the reduction in HRQoL) before and following the dietary guidance sessions were 29.1±2.2 and 20.2±1.5, respectively. This improvement in HRQoL was statistically significant (P=0.002; Fig. 3).

There were no statistically significant differences in the intake of calories, carbohydrate (total and starch), fiber, protein, fat (total, saturated and trans-, mono- and polyunsaturated), sugar or alcohol in the patients with IBS who received dietary guidance (Table II). However, there was a significant increase in the intake of cholesterol. The dietary guidance did not affect the meal pattern in the patients with IBS (Table III). There was an increase in the consumption of various dairy products, although the change was not statistically significant (Table IV). However, there was a decrease in the consumption of dairy products with probiotic supplements, in line with our recommendation during the study. Although the intake of β-carotene, retinol equivalents, calcium and riboflavin was increased, only the increase in vitamin B₁₂ was statistically significant (Table V). There was a significant reduction in the consumption of various FODMAP- and insoluble fiber-rich fruits and vegetables (Table VI). The replacement of wheat and wheat products with spelt and spelt products, respectively, enabled the patients to consume the food items that they considered essential (Table VII).