This study aims to evaluate the effects of different dietary treatments on intestinal integrity in female subjects aged 19-50 years previously diagnosed with constipation-predominant irritable bowel syndrome (IBS). At the Gülhane Training and Research Hospital's gastroenterology clinic in Ankara, Turkey, a randomized controlled experiment was carried out. 60 individuals with IBS were randomly divided into three groups. Group 1 was assigned to a regular constipation diet, group 2 to a constipation diet rich in soluble fibers, and group 3 to a constipation diet with probiotic yogurt supplementation. Every individual was monitored for eight weeks. Plasma zonulin level was used to measure intestinal integrity both before and after treatment.

This was a non-pharmacological randomized controlled trial conducted at Ankara Gülhane Training and Research Hospital Gastroenterology Polyclinic between June 2019 and March 2020. Participants of this study were women aged 19 to 50 years with a diagnosis of IBS according to the Rome IV criteria (2017).

The sample size was calculated with G*Power software. With an estimated power of 90%, a Type I error of 0.05, and an effect size of f=0.25, the total sample size required was 54, consisting of 18 participants in each group. The sample size was calculated using G*Power software. The total sample size, with an estimated strength of 90%, Type I error of 0.05, and effect size f = 0.25, was 54, consisting of 18 participants in each group. 60 participants were targeted due to compensation for potential drop-out from protocol.

Using random assignment software, participants were divided into three groups at random for parallel group randomized trials. Group 1 received a standard constipation diet; Group 2 received a soluble fiber-rich constipation diet; and Group 3 received a probiotic yogurt-supplemented constipation diet. The three groups-regular constipation diet, constipation diet high in soluble fiber, and constipation diet fortified with probiotic yogurt-were coded R 1-2, F 1-2, and P 1-2 to protect patient confidentiality. Twice a week, two liters of water, two servings of vegetables, and three servings of fruits, and legumes were the staples of the constipation diet. For the first four weeks, Group 2's constipation diet included 1 sachet of soluble fiber (resistant starch) (5 g/day), and in the second week, 2 sachets of soluble fiber (10 g/day) were added. It happens after four weeks. In Group 3, the yogurt ingested before lunch was supplemented with the IBS-specific strain "Bifidobacterium Infantis 35624 (B. Infantis 35624)". For eight weeks, there was a follow-up.

All data were collected by face-to-face survey method. At the first visit, sociodemographic characteristics and three-day food consumption were recorded. Food consumption was recorded for 3 days, 2 days on weekdays, and 1 day on weekends. Serum Zonulin level and biochemical tests were evaluated at the beginning of the diet and the 8th week. Serum Zonulin level was measured using the "BT Lab Human Zonulin ELISA Kit" (China, E1117). Daily energy and nutrient amounts taken from the diet were analyzed using the Nutrition Information System 8 (BeBis 8) computer package program.

IBM SPSS Statistics 22.00 program was used to analyze the data obtained. The normal distribution of the data was evaluated with the Shapiro-Wilk test. To increase clarity and ensure consistency with other studies, continuous variables are presented as mean ± standard deviation. Spearman rank correlation coefficients are a way to represent correlations between continuous variables. Analysis of variance or the Kruskal Wallis test was used to compare groups. Wilcoxon signed-rank test was used to compare groups within the same group from baseline to week eight. The significance threshold of p<0.05 was determined.

Inclusion Criteria:

• Women aged 19-50 years who were diagnosed with IBS according to Rome IV criteria
• Any metabolic disease (diabetes, heart disease, etc.), cancer and autoimmune no history of chronic diseases such as illness
• Not being pregnant or lactating
• Body mass index (BMI) of 18.5-29.9 kg/m2

Exclusion Criteria:

• Chronic disease history such as cancer and autoimmune diseases
• Probiotics use or nutritional supplement use (vitamins, minerals) in the last 6 months.
• Pregnancy.