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Smell strongly contributes to food choice and intake, influencing energy balance and body weight; its reduction or loss has been related to malnutrition problems. Some patients with inflammatory bowel disease (IBD), mainly Crohn's disease (CD) and ulcerative colitis (UC), are underweight, while others are overweight. Some studies suggest that changes in eating habits could be linked to specific disorders of the olfactory functions. We assessed the olfactory performance in 199 subjects (healthy control (HC) n = 99, IBD n = 100), based on the olfactory Threshold, Discrimination and Identification score (TDI score), measured with the "Sniffin' Sticks" test. Subjects were genotyped for the rs2590498 polymorphism of the OBPIIa gene. IBD patients showed both a slightly, but significantly, lower olfactory function and a higher BMI compared to HC subjects. Threshold (in both population) and Discrimination (in IBD patients) olfactory score were affected by the OBPIIa genotype. BMI was influenced by both health status and OBPIIa genotype. A lower olfactory function may delay the satiety sensation and thus increase meal duration and body weight in IBD patients. However, the AA genotype of the OBPIIa seems to "protect" IBD patients from more severe olfactory dysfunction.

The low Fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP) diet has demonstrated excellent results in terms of symptom control and health-related quality of life (HRQoL) in irritable bowel syndrome (IBS) sufferers, but patients have complained about unsatisfying taste, difficulty in following the diet, and time consumption. To investigate the feasibility of the low FODMAP diet in an Italian (Sardinian) cohort, sixty consecutive eligible outpatients (11 men and 49 women) with IBS were enrolled and followed a low FODMAP diet (gluten allowed, restriction phase of four weeks, reintroduction phase of four weeks). Food habits were assessed using 24-hour dietary recall, Bristol Stool Scale for stool consistency, Visual Analogue Scale for abdominal bloating, VAS (Visual Analogue Scale) for abdominal pain, IBS Severity Scoring System for perceived disease severity, and a 12-item Short Form Survey for HRQoL (psychological component summary + mental component summary) were applied at baseline (T0) and at the end of each phase (T1-four weeks and T2-eight weeks). Statistical analysis was performed by dividing the cohort into diarrhoea-dominant IBS (IBS-D) and other IBS subtypes (selected IBS-others). Comparisons between T1 and T2 vs. T0 and T2 vs. T1 were performed. The low FODMAP diet lowered VASp (VAS pain), VASb (VAS bloating), and IBS SSS (IBS Severity Scoring System), and increased PCS (Physical Component Summary) and MCS (Mental Component Summary) in both subgroups. Bristol Stool Scale (BSS) only improved in the IBS-D subgroup. The dropout mean values for MCS were higher than treated subjects and the percentage of unemployment was lower in the dropouts. According to the dropout features, the low FODMAP diet seems to show greater feasibility for patients with more time to dedicate to the diet (unemployed, homemakers, housewives, or students), more motivation, and more severe clinical features, independent of their place of residence.

Inflammatory bowel disease (IBD) is a chronic inflammatory condition of the gastrointestinal tract resulting from interactions among various factors with diet being one of the most significant. IBD-related dietary behaviors are not clearly related to taste dysfunctions. We analyzed body mass index (BMI) and perception of six taste qualities and assessed effects of specific taste genes in IBD patients and healthy subjects (HC). BMI in IBD patients was higher than in HC subjects. Taste sensitivity to taste qualities was reduced in IBD patients, except for sour taste, which was higher than in HC subjects. Genetic variations were related to some taste responses in HC subjects, but not in IBD patients. Frequencies of genotype AA and allele A in CD36 polymorphism ( r s 1761667 ) were significantly higher in IBD patients than in HC subjects. The taste changes observed could be explained by the oral pathologies and microbiome variations known for IBD patients and can justify their typical dietary behaviors. The lack of genetic effects on taste in IBD patients indicates that IBD might compromise taste so severely that gene effects cannot be observed. However, the high frequency of the non-tasting form of CD36 substantiates the fact that IBD-associated fat taste impairment may represent a risk factor for IBD., Competing Interests: The authors declare no conflict of interest.

Several studies have reported some efficacy of diets low in fermentable carbohydrates (Fermentable Oligo-, Di-, Monosaccharides and Polyols (FODMAPs)) in Irritable Bowel Syndrome (IBS). There is no evidence of its superiority compared to gluten-free and balanced diets in improving IBS patients' quality of life (QoL). The aim of this study is to assess whether different diets can improve QoL in IBS. Forty-two patients with IBS, according to Rome IV criteria, were enrolled. Low-FODMAP, gluten-free and balanced diets were proposed to each patient in the same succession. Each diet was followed for 4 weeks. The Bristol Stool Scale, the Visual Analogue Scale (VAS) for bloating and abdominal pain, and the SF12 questionnaire for health-related quality of life were applied at the beginning and at the end of each diet. Twenty-eight of the forty-two patients completed all the three diets. All the three diets reduced symptom severity ( p < 0.01), bloating ( p < 0.01) and abdominal pain ( p < 0.01), and improved quality of life ( p < 0.05); 3% of patients expressed a preference for the low-FODMAP diet, 11% for the gluten-free and 86% for the balanced diet ( p < 0.01). The balanced diet improves QoL and VAS pain, provides an adequate quantity of FODMAPs and is more appreciated by patients. For these reasons, the balanced diet could be recommended to patients with irritable bowel syndrome.