Non-celiac gluten sensitivity (NCGS) or 'wheat sensitivity' (NCWS) is included in the spectrum of gluten-related disorders. No data are available on the prevalence of low bone mass density (BMD) in NCWS. Our study aims to evaluate the prevalence of low BMD in NCWS patients and search for correlations with other clinical characteristics.

This prospective observation study will include 90 NCWS patients with irritable bowel syndrome (IBS)-like symptoms, 90 IBS and 90 celiac controls. Patients will be recruited at the Internal Medicine and at the Gastroenterology Units of the University of Palermo. Elimination diet and double-blind placebo controlled (DBPC) wheat challenge proved the NCWS diagnosis. All subjects underwent BMD assessment by Dual Energy X-Ray Absorptiometry (DXA), duodenal histology, Human Leukocyte Antigen (HLA) DQ typing, body mass index (BMI) evaluation and assessment for daily calcium intake.

Celiac disease (CD) has been reported to increase the risk of osteoporosis, with a resulting augmented risk of fractures. More recently, it has been reported that a consistent percentage of the general population consider themselves to be suffering from problems caused by wheat and/or gluten ingestion, even though they do not have CD or wheat allergy. This clinical condition has been named Non-Celiac Gluten Sensitivity' (NCGS). In a previous paper the investigators suggested the term 'Non-Celiac Wheat Sensitivity' (NCWS), since it is not known what component of wheat causes the symptoms in NCGS patients, and the investigators also showed that these patients had a high frequency of coexistent multiple food hypersensitivity. That previous study also showed a percentage of NCWS patients had weight loss and anemia: whether these depended on the intestinal malabsorption or not remains unclear. As yet no data are available on the presence and prevalence of low bone mass density (BMD) in NCWS patients. The aims of the present study is: 1) to investigate the prevalence of low BMD in NCWS patient and 2) to search for a possible correlation between BMD and other clinical characteristics, in particular the body mass index (BMI), of NCWS patients.

Inclusion Criteria:

To diagnose NCWS the recently proposed criteria will be adopted. All the patients will meet the following criteria:

• negative serum anti-transglutaminase (anti-tTG) and anti-endomysium (EmA) immunoglobulin (Ig)A and IgG antibodies;
• absence of intestinal villous atrophy;
• negative IgE-mediated immune-allergy tests to wheat (skin prick tests and/or serum specific IgE detection);
• resolution of the IBS symptoms on standard elimination diet, excluding wheat, cow's milk, egg, tomato, chocolate, and other self-reported food(s) causing symptoms;
• symptom reappearance on double-blind placebo-controlled (DBPC) wheat challenge. As the investigators previously described in other studies, DBPC cow's milk protein challenge and other "open" food challenges will be performed too.

Additional inclusion criteria will be:

• age >18 years; follow-up duration longer than six months after the initial diagnosis;
• at least two outpatient visits during the follow-up period.

Exclusion Criteria:

• positive EmA in the culture medium of the duodenal biopsies, also in the case of normal villi/crypts ratio in the duodenal mucosa;
• self-exclusion of wheat from the diet and refusal to reintroduce it, before entering the study;
• other "organic" gastrointestinal disorders;
• nervous system disease and/or major psychiatric disorder;
• physical impairment limiting physical activity;
• menopause;
• steroid and sex steroid therapy, hormone replacement therapy or ovariectomy.

The study will include consecutive adult patients with irritable bowel syndrome (IBS)-like clinical presentation, according to Rome II criteria, and a definitive diagnosis of NCWS, referred at the Internal Medicine and at the Gastroenterology Units of the University Hospital of Palermo, between may 2015 and may 2017.