Fructosin® is a medical device for use in fructose intolerance. In this uncontrolled posdt market clinical follow up (PMCF) study, the safety and efficacy of oral supplementation of Fructosin® in fructose intolerance will be investigated.

The study participants will be informed about the nature and scope of the study during a preliminary examination (screening) and a declaration of consent will be obtained. In addition, it is determined whether fructose intolerance is present. This is determined by means of the aCPQ test. Subsequently, the patients fill out symptom questionnaires (IBS-SSS, IBS-QoL, 1-week symptom questionnaire).

After the eligibility check, a 14-day phase of monitoring and documentation of symptoms and complaints without taking Fructosin® (observation phase) takes place. At visit 1, the patients receive the Fructosin® capsules, which they take as needed, but no more than 2 x 3 times a day with fruit meals. The intake phase runs over a period of 28 days (4 weeks) during which the study participants observe and evaluate gastrointestinal symptoms with the help of the 1-weekly symptom questionnaire. In addition, the daily fructose consumption (fruit, fruit juices, smoothies) and the amount of Fructosin® capsules taken are documented in a diary.

Inclusion Criteria:

• Positive result of the aCPQ test after 25 g fructose ingestion.
• Age: 18 - 80 years; 18 years of age must be completed and the legal capacity must be given.

Exclusion Criteria:

• Pregnancy and breastfeeding
• Congenital (hereditary) fructose intolerance
• Participation in a clinical trial in the past 4 weeks
• At the investigator's discretion: physical findings or previous illness for which a recommendation to take fructosin is not indicated or for which an assessment of the questionnaire by the patient is not possible.

Test persons are recruited from the patient pool of the Clinical Department of Gastroenterology and Hepatology of the Medical University Clinic Graz. Fructose intolerance has been detected in these patients by means of aCPQ since March 2017. In addition, those affected will be approached through advertising measures and an aCPQ test for fructose intolerance determination will be carried out as part of the study. A detailed medical history will also be taken to check eligibility for participation in the study.