Inclusion Criteria:  Patient giving written informed consent to participate in the study. Patient of both sexes aged between 18 and 70 years (inclusive) Patient affected by chronic functional constipation according to the Rome IV criteria In patients over the age of 50, negative colonoscopy, i.e. absence of clinically relevant alterations or in any case of critical condition for study participation, performed during the run-in period unless:  at least negative colonoscopy performed in the previous 5 years the symptoms have remained unchanged, if present, from the time of the execution of the (or last, if more than one) colonoscopy  Exclusion Criteria:  Hypersensitivity or Suspected or known allergy to one of the components of the products under study Have previously taken the study product Therapy with antibiotics within 4 weeks prior to the screening visit (i.e, prior to the visit V -1) Therapy within 2 weeks of the run-in (i.e., prior to the visit V0) with: Laxatives / fecal softeners / intestinal bulking products; Drugs indicated for the treatment of obesity; probiotics or prebiotics Chronic inflammatory bowel diseases Intestinal diseases of infectious, actinic, endocrine or pharmacologic origin (microscopic colitis) Patients undergoing gastro-intestinal resection Renal, hepatic, haematological, cardiovascular, pulmonary, neurological, psychiatric, immunological, endocrine diseases, if they are clinically significant Patients with malignant neoplasm of any type, or history of malignancy, with the exclusion of patients with a history of extra-intestinal malignant neoplasm surgically removed and no evidence of recurrence within the five years prior to participation Abuse of alcohol, narcotics or psychotropic drugs that can change vigilance and physical perception Presence of a dementia of any type or other possible causes of progressive deterioration of the capacity to understand and of want or psycho-physical disability that reduces the ability to assume as expected the study treatment Obesity (BMI ≥ 30) No adequate reliability or conditions that may lead to a non-compliance / adherence of the patient to the protocol Previous participation in a clinical trial in the last 30 days  Patients who for any reason do not agree to guarantee the commitment to keep their diet stable for the study period  During the run-in period, in case of severe symptoms, the use of an evacuant to be applied rectally, indicated in constipation and identified by the Investigator, can be used as a "rescue" therapy.