Once the patients who are candidates to enter the study are identified, the patients will be randomly be assigned to two groups, according to the sequence:

• Group A: study product+wash out+control product
• Group B: control product+wash out+study product

All patients will be given guidelines for adopting dietary habits and healthy lifestyles to achieve a regular and physiological depositional rhythm and will be given a study supplement and a control supplement, alternatively, for 2 time periods of 3 weeks separated by 2 weeks of wash out.

• Supplement under study: mixture of food fibers of plant origin, in a proportion that contributes 75% soluble fiber / 25% insoluble fiber.
• Control: Placebo supplement: maltodextrin and plum flakes

Inclusion Criteria:

• Boys and girls aged 3 to 12
• Diagnosis of functional constipation according to Rome IV criteria

Exclusion Criteria:

• Regular use of a dietary fiber supplement, prebiotics or probiotics in the previous 30 days, or who would have been taking bulk-forming agents or laxatives in the 2 weeks prior to the study
• Use of medications that cause constipation
• Children with organic constipation such as Hirschsprung's disease, cerebral paralysis, anorectal and spinal cord abnormalities and metabolic diseases.
• Patients who are not likely to complete follow-up