Polydextrose (PDX) (8-30g/day) has been reported to increase faecal bulk and consistency, leading to easier stool passage in healthy subjects. Studies on its effect on defaecation frequency and colonic transit time have provided mixed results. The primary objective was to investigate the effect of PDX consumption by mildly constipated subjects on faecal bulk, measured as total faecal wet weight of 4-day collections. Secondary outcomes (faecal dry weight, defaecation frequency, stool consistency, ease of stool passage, total colonic transit time and gastrointestinal symptoms) were also explored. 51 subjects participated in a 4-week, two-center, randomized, double-blind, placebo-controlled, parallel study testing a control (CON) and a PDX treatment (18 g/d included in biscuits and drink mixtures)

Inclusion Criteria:

1. Mildly constipated healthy adults (who defecate 3- 5 days per week assessed by a 7-day bowel diary)
2. Provision of signed and dated informed consent prior to any study procedures
3. Body mass index (BMI) ≥ 19 and ≤ 29 kg/m2 at the screening visit
4. Total score on fibre intake questionnaire max 17 points for women and 20 points for men (where each point represents approximately 1 g fibre intake)
5. Use of adequate contraception in females of childbearing potential

Exclusion Criteria:

1. Regular use of laxatives
2. Use of medication which alters study subjects' gastrointestinal function (e.g. including but not exclusive neuroleptic medication, medication for Parkinson disease, opioids)
3. History of digestive disease (e.g. celiac disease, Crohn's disease, ulcerative colitis, gastrointestinal malignancy, fistula of intestine, ischemic colitis, bile acid malabsorption, repeated diverticulitis)
4. Type I and II diabetes
5. Previous major gastrointestinal surgery (e.g. intestinal resection, total gastrectomy, subtotal gastrectomy) or surgical treatment of obesity (within 6 months before the screening visit)
6. Present cancer (except basal cell skin cancer or squamous cell skin cancer, carcinoma in situ)
7. Untreated thyroid disease
8. History of stroke or myocardial infarction within six months prior the screening visit
9. Subjects who were actively dieting for weight loss, or had eating disorders (anorexia, bulimia)
10. Lack of compliance to the study procedures
11. Females who were pregnant or breast-feeding or planning pregnancy
12. Known or suspected abuse of alcohol (more than 14 units of alcohol per week, one unit = 4 cl spirit, 12 cl wine or 33 cl medium strong beer / cider),
13. Allergy/hypersensitivity/intolerance to study products
14. Vegetarians or regularly consuming fibre supplements/fibre supplemented foods
15. Any clinically significant disease/condition which in the Investigator's opinion could interfere with the results of the study