Effects of a Probiotic Fermented Milk on Functional Constipation

A Randomized, Double-blind, Placebo-Controlled Study

Mena Mustapha Mazlyn; Lee Hun-Leong Nagarajahl Arshad Fatimah; A Karim Norimah; Khean-Lee Goh


J Gastroenterol Hepatol. 2013;28(7):1141-1147. 

In This Article


Study Design

A randomized, double-blind, placebo-controlled, parallel group study involving 100 adults with functional constipation was conducted in the Klang Valley area of Peninsular Malaysia between March and June 2010.

A third-party controller assigned color codes to probiotic and placebo drinks, respectively. Subjects were stratified based on age and severity of constipation measured using Chinese Constipation Questionnaire (CCQ)[19] score and were allocated to two groups with 1:1 ratio using randomization software. Both researchers and subjects were blinded to the allocation.

A painstaking and stringent selection process was undertaken in the recruitment of subjects. A database was obtained and broadly screened to identify a large pool of potential subjects. The database had been collected via surveys at public health awareness events organized by medical societies that were not pharmaceutical marketing events. From among the pool of potential subjects, all those who agreed to participate in the screening were interviewed by the researchers and underwent medical examination by a physician. Only those who met the strict eligibility requirements were invited to participate in the trial.

After a 2-week baseline, subjects received once-daily doses of either fermented milk with LcS or placebo nutrient drink without LcS for 4 weeks. Study drinks were delivered to subjects once every 3 days. Cold chain was maintained below 10°C during storage, transportation, and distribution. Final assessment was done 1 week postintervention. Subjects recorded information regarding their bowel movements in diaries and constipation severity was assessed weekly via CCQ[19] throughout the 7 weeks. For use in ethnic Malay subjects, the CCQ[19] was translated to Malay by expert panel forward-back translation and pre-tested. Subjects were required to maintain their usual diets and lifestyle throughout the study.

Ethical Considerations

The study was conducted in accordance with Malaysian Guidelines for Good Clinical Practice, the Declaration of Helsinki, and local laws and regulations. The protocol was approved by the joint research and ethics committee of International Medical University, Kuala Lumpur on December 17, 2009 (Research project identification no. IMU R052 2009). All subjects gave written informed consent. The study was registered at ClinicalTrials.Gov (#NCT01161784).

Safety Considerations

Adverse events (AEs) that occurred during the study were recorded. For safety assessment, only AEs that took place during intervention phase were analyzed. Stimulant laxative Dulcolax (Boehringer Ingelheim, Ridgefield, CT, USA) was assigned as rescue therapy in the event of absence of bowel movement for 4 consecutive days.

Study Agents

The test beverages consisted of fermented milk containing viable LcS ("probiotic drink") and fermented milk without LcS (placebo "nutrient drink"). The beverages were packaged in unmarked individual plastic bottles in doses of 80 mL. The ingredients were sugar, skimmed milk powder, glucose, calcium, vitamins, and permitted flavorings. Both test beverages contained approximately 1-g lactose per bottle and did not contain dietary fiber. The probiotic drink contained at least 3.0 × 1010 colony-forming unit (CFU) of live LcS per serving, while the placebo did not contain LcS. Every effort was made to ensure similarity between the probiotic and placebo drinks in terms of nutritional content, taste, color, texture, and smell, with the only difference being the presence or absence of LcS.


Subjects were of either gender aged between 18 and 60 years diagnosed with Rome II-defined functional constipation[2] with CCQ[19] score of at least 5, satisfying the CCQ[19] cut-off point for constipation. Subjects were otherwise-healthy, free of cardiovascular-related diseases, diabetes, cancer, neurological diseases, or other serious illnesses, and not physically or mentally handicapped. Subjects lived in the Klang Valley, with no predetermined plans to be out of town for longer than 6 days during the intervention. Subjects were excluded if they had a body mass index (BMI) of below 16 (severe thinness), or 30 and above (obese); were pregnant; consumed probiotic products more than once a week in the month preceding screening or at any point during intervention; regularly used laxatives (more than once a week); used anticholinergics, anti-diarrheals, or antibiotics in the month preceding screening or at any point during intervention; had milk protein allergy; had constipation of organic or neurological origin; had alarm features indicative of colorectal cancer; failed to either confirm intake of study drink or provide data records for 6 days or more during intervention; or experienced AEs that necessitated discontinuation of intervention.

Efficacy Measurements

Primary efficacy outputs: CCQ[19] severity score and stool frequency.

Secondary efficacy outputs: Stool consistency assessed on a 5-point scale modified from the Bristol stool form chart[20] and stool quantity estimations based on visual comparison of stool volume with size of 40-mm diameter standard unit (ping-pong ball).[15]

CCQ[19] score was calculated using a questionnaire consisting of six items that has been found to be satisfactory in terms of validity and reliability as a self-report measure for constipation severity by a review.[21] The six items are: (i) severity of false alarm (having urge but unable to pass stool); (ii) frequency of < 3 weekly defecations; (iii) severity of incomplete evacuation; (iv) severity of lumpy or hard stools; (v) number of laxatives used; and (vi) severity of abdominal bloating.[19] Items (i), (ii), (iii), (iv), and (vi) are rated using a 5-point Likert scale.

Sample Size

Sample size was determined based on primary end-point measures, CCQ[19] score, and stool frequency. According to priori power analysis for two-tailed t-test,[22] with α error 0.05 and β error 0.20, assuming mean change in CCQ score and weekly stool frequency of −3.5 and +0.95, and standard deviation of 5.0 and 1.5, respectively, a total of 80 subjects (40 per group) were needed. However, if α level was set at 0.10, while other parameters remained unchanged, the minimum sample size required would be 26 (13 subjects per group).

Statistical Analysis Plan

Analysis was conducted on intent-to-treat population (i.e. all randomized subjects exposed to at least one dose of study drink, with at least one post-baseline efficacy assessment, and excluding outliers with major eligibility violation—possible misdiagnosis). Student's t-test or non-parametric equivalent (α = 0.05 level) was employed to compare the mean primary efficacy outcomes of the probiotics and control at weekly intervals. Baseline values are the mean of 2-week pre-intervention period. Magnitude of change was computed using Cohen's effect size.