The purpose of this study was to evaluate the efficacy of 1 capsules of ABKefir per day on symptoms of constipation in subjects with functional constipation by clinical trial.

This randomized, placebo-controlled clinical trial will be conduct for 8 weeks with one hundred and sixty-five adults. Subjects will be recruited and randomly assigned into three groups: (1) placebo, n = 55; (2) low dose of ABKefir , n = 55; (3) high dose of ABKefir, n = 55. During the first 4 weeks of supplement, the subjects should take one capsule of placebo or ABKefir daily. Apart from containing no probiotics, the content of placebo is same as ABKefir. After that, the next 4 weeks is to have a follow-up of subjects. During this phase, subjects don't need to supplement. Subjects should complete the assessment of anthropometric measurement, defecation questionnaire , food record, feces and blood collection at week 0, 4 and week 8.

Inclusion Criteria:

• male or female
• aged 18-75 years old
• fulfill Rome IV criteria for functional constipation
• have not participated in similar research in the past three months

Exclusion Criteria:

• Personal or family history of colon cancer, celiac disease, and inflammatory bowel disease
• Irritable bowel syndrome diagnosed during colonoscopy
• Those who are pregnant recently (including men and women), or are pregnant or breastfeeding women.
• Taking antidepressants, anti-anxiety drugs and other psychotropic drugs.
• Long-term medication is required to improve constipation
• Those diagnosed with myocardial infarction, cerebral infarction, malignant tumor and/or other serious diseases are not suitable for participating in the study.
• Allergic symptoms to probiotics or any ingredients
• Having a history of serious mental illness
• Drug-related crimes or alcohol problems
• Have recently traveled to areas where parasitic diseases are prevalent.