Probiotics containing Bifidobacterium appear to be the most effective in treating constipation, according to Harvard Health Publications. However, there is currently insufficient evidence to recommend a specific probiotic for constipation, states Dr. Alan Walker, a Harvard Medical School Director and probiotics expert.
Researchers at London's King College pooled results from 14 clinical trial studies and concluded that probiotics increase the number of weekly bowel movements by 1.3 and aid stool softening, which facilitates easier bowel movements, notes Harvard Health Publications. Pooled results of different studies with differing designs is not as conclusive as a large, standardized study. In the meantime, self-experimentation with probiotics is generally harmless, as they do not seem to have any adverse side effects.