I know of only three probiotics that have been proven through clinical trials to be effective for IBS: VSL#3, lactobacillus plantarum and Bifidobacterium infantis 35624 (Align). A recent review of probiotics in clinical practice (see first reference below) indicates that only certain species of lactobacillus and bifidobacterium have any efficacy for IBS.
VSL#3 and lactobacillus plantarum were small trials showing limited efficacy compared to placebo. There have been three Bifidobacterium infantis 35624 trial that were much larger and the efficacy was high for all IBS symptoms in IBS-C and IBS-D. The mechanism by which the later probiotic works in IBD to reduce localized bowel inflammation is better understood (see second reference below) and hypothesized to be similar in IBS. VSL#3 contains a variety of organisms including lactobacillus plantarum and Bifidobacterium infantis (perhaps different strain than 35624) and this may be part of the reason for its partial efficacy in IBS.
It is not the number of organisms in a probiotic that determines it's effectiveness. It is the type, species and amount of individual organisms that determine the efficacy. While there may be other probiotics that are effective for IBS they have not been clinically proven. I won't rely on self-reports from one or even few individuals to judge the efficacy of any probiotic on IBS.
I hope this helps
Reference Zuccotti, G. V., et. al., 2008: Probiotics in clinical practice: An overview. Journal of International Medical Research, 36, 1A-53A.
Shiba, T., et. al., 2003: The Suppressive Effect of Bifidobacteria on Bacteroides vulgatus, a Putative Pathogenic Microbe in Inflammatory Bowel Disease. Microbiology and Immunology, 47, 371-378
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