How can probiotic improve irritable bowel syndrome symptoms?

Table 3 Outcomes of randomized controlled trials of probiotics versus placebo in the C and D type of irritable bowel syndrome

Ref.	Type of IBS	Sample size	Probiotic	Outcome by the type of IBS (probiotic group)
Agrawal et al[102], 2009	C	34	Bifidobacterium lactis DN-173 010	Reduction in bloating and distension (-1.52 cm), reduction of orocaecal (-1.2 h) and colonic (-12.2 h) transit times, reduction of pain and discomfort (-0.5)
Michail et al[105], 2011	D	24	VSL#3: Lactobacillus acidophilus, L. plantarum, L. casei, and L. delbrueckii ssp. bulgaricus, Bifidobacterium breve, B. longum, and B. infantis and Streptococcus salivarius ssp. thermophilus	Significant decreases in the bloating, diarrhea, satiety and QOL in both groups (placebo and probiotic)
Ki Cha et al[106], 2012	D	50	Lactobacillus acidophilus, L. plantarum, L. rhamnosus, Bifidobacterium breve, B. lactis, B. longum and Streptococcus thermophilus	Symptoms (abdominal pain, abdominal discomfort, loose/watery stool, urgency, mucus in stool, bloating, and passage of gas) relief was higher (> 50%), improved stool consistency
Abbas et al[50], 2014	D	72	Saccharomyces boulardii	Decrease in the blood and tissue levels of proinflammatory cytokines IL-8 and TNF-a and and increase in the anti-inflammatory IL-10, improvement in body image and food avoidance
Lorenzo-Zúñiga et al[93], 2014	D	84	Lactobacillus plantarum (CECT7484 and CECT7485), Pediococcus acidilactici (CECT7483)	Improved QOL score, improvement in gut-related anxiety (VSI scale)
Majeed et al[107], 2016	D	36	Bacillus coagulans MTCC 5856	Decrase in bloating, diarhea, vomiting, abdominal pain, improvement in Bristol stool score
Mezzasalma et al[108],2019	C	150	Lactobacillus acidophilus, L. reuteri, L.s plantarum, L.s rhamnosus, Bifidobacterium animalis subps. lactis	QOL improved in probiotic group, incresead healthier characteristic in stool samples
Hod et al[109],2017	D	107	Lactobacillus rhamnosus LR5, L. casei LC5, L. paracasei LPC5, L. plantarum LP3, L. acidophilus LA1, Bifidobacterium bifidum, BF3, B. longum BG7, B. breve BR3, B. infantis BT1, Streptococcus thermophilus ST3, L. bulgaricus LG1, Lactococcus lactis	No difference between groups overall, no CRP and fecal calprotectin levels difference
Ishaque et al[110],2018	D	360	Bio-Kult®	Reduced overal IBS-SSS score by 145 point in 30 d, reduced number of bowel movements, symptom free patients (33.7% vs 12.8%)
Khodadoostan et al[111],2018	D	67	Lactobacillus casei, L. acidophilus, L. rhamnosus, L. bulgaricus, Bifidobacterium breve, B. longum, and Streptococcus thermophilus with prebiotic of ructooligosaccharides	Improvement in stool consistency adn defecation rate after 3 mo, decrease in abdominal pain after 6 mo
Sun et al[112], 2018	D	200	Clostridium butyricum	Reduction in IBS-SSS score (-62.12 vs -40.74), no difference in abdominal pain and bloating, improvement in QOL, no change in Bristol stool scale.

IBS: Irritable bowel syndrome; IBS-SSS: Irritable Bowel Syndrome Severity Scoring System; D: Diarrhea irritable bowel syndrome; C: Constipation irritable bowel syndrome; QOL: Quality of life.