Lactobacillus rhamnosus GG is the most studied and well-characterized probiotic strain, it was patented 30 years ago. It produces lactic acid, it ferments rhamnose. It is able to survive to gastric acidity and bile salts, to adhere to the intestinal mucosa, it modulates the immune system and epithelial cells apoptosis.
Among the beneficial properties of LGG on human health, there is its antidiarrheal activity, exerted as prevention in diarrhea development and/or reduction of its duration, also in children. Let’s analyse the clinical studies supporting this activity.
The clinical study from Vanderhoof and colleagues (1999) recruited 188 children who were administered an antibiotic therapy, simultaneously treated with placebo or LGG (2 × 1010 CFU/day). Results show that LGG treatment significantly reduces the incidence of antibiotic-associated diarrhea, as highlighted from the following graph. Gere we can observe that evacuation frequency significantly increases during the antibiotic therapy, meanwhile remains constant in those assuming LGG.

The study states that in parallel to the increase of evacuation frequency, it was observed a progressive modification of stool consistency in patients not treated with LGG, becoming more and more soft.
Another example of LGG antidiarrheal activity was reported by Basu and colleagues (2007). They recruited 235 patients with persistent diarrhea, receiving oral rehydration solution (ORS) or oral rehydration solution added with LGG (6*107 CFU twice/day) (ORS+LGG). The results show that starting from the fourth day of treatment, the diarrhea is significantly less frequent in the LGG group and that, at ninth day of treatment, they actually don’t experience diarrhea anymore. The mean duration on diarrea, in fact, is 5 days in the LGG group, compared to nine in those receiving only ORS.

In conclusion, LDD significantly decreases the frequency of diarrheal episodes starting from the fourth day of consumption and significantly decreases diarrhea duration.
These studies demonstrate the efficacy of LFF in controlling the most frequent symptom experienced in gut conditions of different cause and nature.
References
Basu, S., Chatterjee, M., Ganguly, S., & Chandra, P. K. (2007). Effect of Lactobacillus rhamnosus GG in persistent diarrhea in Indian children: a randomized controlled trial. Journal of clinical gastroenterology, 41(8), 756-760.
Vanderhoof, J. A., Whitney, D. B., Antonson, D. L., Hanner, T. L., Lupo, J. V., & Young, R. J. (1999). Lactobacillus GG in the prevention of antibiotic-associated diarrhea in children. The Journal of pediatrics, 135(5), 564-568.