Lactobacillus rhamnosus is a species of bacteria that occurs in dairy products and the human digestive tract. The genus Lactobacillus refers to the bacteria’s ability to convert sugars to lactic acid. Lactobacillus rhamnosuswas once considered a subspecies of L. casei but was subsequently determined to be a species of its own. Like all probiotic bacteria, it has been the subject of recent interest in regard to health benefits that extend beyond the digestive tract.
As of 2013, the genomes of 100 strains of L. rhamnosus have been mapped, including the well-studied GG strain, named after Sherwood Gorbach and Barry Goldin, who first filed a patent for this strain in 1985.
When consumed as a dairy product or as a lyophilized powder, LGG [ Lactobacillus rhamnosus GG] colonizes the gastrointestinal tract for 1-3 days in most individuals and up to 7 days in about 30% of subjects,” Sherwood Gorbach writes. “Traveler's diarrhea, antibiotic-associated diarrhea, and relapsing Clostridium difficile colitis are improved with LGG. In infantile diarrhea, the severity and duration of the attack is reduced. . . . LGG has proven beneficial effects on intestinal immunity. 
L. rhamnosus has been considered to be transient and noncolonizing, a study involving human volunteers who received a whey drink fermented with
L. rhamnosus GGfound that the strain attached to colonic mucosa and remained for more than a week after discontinuation of consumption. A study that involved five human colonoscopy patients who received biopsies in various colon locations after consuming whey fermented with
L. rhamnosus GGrevealed that the bacterium was present in four of the participants in their biopsy samples, suggesting that it is able to adhere to the colon.
A comparison of five lactobacilli found that L. rhamnosus GR-1was the most effective at displacing the fungus Candida albicans, which is a common source of vaginal and oral infections. In a model of oral candidiasis, L. rhamnosus GG metabolically reprogrammed C. albicans so that it failed to damage tissue, in addition to affecting the fungus’s virulence, including its ability to invade tissues.
A follow-up study of four randomized trials that included a total of 303 mother-infant pairs found a lower risk of allergic disease in comparison with a placebo among children who received perinatal probiotics. Among the 133 children who received
L. rhamnosus GG, the risk was 38% lower than those who received a placebo.
In a trial involving 202 children, Lactobacillus rhamnosus GGsupplementation lowered the incidence of diarrhea, a common side effect of antibiotics. A similar trial that included 119 children who were prescribed oral antibiotics for acute respiratory infections resulted in a 5% incidence of diarrhea within 2 weeks of antibiotic treatment among those who received Lactobacillus rhamnosus GG, while among those who received a placebo, the incidence was 16%. A systematic review and meta-analysis of randomized controlled trials that compared the effects of the administration of L. rhamnosus GGto a placebo or no additional treatment found that the probiotic lowered the risk of developing antibiotic-associated diarrhea by approximately one-half. The benefit appeared to be greater among children.
Another meta-analysis, which included randomized trials that evaluated the effect of L. rhamnosus GGin children with abdominal pain-related functional gastrointestinal disorders, found a 31% higher rate of treatment response, defined as no pain or less pain intensity, among those who received the probiotic compared to subjects who received a placebo.The rate of response was even greater among a subgroup with irritable bowel syndrome, who also experienced a reduction in pain frequency.
Intensive-care-unit stays can put patients at risk of contracting gastric and respiratory tract infections, including those associated with the bacterium Pseudomonas aeruginosa.In a randomized, double-blind, placebo-controlled pilot study, 208 patients with a unit stay of at least 48 hours were given Lactobacillus rhamnosus or a placebo twice per day from the third day following admission until their discharge. Those who received the probiotic experienced a delay in time to P. aeruginosa respiratory colonization and/or infection in comparison with the placebo group.
A recent randomized pilot study of men and women with adult acne found increased odds of improvement among those who received a liquid supplement that contained L. rhamnosusSP1 compared to participants who received a placebo. “Because both the gut-skin axis and dysregulation of insulin signaling have been implicated in the pathogenesis of adult acne, we designed the current study to evaluate the effect of supplementation with the probiotic strain Lactobacillus rhamnosus SP1 (LSP1) on skin expression of genes involved in insulin signaling and acne improvement in adult subjects,” explain G. Fabbrocini and colleagues. “We conclude that supplementation with the probiotic strain LSP1 normalizes skin expression of genes involved in insulin signaling and improves the appearance of adult acne.”
According to a report published in the Journal of Clinical Gastroenterology, some of the benefits of probiotics may be attributable to secreted probiotic-derived factors called “postbiotic” mediators. In human colonic smooth muscle cell cultures exposed to a proinflammatory compound, postbiotic mediators secreted by L. rhamnosus GGhelped protect the cells against damage, leading the authors to conclude that L. rhamnosus GG -derived products could reduce the risk of progression to postinfective motor disorders.
Could L. rhamnosus have a life-extending effect? In the oft-studied roundworm C. elegans, Lactobacillus rhamnosus CNCM I-3690 increased viability by 30% following exposure to a compound that induces oxidative stress in comparison with worms given control bacteria, while other lactobacilli failed to confer significant resistance. L. rhamnosus CNCM I-3690 also increased average lifespan of C. elegans by 20% compared to controls. Further research revealed that the probiotic had an anti-inflammatory effect. “Altogether, these results show that, among the 78 lactic acid bacteria strains analyzed; only Lactobacillus rhamnosus CNCM I-3690 strain induced a strong resistance to oxidative stress in C. elegans,” authors Gianfranco Grompone and colleagues conclude. “These results correlate the antioxidant effects of L. rhamnosus CNCM I-3690 in C. elegans with the strong anti-inflammatory profile of this strain when co-cultured with human epithelial and/or Dendritic Cells and, likewise, its ability to reduce inflammation in a murine model of colitis.”
An analysis of 6 randomized studies that included a total of 1,909 young and elderly subjects who received L. rhamnosus GG alone or in combination with other probiotics, including L. rhamnosus Lc705, found no significant differences in adverse effects between participants who received the probiotics and those who received a placebo.16 Other research documented long-term safety and normal growth and development among children who received formulas containing L. rhamnosus GG through 5 years of age.
Individuals with compromised immune systems or ulcerative colitis should ask their physicians about using L. rhamnosus and other probiotic formulas.
Lactobacillus rhamnosus is one of several probiotics species that is increasingly being recognized for its role in human health. The unique benefits revealed so far in association with this probiotic call for deeper investigation into its effects in human health.
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