The researchers investigated the effect of LGG on stress and bowel movements in young adults, most of whom were university students and who, as a demographic, are likely to experience high, persistent stress due to academic, social and financial pressures.
“Probiotics may serve as a potential adjunctive strategy for stress management in males, pending confirmation in larger and longer placebo-controlled trials,” wrote the researchers in Saudi Arabia.
Gut–brain axis links probiotics to stress reduction
Globally, studies show that approximately 35% of individuals across 131 countries experience stress, with higher rates among females.
The gut microbiota is recognized as a key regulator of brain function and behavior through the gut–brain axis, which integrates neural, hormonal and immune pathways. Gut microbes influence emotional regulation, cognition and vulnerability to neuropsychiatric conditions.
Studies suggest that probiotics may help prevent or manage conditions such as diabetes, cardiovascular disease, infections, cancer, depression and stress-related disorders.
The researchers on the new study noted that by modulating the gut–brain axis, probiotics offer a promising, low-cost approach to managing stress.
Probiotic supplementation linked to lower stress levels
The researchers recruited 66 healthy Saudi men and women aged 18 or older who reported moderate to high perceived stress to participate in the randomized controlled trial, where they were randomly assigned them either to a control group or to a probiotic group.
Researchers collected baseline data, including demographics, perceived stress scores, anthropometric measurements and bowel function. In a follow-up visit, researchers reassessed stress and bowel function through questionnaires.
The probiotic group consumed one daily capsule of Lactobacillus rhamnosus GG for 30 days, while the control group received no treatment. The probiotic was Dicoflor 60, a supplement manufactured by S.I.I.T. srl, based in Milan, Italy. Participants consumed the capsules with food and recorded adherence in a tracking diary.
After 30 days, both the probiotic and control groups showed significant within-group reductions in stress from baseline to post-intervention. Notwithstanding, the probiotic group reported significantly lower stress scores than the control group. No changes in bowel movements were observed.
Results also showed that the probiotic supplementation significantly reduced stress in the total sample and in males, but not in females.
The researchers noted that the sex-specific response was consistent with emerging evidence of differential probiotic effects in males and females that points to biological mechanisms such as microbiome composition, interactions with sex hormones, immune and hypothalamic–pituitary–adrenal axis regulation and microbial metabolites.
“Our findings suggest this probiotic can be considered as an adjunct for reducing stress in those with moderate to high baseline stress, while expectations for short-term changes in bowel habits should remain modest,” the researchers wrote.
They added that the results underscored the “relevance of the gut-brain axis in stress modulation,” noting that further research is required into strain-specific efficacy and mechanistic pathways.
Source: Frontiers in Nutrition. doi: 10.3389/fnut.2025.1717047. “The effect of probiotic supplementation on perceived stress and bowel function in healthy young adults: evidence from a randomized controlled trial in Makkah”. Authors: Noorwali, E. et al.
