Just one week of supplementation with the heat-killed strain was associated with relief from abdominal pain and rumbling stomach, and alterations in gut microbiota composition for students.
Researchers from Tokyo University of Agriculture and Technology reported that the supplement appears to alter specific metabolic pathways and metabolite levels, leading to symptom improvement.
The gut-brain axis
Previous research has shown that stress is strongly associated with gastrointestinal discomfort, and the gut microbiota is thought to play a significant role in this context.
Numerous studies have looked at whether probiotics could relieve stress by boosting beneficial bacteria, but few have looked at the specific effects of EC-12.
Enterococcus faecalis strain EC-12 is a lactic acid bacterium that reportedly has several health benefits, including its ability to activate cytokines and modulate the immune response.
The researchers therefore set out to investigate the impact of oral supplementation with heat-killed EC-12 on gastrointestinal discomfort caused by stress in 27 healthy university students.
Assessing physical and mental symptoms
The participants (aged 20-24) were randomized into two groups—EC-12 (n = 14) or placebo (n = 13)— and instructed to consume one pack of the EC-12 supplement or placebo daily for one week during examinations.
The students also completed the 100 mm visual analogue scale (VAS) before and after the trial and provided fecal and saliva samples.
The VAS was used to assess physical symptoms (abdominal pain, stomach rumbling and diarrhea) and mental experiences (stress, nervousness and anxiety).
Stress appeared to manifest as gastrointestinal discomfort
More than 90% of the participants taking EC-12 reported an improvement in abdominal pain and rumbling stomach symptoms, which was a significantly higher percentage than that in the placebo group. No differences in diarrhea symptoms were observed between the two groups.
In the EC-12 group, participants reported improvements in stress, nervousness and anxiety, but these improvements were not significantly different from those reported in the placebo group. There were also no significant differences between the two groups’ salivary cortisol concentrations.
“These results suggest that the stress experienced by students may not significantly impact mental health to precipitate severe symptoms but may, instead, primarily manifest as gastrointestinal discomfort,” the researchers explained.
Effect of EC-12 supplementation on the gut microbiota
While the composition and diversity of the gut microbiota did not change significantly after supplementation with EC-12, the relative abundance of E. faecalis significantly increased.
“Substantial research has suggested that products containing dead beneficial bacterial cells and their metabolites can elicit biological responses similar to those of live cells,” the researchers wrote.
The EC-12 group also had elevated levels of tryptamine in their feces after the trial. The ratio of students with improved digestive symptoms, particularly rumbling stomach, was higher among those with increased tryptamine levels.
The supplement also altered specific metabolic pathways related to alanine, aspartate, glutamate and galactose metabolism, which play crucial regulatory roles in metabolism, immunity and inflammation.
“These results suggest that oral supplementation with EC-12 has a potentially beneficial effect on stress-induced gastrointestinal discomfort, which may occur through alterations in gut microbiota composition and metabolism,” the researchers concluded.
However, due to the limited sample size and lack of in-depth investigations into the specific mechanisms of action of EC-12, they encourage further research to validate the findings.
Source: Beneficial Microbes
2024: doi: 10.1163/18762891-bja00046
“Oral supplementation of heat-killed Enterococcus faecalis strain EC-12 relieves gastrointestinal discomfort and alters the gut microecology in academically stressed students.”
Authors: J. Li, et al.