Benefits
Positive mood ratings in a first 4-week trial
In 58 healthy young adults, 4 weeks of heat-killed MCC1848 improved two positive mood ratings versus placebo: friendliness on the main mood questionnaire and a feeling-relaxed rating. Friendliness was one of several scores on that questionnaire; negative mood items did not differ, and the published abstract describes no correction for testing many scores.
Positive affect scores in a second 4-week trial
In 39 analyzed nursing students, 5 billion cells a day gave higher positive affect scores than placebo averaged over weeks 2 and 4 (26.7 versus 22.1, p = 0.034), but the groups already differed before intake (25.5 versus 23.2) and neither changed significantly from baseline. Negative affect, the other main score, did not differ, and friendliness, which improved in the first trial, did not differ this time.
Negative mood and tension scores
Across both mood trials, negative mood measures did not differ from placebo: anger, nervousness, confusion and an anxiety questionnaire in the first trial, and negative affect, tension, depression-dejection and the overall mood disturbance score in the second. The trials were not designed to test anxious or low mood as a condition.
Sleep, fatigue and quality of life scores
Insomnia and fatigue questionnaire scores did not differ from placebo in either 4-week trial. In the second trial, feeling-tired and exhausted ratings and the three summary scores of a quality of life questionnaire also did not differ, so the trials offer no support for effects on sleep, tiredness or daily functioning.
Stress-related behavior in mice (lab and animal work)
In mice exposed to repeated social defeat stress, heat-killed MCC1848 increased time spent interacting with another mouse and preference for sugar water, behaviors used to model anxiety and low mood, and shifted gene activity in a brain reward region. These are animal results from the maker's laboratory and partners.
Mechanism of action
Brain reward region gene activity in mice (proposed)
In stressed mice, heat-killed MCC1848 reversed some stress-related gene expression changes in the nucleus accumbens, a brain area tied to reward and motivation. The maker's researchers propose this as the link to positive mood, but no brain or biological measure was taken in the human trials.
Inactivated cells acting through the gut (proposed)
As a postbiotic, MCC1848 delivers killed bacterial cells and their components rather than live bacteria that could grow in the gut. The authors propose effects through the gut-brain axis, but how killed cells would act on mood has not been shown, and the second trial had no objective measures.
Clinical trials
Randomized, double-blind, placebo-controlled trial of heat-killed L. helveticus MCC1848 powder for 4 weeks (5 billion cells a day according to the maker's later papers), with the shortened POMS 2 mood questionnaire as the primary outcome; sponsored by Matsumoto Junior College and funded by Morinaga Milk Industry according to the registry, UMIN000043697 (Mutoh et al. 2023, Benef Microbes)
58 healthy young adults in Japan; the registry lists enrollment in March and April 2021 with a target of 60.
Two positive mood ratings, friendliness on POMS 2 and feeling relaxed on a visual scale, improved versus placebo. Negative mood items (such as anger, nervousness and confusion), STAI anxiety, insomnia and fatigue scores did not differ. The maker's follow-up paper reports that vigor-activity showed only a trend. No adverse effects. Four of the nine authors work for Morinaga Milk Industry, which makes the ingredient.
Randomized, double-blind, placebo-controlled parallel trial at Matsumoto Junior College (March to April 2022) of one powder stick a day with 5 billion heat-killed MCC1848 cells or a maltodextrin placebo for 4 weeks, with the PANAS positive and negative affect questionnaire as the primary outcome; per-protocol analysis; registered UMIN000047065; funded by Morinaga Milk Industry (Mutoh et al. 2023, Brain Sci)
46 healthy third-year nursing students in Japan before clinical training were randomized, 43 completed and 39 were analyzed (21 MCC1848, 18 placebo; 35 women, mean age about 22). The planned 30 per group was not reached.
PANAS positive affect averaged over weeks 2 and 4 was higher than with placebo (26.7 versus 22.1, p = 0.034), but the MCC1848 group already scored higher before intake (25.5 versus 23.2, p = 0.258) and neither group changed significantly from baseline, while negative affect did not differ (p = 0.968); with two primary scores, p = 0.034 would not pass a Bonferroni cutoff of 0.025. No secondary outcome differed, including every POMS 2 scale (friendliness, which improved in the earlier trial, included), visual mood and fatigue ratings, SF-36v2, insomnia and fatigue scales. Adverse events were mild, judged unrelated and similar (21.7% with MCC1848 versus 26.1% with placebo). Five of the eleven authors are Morinaga employees.
Randomized, double-blind, placebo-controlled parallel safety trial at a Tokyo clinic (September 2024 to January 2025) of one sachet a day with 25 billion heat-killed MCC1848 cells, five times the mood-trial dose, or maltodextrin placebo for 12 weeks plus 4 weeks of follow-up; all outcomes were safety measures; registered UMIN000055233; funded by Morinaga Milk Industry (Aoki et al. 2026, BMC Nutr)
40 healthy adults aged 18 to 64 (mean age about 47) randomized 20 and 20; 39 entered the safety analysis and 37 completed.
Six adverse events in six people on MCC1848 and five in four on placebo (p = 0.480), all mild and judged unrelated, such as colds, influenza and a toe injury; no digestive complaints were reported. Some blood values changed within groups over time, for example HbA1c and LDL cholesterol rose in both groups, but all stayed within reference ranges. The trial did not measure mood. Five of the six authors are Morinaga employees.