Benefits
Plasmacytoid dendritic cell activation (immune marker)
Pooling data from 619 healthy adults in Kirin-funded trials, daily LC-Plasma kept the pDC activation markers CD86 and HLA-DR higher than placebo. In lab work, both live and heat-killed cells have been reported to trigger interferon-alpha. These are measures of immune-cell activity, not proof of fewer or shorter colds.
Fewer days with cough and feeling feverish in healthy adults
In a meta-analysis of Kirin-funded trials (555 healthy adults), LC-Plasma reduced days with cough by about 0.7 and days feeling feverish by about 0.3 per 28 days versus placebo. Sore throat, runny nose and overall cold days did not differ significantly, and the authors rated the certainty of this evidence as low.
Interferon-alpha response in a lab comparison
In a cell-culture comparison of five heat-killed postbiotic products, only LC-Plasma was taken up by pDCs and produced measurable interferon-alpha (about 74 pg/mL); the other strains did not, even at higher doses. This is a lab result, not a level measured in people, and it does not show protection against infection.
Fatigue days in athletes during heavy training
In a Kirin-funded trial, 37 athletes took LC-Plasma capsules (100 billion cells) or placebo through 14 days of high training load. The LC-Plasma group reported fewer cumulative days of fatigue and had higher pDC CD86 expression. Most other symptoms logged in daily diaries during this summer study did not differ between groups.
Mechanism of action
Uptake by plasmacytoid dendritic cells
In lab studies, LC-Plasma is taken up by pDCs, which other tested postbiotic strains were not. An earlier Kirin study linked this kind of pDC activation by spherical lactic acid bacteria to TLR9, a receptor that senses bacterial and viral DNA.
Type I interferon signalling (proposed)
Activated pDCs release interferon-alpha, which helps put neighbouring cells into an antiviral state. This is the proposed rationale for LC-Plasma; it has not been shown to prevent infection by any specific virus in people.
Oral intake and gut immune tissue (hypothesis)
Taken by mouth, the cells reach immune tissue in the gut lining, which may explain how heat-killed bacteria that cannot colonize the gut still change blood pDC markers. This route has not been directly shown in the cited human trials.
Clinical trials
Meta-analysis of 8 randomized placebo-controlled trials, with individual data from 7, all funded by Kirin (Kato et al. 2025, Front Immunol)
Healthy adults aged 18 to 64 in Japan (7 trials) and Malaysia (1); 619 in the pDC analysis and 555 in the symptom analysis; 100 billion cells/day for 13 to 84 days.
pDC markers CD86 (SMD 0.37) and HLA-DR (SMD 0.47) stayed higher than placebo. Days with cough fell by 0.69 and with feverishness by 0.26 per 28 days. Sore throat and runny nose did not differ significantly, and overall cold days showed only a trend (p=0.061). The authors rated certainty of the symptom evidence as low.
Lab study plus a randomized, placebo-controlled, double-blind yogurt trial by Kirin researchers (Sugimura et al. 2013, Clin Immunol)
38 healthy adults drinking yogurt with live LC-Plasma (100 billion cfu/day) or placebo yogurt for 28 days in August.
LC-Plasma raised blood pDC activation markers, more so in people with low starting pDC activity, and increased their capacity to produce interferon. The authors also reported a lower risk of common cold than placebo in this small trial.
Randomized, double-blind, placebo-controlled parallel-group trial funded by Kirin (Komano et al. 2023, Nutrients)
37 athletes during 14 days of continuous high training load.
Capsules with 100 billion heat-killed cells/day raised pDC CD86 and reduced cumulative fatigue days versus placebo, and an autonomic fatigue index after a 2-hour ergometer test was lower. Other symptoms logged in daily diaries did not differ, except that days with moderate or worse joint pain were more frequent with LC-Plasma (8 vs 1).
In-vitro comparison of five commercial heat-killed postbiotic products using confocal imaging and ELISA (Fujimura et al. 2025, Microorganisms)
Cultured human pDCs; no people were given the products.
Only LC-Plasma was internalized by pDCs and induced measurable interferon-alpha (73.8 pg/mL); other strains did not, even at up to 100 billion cells. These are cell-culture markers; the study did not measure colds, infections or any clinical outcome.