The study, published in the journal Nutrients, evaluated the daily probiotic supplementation in 200 healthy adults over eight weeks, building on previous evidence of the immune health supporting properties of the Lactobacillus and Bifidobacterium strains.
“These results suggest that GCL1815 intake may enhance the response to viruses by activating two types of dendritic cells, thereby preventing the onset of systemic and local common colds in healthy adults,” wrote researchers from Ezaki Glico Co.
They noted that rather than suppressing specific symptoms, the probiotic’s beneficial effects extended from early symptoms, such as fatigue, to late symptoms, such as a runny nose, suggesting that GCL1815 effectively reduced the number of days with the common cold.
The probiotic also reduced the proportion of serious symptoms compared to placebo.
“Because more severe infections can lead to complications such as otitis media, sinusitis, bronchiolitis and pneumonia, the reduction in more severe symptoms is considered important, even for mild infections such as the common cold,” they wrote.
Immune modulation for the common cold
The common cold and influenza have a considerable economic impact in Europe, with studies estimating a cost per case ranging from €126.10 in France to €584 in Germany.
Seasonal influenza causes 3 to 5 million cases of severe illness globally each year. More than 200 different viruses are known to cause the common cold, making it challenging to tailor treatments.
Therefore, modulating immune function and supporting the body’s defenses against viral infection are helpful strategies against seasonal illness.
Dendritic cells (DCs) present antigens such as viruses and bacteria to white blood cells, triggering the adaptive immune response and stimulating the production of T-cells and B-cells.
Plasmacytoid dendritic cells (pDCs) are particularly effective at responding to viruses. The current study found that GCL1815 activated pDCs and type 1 cDCs (cDC1s), promoting T-cell production.
Previous research also suggests that probiotics such as Lactobacillus and Bifidobacterium may reduce the duration of respiratory illness and colds.
Study details
The randomized, double-blind, placebo-controlled, parallel-group study assigned 200 healthy Japanese adults between the ages of 20 and 65 into two groups that consumed capsules containing either six billion L. helveticus GCL1815 cells or placebo for eight weeks. Participants recorded any cold symptoms in a daily questionnaire.
Based on the questionnaire, the intervention group had significantly less incidence of cold symptoms such as feverishness, fatigue, tiredness, runny nose, nasal congestion and phlegm.
Blood and saliva samples showed that GCL1815 activated pDCs and cDC1s significantly more than placebo.
“It is considered that pDCs activated by GCL1815 reinforce the ability of cDC1s to uptake and present viral antigens, and that the combined action of pDCs and cDC1s promote an immune response to viral infection, thereby suppressing the onset of the common cold”, the researchers wrote.
Source: Nutrients
2025, 17(1), 101; doi: 10.3390/nu17010101
“Lactobacillus helveticus Induces Two Types of Dendritic Cell Activation and Effectively Suppresses Onset of the Common Cold: A Randomized, Double-Blind, Placebo-Controlled Trial.”
Authors: H. Wada et al.