Probiotic B. longum BB536 may prevent common cold symptoms, but more research needed to understand how it works

Researchers evaluated the effect of Bifidobacterium longum​ BB536 (B. longum​ BB536) on healthy adults in a double-blind, randomised, placebo-controlled trial. They found that B. longum​ BB536 may be able to reduce the occurrence of common cold-like symptoms.

“Although not significantly different, the number of days with symptoms, occurrences, and incidence rates of many symptoms, such as chills, general malaise, and articular pain, were lower in the BB536 group than in the placebo group during the test period,” wrote the researchers in Journal of Functional Foods.​

Common cold conditions are common illnesses that affect a wide range of people. In recent years, COVID-19 has had a considerable impact on global health. Previous studies suggested that B. longum​ BB536 protects against viral infection by regulating the immune system. However, these studies were focused on elderly or young individuals.

Therefore, to study the immune effects of B. longum​ BB536 on cold-like symptoms in healthy adults, researchers conducted a randomised, placebo-controlled, double-blind study.

Between September 2021 and October 2021, researchers from Morinaga and Matsumoto City Hospital recruited participants who tended to catch a cold in Matsumoto City, Japan.

By February 2022, 200 participants aged between 20 and 60 years were equally divided into two groups: the BB536 group and the placebo group. All participants were classified according to the frequency of experiencing a common cold during the past three years: none or once, twice, and three times or more.

The BB536 group were each given a packet of powder that contained 1 × 1010 colony forming units (CFU) of B. longum BB536​. The placebo group received a similarly packaged powder that contained dextrin. Both powders were indistinguishable in taste and appearance.

One packet of the test food or placebo food was taken daily with 100 mL of the milk for 12 weeks, with a two week pre-observation period and a one week post-observation period.

During the test period, all participants were instructed to refrain from consuming healthy foods and supplements that could affect their daily health conditions and healthy foods and supplements containing bifidobacteria and lactic acid bacteria. All the contents were recorded in an electronic diary in this study.

All subjects used this survey diary to record nine cold-related symptoms during the study period: (1) feverishness, (2) chills, (3) general malaise, (4) sneezing or running nose, (5) nasal congestion, (6) sore throat, (7) cough, (8) articular pain, and (9) muscle pain.

The researchers classified the above into systemic symptoms (those that affect the entire body) and local symptoms (those that affect a specific location on the body). They found it noteworthy that feverishness could be suppressed across the age groups.

“Daily consumption of B. longum​ BB536 for 12 weeks significantly suppressed the incidence of feverishness. Significant reductions of 60% or more in the number of days with feverishness, the number of occurrences of feverishness, and the incidence rate of feverishness were demonstrated in the BB536 group compared to the placebo group,” said the researchers.

“In addition, the group that consumed B. longum ​BB536 had lower values regardless of the incidence of the common cold during the past three years.”

Feverishness is one of the systemic symptoms in common colds, so researchers speculated that B. longum​ BB536 may have protected the host participants against viral infection and suppressed viral proliferation.

These results suggest that daily supplementation with B. longum ​BB536 may suppress the risk of common cold-like symptoms, including systemic and local symptoms, in healthy adults.

“Combined with these results in preschool children and elderly individuals, B. longum ​BB536 is expected to be effective at suppressing common cold-like symptoms, including feverishness, in a wide range of age groups, thereby contributing to the maintenance of physical health,” wrote the researchers.

“These results suggest that B. longum​ BB536 may be a safe and promising probiotic for reducing the occurrence of subjective symptoms of physical conditions associated with common cold-like symptoms,” concluded the researchers.

However, the researchers acknowledged that this study has limitations. First, it remains unclear what factors and mechanisms are associated with the suppression of common cold-like symptoms mediated by B. longum​ BB536 due to the lack of objective indicators for stool, blood, and saliva samples from subjects.

Second, due to the prevalence of COVID-19 in Japan during the study period, the lifestyle of the participants was severely restricted. Thus, the onset of cold symptoms or fever could be suppressed in such an environment. Finally, this study included many assessment items for subjective symptoms and did not account for multiplicity.

“Future studies are needed to elucidate the detailed mechanisms by which B. longum​ BB536 is involved in maintaining physical condition and alleviating common cold-like symptoms in healthy adults,” said the researchers.

Source: Journal of Functional Foods​

DOI: https://doi.org/10.1016/j.jff.2024.106113​  

“Probiotic Bifidobacterium longum BB536 and its impact on subjective symptoms of physical conditions associated with common cold-like symptoms in healthy adults: A randomized, double-blind, placebo-controlled trial”​

Authors: Chendong Xu, Akari Hiraku et al​.

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