Heat-killed bacteria may benefit immune health

By Stephen Daniells

- Last updated on GMT

Heat-killed bacteria may benefit immune health

Related tags: Common cold, Bacteria

Daily intakes of a heat-treated bacterial strain Lactobacillus pentosus strain b240 may reduce the incidence of the common cold in elderly people, says a new study from Japan.

Writing in the British Journal of Nutrition​, Japanese researchers report that oral intake of the bacterial strain was associated with incidence of the common cold was reduced by up to 39% compared to the placebo group.

“To our knowledge, the present study is the first to show that oral intake of heat-killed lactic acid bacteria dose-dependently reduces the incidence rate of the common cold in elderly adults,”​ wrote researchers from Tokyo Metropolitan Institute of Gerontology and Otsuka Pharmaceutical Company Limited.

The strain is described as being an “anaerobic, non-sporulating, Gram-positive bacterium originally isolated from fermented tea leaves”​. Strains have also been isolated from dairy.


Although the strain seems to be beneficial it is not defined as probiotic because it is heat-killed, and not live. According the FAO/WHO, probiotics are defined as "live microorganisms which when administered in adequate amounts confer a health benefit on the host"​.

The Japanese researchers note that both the European Food Safety Authority (EFSA) and the International Dairy Federation have classified L. pentosus​ as a “safe agent for food use”​.

“Thus, the present study suggests that ​L. pentosus has the potential in contributing to human health and nutrition.”

Study details

Three hundred people were recruited to participate in the randomised, double-blind, placebo-controlled trial. Subjects were randomly assigned to one of three groups: A high or low-dose heat-killed L. pentosus​ group or placebo for 20 weeks.

Results showed that, of the 280 people who completed the study, the incidence of common cold was 29% and 35% in the high and low-dose groups, respectively, and 47% in the placebo group.

In addition, perceptions of general health increased in a dose-dependent manner in both groups, compared to placebo.

Commenting on the potential mechanism, the researchers said that animal data has indicated that the strain may enhance production of Immunoglobulin A (IgA), an antibody that plays an important role in mucosal immunity.

“[Our animal and human data] suggest the possibility that oral intake of b240 has an immunoprotective effect against the common cold via enhancement of salivary SIgA production after the activation of the gut mucosal immune system,”​ they said.

No adverse events were noted in any of the groups, and blood analysis showed no significant differences between the groups.

Source: British Journal of Nutrition
Published online ahead of print, FirstView Articles, doi: 10.1017/S0007114512003753
“Immunoprotective effects of oral intake of heat-killed ​Lactobacillus pentosus strain b240 in elderly adults: a randomised, double-blind, placebo-controlled trial”
Authors: S. Shinkai, M. Toba, T. Saito, et al. 

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