Skip to main content

Abstract

The immunomodulatory effects of live or non-viable lactic acid bacteria have been extensively investigated. We reported that oral intake of heat-killed Lactobacillus plantarum L-137 (HK L-137) augmented innate and acquired immunity in mice and human subjects. To examine the effects of HK L-137 intake on upper respiratory tract infection (URTI) symptoms and immune functions in human subjects, a randomised, double-blind, placebo-controlled, parallel study was conducted in subjects with high psychological stress levels. A total of seventy-eight healthy subjects (thirty-three men and forty-five women; mean age 50·6 years) with scores of >41 on eighteen-item subscales of psychological distress in the Brief Job Stress Questionnaire were randomly assigned to receive a tablet containing HK L-137 (10 mg) or a placebo tablet daily for 12 weeks. The URTI symptoms were rated once daily on the validated twenty-one-item Wisconsin Upper Respiratory Symptom Survey-21. Immune functions, such as concanavalin A-induced proliferation and percentages of interferon (IFN)-γ- and IL-4-producing CD4 T cells of peripheral blood mononuclear cells (PBMC), and serum IFN-β concentrations were measured every 4 weeks. URTI incidence was significantly lower in the HK L-137 group than in the control group. URTI incidence, duration and severity, and duration of medication showed significant negative correlations with duration of HK L-137 intake. The percentage change from baseline of concanavalin A-induced proliferation of PBMC was significantly greater in the HK L-137 group than in the control group. These findings suggest that daily HK L-137 intake can decrease URTI incidence in healthy subjects, possibly through augmentation of immune functions.

Keywords: Con A, concanavalin A; HK L-137, heat-killed Lactobacillus plantarum L-137; IFN, interferon; Immune function; Lactobacillus plantarum; PBMC, peripheral blood mononuclear cells; Stress; Th, T helper; URTI, upper respiratory tract infection; Upper respiratory tract infections; WURSS, Wisconsin Upper Respiratory Symptom Survey; WURSS-21, short-form Wisconsin Upper Respiratory Symptom Survey; WURSS-44, long-form Wisconsin Upper Respiratory Symptom Survey; Wisconsin Upper Respiratory Symptom Survey.

Research Insights

SupplementHealth OutcomeEffect TypeEffect Size
Lactobacillus plantarum L-137Improved Immune FunctionBeneficial
Moderate
Lactobacillus plantarum L-137Reduced Incidence of Upper Respiratory Tract InfectionsBeneficial
Large
⬆ Back to top
Pillser
Supplement Research and Comparison Website: evidence-based information about supplements, their benefits, potential risks, and their efficacy.
Receive updates about our products, services, sales, and special offers. Unsubscribe anytime. See our Privacy Policy for details on how we handle your information.

Join Our Community

Use support@pillser.com to get in touch.