Upper respiratory tract infections (URTI) are the illnesses caused by an acute infection at nose, sinuses, pharynx or larynx. These are generally called common cold. Since HK L-137 enhances the Th1-type immune responses, it is expected that HK L-137 exerts a protective effect against URTI in humans.
To examine the effects of intake of HK L-137 on the symptoms of URTI and immune functions, a randomized, double-blind, placebo-controlled, parallel study was conducted in healthy subjects with high levels of psychological stress. As a result, daily intake of HK L-137 decreased the incidence and severity of URTI in healthy subjects through augmentation of immunity.
[Subjects]
Seventy eight healthy subjects (33 men and 45 women, mean age 50.6 ys) with scores ≥ 42 for 18-item sub-scales of psychological distress in the Japan Brief Job Stress Questionnaire participated in this study.
[Study design]
Seventy eight healthy subjects were enrolled in a randomized, double-blind, placebo-controlled, parallel study and were randomly assigned into two groups (HK L-137: N=39, Placebo: N=39). These subjects consumed a tablet containing 10 mg of HK L-137 (1 tablet/d), or a matching placebo tablet for 12 wks.
[End points]
The URTI symptoms were rated once daily on the validated 21-item Wisconsin Upper Respiratory Symptom Survey-21. Days on which subjects took anti-inflammatory medications were checked. T cell proliferation of peripheral blood mononuclear cells in the subjects who were not affected with URTI during the study was measured every 4 wk.
T cell proliferation was significantly higher in the HK L-137 group than in the control group during the study. Moreover, the incidence of URTI in the HK L-137 group was significantly lower than that in the control group and the days of medication showed a significant negative correlation with duration of HK L-137 intake.
T cell proliferation
T cell proliferation was measured at every 4 wk, and percentage changes from baseline in each group are shown.
T cell proliferation was significantly higher in the HK L-137 group than in the control group during the study (P=0.017).
Incidence of URTI
The incidences of URTI for every 4 wks in each group are shown.
The incidence of URTI in the HK L-137 group was significantly lower than that in the control group (P=0.011).
Days of medication
The days of medication for every week in each group are shown.
The days of medication showed a significant negative correlation with duration of HK L-137 intake (P=0.008).
These results suggest that daily intake of HK L-137 augments cellular immunity, thereby decreasing the incidence and severity of URTI in healthy subjects.
In this study, the duration (P=0.005), mental (P=0.005) or physical (P=0.007) severity of URTI also showed a significant negative correlation with duration of HK L-137 intake (data not shown).
Intake of HK L-137 may be useful for prevention of URTI to healthy people with an weakened immune function induced by highly levels of psychological stress or by other factors such as aging and physical stress
Reference:J Nutr Sci 2: e39, (2013)(External Link) 
