LAUSR

We investigated the effects of paraprobiotic Lactobacillus paracasei MCC1849 (LAC-Shield™) on symptoms of the common cold and mood states in healthy young adults. A total of 241 participants were randomised to receive 1×1010 heat-killed L. paracasei MCC1849 cell powder (10LP), 3×1010 heat-killed L. paracasei MCC1849 cell powder (30LP), or placebo powder without any L. paracasei cells once daily for 12 weeks based on the incidence of the common cold in the previous year, so that the risk of the incidence was equal among the groups. The incidence and severity of common cold symptoms were rated daily in a subject diary. Salivary secretory immunoglobulin A concentrations and saliva flow rates were analysed at 0 and 6 weeks. The Profile of Mood States (POMS) was assessed using POMS 2 0, 6, and 12 weeks after the intervention. No significant differences were observed in the incidence of the common cold among the groups. In a prespecified subgroup of subjects who had the common cold in the previous year, the incidence, total number of days of symptoms, and symptom scores of the common cold significantly improved in the 10LP-intake group, and were slightly lower in the 30LP-intake group than in the placebo group. The level of deterioration in the positive mood state caused by stress was less in the MCC1849-intake group than in the placebo group. These results indicate that L. paracasei MCC1849 has the potential to improve resistance to common cold infections in susceptible subjects and maintain a desirable mood state, even under mental stress conditions. Further randomised controlled trials are needed in order to investigate the possible beneficial effects of paraprobiotic L. paracasei MCC1849 on the common cold in susceptible populations.