The effects of non-viable Lactobacillus on immune function in the elderly: a randomised, double-blind, placebo-controlled study

Forty-two participants in two nursing homes who were ≥65 years of age were randomised to receive a jelly containing 10 billion heat-killed Lactobacillus paracasei MCC1849 cells (LP group) or a placebo jelly without lactobacilli (placebo group) for 6 weeks. Three weeks after beginning jelly intake, all subjects received an influenza vaccination (A/H1N1, A/H2N3 and B). Blood samples were collected before and after the treatment period. There were no significant differences in immune parameters, including in antibody responses against the vaccination, between the groups. In the subgroup of the oldest old, defined as ≥85 years of age (n = 27), the antibody responses to the A/H1N1 and B antigens, which were impaired in the placebo group, were improved in the LP group. No significant effects of non-viable L. paracasei MCC1849 were observed in the elderly. A possible beneficial effect in the oldest old should be explored in further large-scale studies.