Abstract
Although maintaining the health of elderly individuals and young children in developed countries is very important and desirable, these populations are always at risk of infection due to a poor or weakened immune function. Therefore, we examined the immunostimulatory effects of yogurt, with a focus on the roles of exopolysaccharide (EPS), which is produced by lactic acid bacteria. We selected Lactobacillus delbrueckii ssp. bulgaricus OLL1073R-1 (OLL1073R-1) as a high EPS producer. EPS produced by this strain induced the spleen cells of mice to produce interferon-gamma in an in vitro assay. The oral administration of EPS or yogurt fermented with OLL1073R-1 and Streptococcus thermophilus (OLL1073R-1 yogurt) increased NK cell activity in the spleen cells of mice and prolonged the survival periods of mice infected with an influenza virus. Furthermore, the risk of elderly individuals being infected by the common cold and flu was lower after the consumption of OLL1073R-1 yogurt than after consumption of milk. In healthy male college students, increases in specific antibodies against vaccine antigens were greater after the intake of OLL1073R-1 yogurt than after the intake acidified milk.
