Lactobacillus plantarum HOKKAIDO (HOKKAIDO strain) was isolated from well-pickled vegetables in
Hokkaido, Japan. We report a randomized, double-blind, placebo-controlled study evaluating the effects
of L. plantarum HOKKAIDO on immune function and stress markers in 171 adult subjects. Subjects were
divided into three groups: the L. plantarum HOKKAIDO yogurt group, the placebo-1 group who ingested
yogurt without the HOKKAIDO strain, and the placebo-2 group who ingested a yogurt-like dessert
without the HOKKAIDO strain. Hematological tests and body composition measurements were performed
before and after 4 and 8 weeks of blinded ingestion. Although no significant differences in
natural killer cell activity were observed, it was found that neutrophil ratio significantly decreased and
lymphocytes tended to increase in the HOKKAIDO strain yogurt group compared with the yogurt-like
dessert group. In addition, the neutrophil-to-lymphocyte ratio, a stress marker, tended to improve in
the HOKKAIDO strain yogurt group compared with the yogurt-like dessert group. These results suggest
that the ingestion of HOKKAIDO strain yogurt tends to improve immune activity and decrease stress
markers.