Elevation of natural killer cell activity and alleviation of mental stress by the consumption of yogurt containing Lactobacillus gasseri SBT2055 and Bifidobacterium longum SBT2928 in a double-blind, placebo-controlled clinical trial

•Several studies have demonstrated the efficacy of probiotics on human health.•We examined the effect of the yogurt containing two particular probiotics.•NK cell activities for the test yogurt group were elevated.•Serum ACTH levels were significantly decreased by the test yogurt.