Fermented milk of Lactobacillus helveticus IDCC3801 improves cognitive functioning during cognitive fatigue tests in healthy older adults

•We investigate the effects of Lactobacillus helveticus-fermented milk in elderly.•We examine changes on cognitive function, PSS, BDNF, GDS-SF, BDNF, and WBV.•The LHFM produced improvement on cognitive tests compared to the placebo group.•No significant effects were observed for PSS, GDS-SF, BDNF, and WBV. Probiotics are consumed in a wide variety of fermented foods to improve health. This study was conducted to investigate the effects of Lactobacillus helveticus-fermented milk (LHFM), on cognitive function in healthy older adults. A 12-week, double-blind, randomized controlled experiment was conducted. Cognitive tests (neuropsychological and cognitive fatigue) and measurements of the perceived stress scale (PSS), geriatric depression scale-short form (GDS-SF), brain-derived neurotrophic factor (BDNF) and whole blood viscosity (WBV) were conducted before and after the experiment. The administration of LHFM for 12 weeks in healthy older adults produced improvement on cognitive tests compared to the placebo group. However, no significant effects were observed for PSS, GDS-SF, BDNF, and WBV. Thus, consumption of LHFM might be beneficial for improving cognitive function.