title: Fermented milk containing Lactobacillus casei strain Shirota prevents the onset of physical symptoms in medical students under academic examination stress.
abstract: This pilot study investigated the effects of the probiotic Lactobacillus casei strain Shirota (LcS) on psychological, physiological, and physical stress responses in medical students undertaking an authorised nationwide examination for promotion. In a double-blind, placebo-controlled trial, 24 and 23 healthy medical students consumed a fermented milk containing LcS and a placebo milk, respectively, once a day for 8 weeks until the day before the examination. Psychophysical state, salivary cortisol, faecal serotonin, and plasma L-tryptophan were analysed on 5 different sampling days (8 weeks before, 2 weeks before, 1 day before, immediately after, and 2 weeks after the examination). Physical symptoms were also recorded in a diary by subjects during the intervention period for 8 weeks. In association with a significant elevation of anxiety at 1 day before the examination, salivary cortisol and plasma L-tryptophan levels were significantly increased in only the placebo group (P<0.05). Two weeks after the examination, the LcS group had significantly higher faecal serotonin levels (P<0.05) than the placebo group. Moreover, the rate of subjects experiencing common abdominal and cold symptoms and total number of days experiencing these physical symptoms per subject were significantly lower in the LcS group than in the placebo group during the pre-examination period at 5-6 weeks (each P<0.05) and 7-8 weeks (each P<0.01) during the intervention period. Our results suggest that the daily consumption of fermented milk containing LcS may exert beneficial effects preventing the onset of physical symptoms in healthy subjects exposed to stressful situations.
authors.affiliation: 1 Yakult Central Institute, 5-11 Izumi, Kunitachi, Tokyo 186-8650, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Kato-Kataoka
authors.affiliation: 2 Department of Pathophysiology, Tokushima University Graduate School of Medicine, 3-18-5 Kuramoto, Tokushima, Tokushima 770-8503, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Nishida
authors.affiliation: 1 Yakult Central Institute, 5-11 Izumi, Kunitachi, Tokyo 186-8650, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Takada
authors.affiliation: 1 Yakult Central Institute, 5-11 Izumi, Kunitachi, Tokyo 186-8650, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Suda
authors.affiliation: 1 Yakult Central Institute, 5-11 Izumi, Kunitachi, Tokyo 186-8650, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Kawai
authors.affiliation: 1 Yakult Central Institute, 5-11 Izumi, Kunitachi, Tokyo 186-8650, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Shimizu
authors.affiliation: 1 Yakult Central Institute, 5-11 Izumi, Kunitachi, Tokyo 186-8650, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Kushiro
authors.affiliation: 3 Faculty of Research and Development, Yakult Honsya Co., Ltd., 1-1-19 Higashi-Shimbashi, Minato, Tokyo 105-8660, Japan.
authors.forename: R
authors.initials: R
authors.lastname: Hoshi
authors.affiliation: 3 Faculty of Research and Development, Yakult Honsya Co., Ltd., 1-1-19 Higashi-Shimbashi, Minato, Tokyo 105-8660, Japan.
authors.forename: O
authors.initials: O
authors.lastname: Watanabe
authors.affiliation: 3 Faculty of Research and Development, Yakult Honsya Co., Ltd., 1-1-19 Higashi-Shimbashi, Minato, Tokyo 105-8660, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Igarashi
authors.affiliation: 1 Yakult Central Institute, 5-11 Izumi, Kunitachi, Tokyo 186-8650, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Miyazaki
authors.affiliation: 2 Department of Pathophysiology, Tokushima University Graduate School of Medicine, 3-18-5 Kuramoto, Tokushima, Tokushima 770-8503, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Kuwano
authors.affiliation: 2 Department of Pathophysiology, Tokushima University Graduate School of Medicine, 3-18-5 Kuramoto, Tokushima, Tokushima 770-8503, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Rokutan
mesh_terms: D000818:Animals; D001007:Anxiety / Q000378:metabolism / Q000503:physiopathology / Q000517:prevention & control* / Q000523:psychology; D043302:Cultured Milk Products / Q000032:analysis*; D004311:Double-Blind Method; D005260:Female; D005285:Fermentation; D006801:Humans; D007780:Lacticaseibacillus casei / Q000378:metabolism*; D008297:Male; D008892:Milk / Q000378:metabolism / Q000382:microbiology*; D019936:Probiotics / Q000378:metabolism; D013312:Stress, Physiological; D013337:Students, Medical / Q000523:psychology; D014364:Tryptophan / Q000378:metabolism; D055815:Young Adult
chemical_list: D014364:Tryptophan
keywords: physical symptoms; probiotics; salivary cortisol; serotonin; tryptophan