Inclusion Criteria:  is 55-80 years of age His/her native language is Czech Is willing to visit the testing centre four times within half a year Is willing to provide blood, urine and stool samples three times within half a year Is willing to self-administer the probiotic/placebo pill once every day for half a year is self-sufficient (handling finances, travelling without a chaperone, administration of medication, correct phone usage, filling forms, meal preparation) Has good vision; Can read and write, glasses are acceptable Has good hearing to hear and understand all instructions during examination Can walk well (walking aids are acceptable) to attend all the examinations  Exclusion Criteria:  Suffers with disorder(s) of digestive system, primarily gastrointestinal disorders (celiac disease, ulcerative colitis, Crohn's disease, frequent diarrhoea) Had severe neurological difficulties (epilepsy, stroke, severe head trauma, meningitis in the past 10 years, brain surgery, brain tumour, prolonged period(s) in an unconscious state - excluding general anaesthesia) Had been treated/Is currently being treated for the following psychiatric disorders: alcohol/medication/drug of abuse dependance, schizophrenia, psychotic disorder, bipolar disorder Is taking medication for depression or low mood Suffers from internal organ failure (heart, liver or kidney failure etc.) Suffered from an oncological problem (cancer) in the past 5 years Underwent radiotherapy or chemotherapy in the past Underwent a surgery/procedure under general anaesthesia in the past three years or has a planned procedure/surgery under general anaesthesia in the next 6 months over the course of this trial Suffered from hepatitis (hepatitis B, C), HIV or syphilis in the past Had taken any probiotics in the past three months