The aim of this study is to determine if and how the "Probiotic Product" affects functional brain responses in healthy subjects during an emotional- and arithmetic stress task, respectively and in terms of microbe-brain-gut interactions.

The aim of this study is to determine if and how the "Probiotic Product" affects functional brain responses in healthy subjects during an emotional- and arithmetic stress task, respectively and in terms of microbe-brain-gut interactions.

In this randomized double-blind placebo-controlled study, n=22 healthy subjects will receive the following interventions in a crossover fashion, separated by a 4-week wash-out period: 1) Probiotic Formula, 2) placebo. After baseline assessments, study participants will start with a 4-week intervention with the study product or the placebo, followed by a 4-week wash-out period and a subsequent 4-week intervention period (placebo or study product, respectively). fMRI (functional magnetic resonance imaging) scanning during two validated stress tasks will be performed after each of the intervention periods (week 4 and week 12). At the same time points and in addition on the days before the 1st and 2nd intervention (baseline 1 and 2), saliva, blood and faecal samples will be collected. Questionnaire data will be collected and psychological tests and instruments will be performed. For one week at baseline and during the intervention periods (last week), subjects will wear actigraphs to record their physical activity and help assess sleep quality. At baseline, subjects will undergo a carbon dioxide (CO2) challenge test as well as a food diary to record dietary habits.

Inclusion Criteria:

1. Age: Age: 18-65 years, males/females.
2. Signed informed consent -

Exclusion Criteria:

1. Concurrent or recent treatment with drugs affecting intestinal function or mood, e.g., antidepressants (< 12 weeks) or antibiotics (< 12 weeks).
2. Concurrent or recent (< 4 weeks) use of nutritional supplements or herb products affecting intestinal function or mood (e.g. aloe vera, St. John´s Wort, fibers, prebiotics and probiotics).
3. Diagnosis of major psychiatric or somatic disease. 4) Abuse of alcohol or drugs. 5) Recent (< 4 weeks) intake of proton pump inhibitors, proton pump inhibitors, PPIs (e.g., omeprazole).

6) Asthma. 7) Cardiovascular diseases. 8) Epilepsy. 9) Renal failure. 10) Cerebral bleeding or history of cerebral bleeding. 11) Allergic to latex. 12) Pregnancy (assessed by urine test) or breastfeeding. 13) Claustrophobia. 14) Smoking or using tobacco including snuff. 15) Inability to maintain exercise routine and dietary pattern during the study.

16) Consumption of more than 6 cups of coffee/caffeine-containing beverages per day.

17) Professional athlete. 18) Dominant left-hand. 19) Medical implant (e.g., pacemaker). 20) Aneurysm clips in the head. 21) Shunts in the head. 22) Grenade-splinter or metal-splinter in the body (e.g., eyes). 23) Metal or electrodes in the body (e.g., temp-catheter, aorta stent, cochlea implant).

24) Comprehensive tooth-implants or prothesis. 25) Operated in the head. 26) Operated in the heart. 27) Swallowed a video-capsule. 28) Non-corrected astigmatism. 29) Regular intake of systemic corticosteroids and anti-inflammatory medication (including NSAIDs) during the last three months.

30) Visual defect without possibility to use lenses during MRI scanning. 31) Known allergy to milk or soy. 32) Any other reason the investigator feels the subject is not suitable for participation in the study.