Table 1.

Exclusion criteria for participants.

Relevant, uncorrected vision disorder

Evidence of cognitive impairment (ACE-III score of ≤86)

Relevant psychiatric or neurological pre-existing condition (e.g., major depression, focal damage of the brain due to operation or stroke, epilepsy)

Contraindications for MRI (e.g., cardiac pacemaker, non-removable metal parts in/at the body, claustrophobia)

Permanent medication with sedating substances

Loss of capacity of consent

Relevant, physical impairment

Stadium 3 and 4 cardiac diseases

Relevant systemic disease: cancer, severe kidney or liver disease, type 1 or 2 diabetes, diseases with intrinsic inflammation (e.g., arthritis, Crohn’s disease, asthma, chronic infections)

Treatments that influence glucose or microbiome composition: antidiabetics, antibiotics, immune suppressants, etc.

Chronic obstipation or diarrhea

Symptoms of clinical infection during the last month

Excessive alcohol/drug consumption

Severe eating disorder

Known disruption of iron balance

Chronic treatment with steroidal anti-inflammatory drugs

Treatment with proton pump inhibitors