The investigators aim to assess the relationship between objectives markers (of physiological reactivity) recorded using a smartwatch and self-reported subjective outcomes measured using standardized and non-standardized questionnaires recorded in an eDiary; with stress as the model for our assessment utilizing the validated PSS-10 questionnaire.

As personal characteristics such as personality traits, resilience, and grit have been shown to modulate reactivity and mental health status, the investigators aim to explore the modulation of the study outcomes by such personality factors. Furthermore, the investigators aim to explore the association of the study outcomes with the composition and functional potential of the gut microbiome.

Finally, the investigators aim to explore the effects of a nutritional intervention on our outcome measures.

Participants will participate in a decentralized, parallel-group study with a mixed design lasting 8 days (excluding screening and enrollment). A total of 120 participants are divided into low-stress(n=40), and elevated-stress groups (n=80) based on their perceived stress score (PSS-10, cut-off score 13). A subgroup of elevated-stress participants (n=40) will be administered a nutritional intervention for 3 days. Their responses will be compared to another subgroup of elevated-stress participants (n=40) without intervention.

Inclusion Criteria:

• Aged 21 to 30 years
• Own and uses a smartphone that is capable of running the study applications
• Have access to the internet
• Adequate fluency in the English language to understand the informed consent process, study instructions and study assessments
• Sufficient vision and hearing to complete study procedures
• Willing to commit to about 20 minutes of assessments each day for a period of 8 days
• Willing to wear selected study devices 24 hours/day; 7-days per week with only occasional relief
• Willing and able to participate and to give written informed consent

Exclusion Criteria:

• Past (< 6 months prior to the study) or current neurological or psychiatric condition
• Past (< 3 months prior to the study) or current use of psychoactive medication
• Having received antibiotic treatment < 4 weeks prior to the study
• Present or past history of alcohol or drug addiction and/or recreational drug use
• Maltodextrin allergy
• Members of the research team or their immediate family members. An immediate family member is defined as spouse, parent, child, or sibling, whether biological or legally adopted
• Women participants who are currently pregnant or have been pregnant in past 6 months