This study aims to examine the effects of a 6-week colon-delivered multi-vitamin supplement intervention on cognitive performance and stress levels in military under real-life, stressful working conditions.

The study is a randomized, double-blind, placebo-controlled, parallel trial in a real-life setting (military field exercise). The intervention product is a nutritional supplement, composed of vitamins B2, B3, B6, B9, C, and D3. These vitamins will be delivered in the colon where most of these vitamins can be utilized by the gut microbiota, as they act as cofactors for important cellular functions.

The main study outcome is the backward digit span (DS) score in a cognitive test, during the field exercise as compared to the start of the 6-week supplementation period. Secondary parameters are other cognitive test scores and a combined (z-scored) cognitive performance score. Stress levels will be measured in salivary cortisol and self-perceived stress levels will be derived from the HADS and PSS-10 questionnaire. Other stress biomarkers (e.g. heart rate variability) will be measured by a wearable.

A growing number of professionals work in a type of job that brings psychological or physical stress while requiring optimal alertness and cognitive control, so called vigilance. These professionals are for example found in military contexts. Even a tiny lapse in alertness can carry large risks for themselves and others. Some studies suggest that dietary supplementation interventions can support shifts in the gut microbiome composition, leading to beneficial effects on various aspects of cognitive performance.

The primary objective in this study is to examine the effects of a 6-week colon-delivered multi-vitamin supplement intervention on cognitive performance and stress levels in military under real-life, stressful working conditions. The hypothesis here is that increased delivery of the nutrients in the colon can support the microbe community and complement microbe metabolites production (e.g. Short Chain Fatty Acids) that via the gut-brain axis support cognitive performance. A secondary objective is to investigate whether 6-week supplementation of the colon-delivered multivitamin mix reduces stress levels during the field exercise and cognitive tests.

The study is a randomized, double-blind, placebo-controlled, parallel trial in a real-life setting (military field exercise). The intervention product is a nutritional supplement, composed of vitamins B2, B3, B6, B9, C, and D3. The main study outcome is the backward digit span (DS) score in a cognitive test, during the field exercise as compared to the start of the 6-week supplementation period. Secondary parameters are other cognitive test scores and a combined (z-scored) cognitive performance score. Stress levels will be measured in salivary cortisol and self-perceived stress levels will be derived from the HADS and PSS-10 questionnaire. Other stress biomarkers (e.g. heart rate variability) will be measured by a wearable.

Inclusion Criteria:

• Aged between 18-50 years old
• Participating in military field exercise
• BMI between 18.5 - 30 kg/m2
• Stable body weight (< 5 kg change) over the past 3-months;

Exclusion Criteria:

• Food allergies or other issues with foods that would preclude intake of the study products
• History of gastro-intestinal surgery or gastro-intestinal complaints or gastrointestinal diseases (i.e., diarrhoea, Crohn's disease, ulcerative colitis, irritable bowel syndrome, diverticulosis, stomach or duodenal ulcers)
• Suffering from metabolic, neuro-psychiatric disease (i.e., diabetes, hepatitis, HIV, cancer, epilepsy, major depression, AD(H)D, schizophrenia, etc.)
• Taking medication related to gut diseases or stress
• Being severely immunocompromised (HIV positive, transplant patient, on antirejection medications, on a steroid for >30 days, or chemotherapy or radiotherapy within the last year);
• Use of antibiotics within the previous 3 months
• Not willing to refrain from taking other supplements during the intervention period
• Pregnant, lactating or having a wish to become pregnant during the study
• History of drug and/or alcohol abuse at the time of enrolment
• Using doctor described drugs related to gut or neurological/psychiatric diseases
• Alcohol intake > 3 servings of alcoholic beverages per day
• Planned major changes in lifestyle (i.e. diet, dieting, exercise level, travelling) during the duration of the study
• Suffering from an eating disorder
• Vegetarian/vegan diet or other issues with foods that would preclude intake of the study products
• High fibre diet (i.e. >30 g) based on our fibre intake screening tool
• Receiving treatment involving experimental drugs. If the subject has been in a recent experimental trial, these must have been completed not less than 60 days prior to this study.

Supplements are labeled A and B by a scientist who is not involved in this trial.