Healthy
Conditions
Keywords
Microbiota-gut-brain axis, Diet, Cognition, Stress, Dietary Fibre, Fermented foods
Brief summary
This study aims to investigate the effects of an 8-week dietary intervention on cognitive function, stress, and the gut microbiota in healthy adults with low fibre intake.
Detailed description
The gut microbiota communicates bidirectionally with the brain via the microbiota-gut-brain axis to influence various aspects of human physiology, including host metabolism, immune function, behaviour, and cognition. Diet is a key modulator of the microbial composition, suggesting that the microbiota could explain the association between poor nutrition and decreasing health of the population. Dietary fibre is the main energy source for the gut microbiota and fundamentally impacts its composition and function. The microbiota-gut-brain axis has been proposed to mediate some of the effects of dietary fibre on the brain, for example through microbial metabolites (e.g., short-chain fatty acids (SCFA)), regulation of the immune system, and the microbial impact on gut hormones and neurotransmitters. Similarly, intake of fermented foods is positively associated with cognitive health and has been shown to alter the microbiota composition and function and exert an anti-inflammatory effect. However, no studies to date have examined the singular and combined effects of fermented and fibrous foods on the gut microbiota, cognition, and emotion. The present study aims to determine the role of diet on the microbiota-gut-brain axis and mental health. Using a randomized-controlled, parallel, single-blinded design, participants consuming a habitually low fibre diet (N=200) will undergo an 8-week dietary intervention. Participants will receive one of four diets (n=50 in each group): high fibre (aim 24-35 grams/day), fermented foods (aim 4-6 portions/day), combined diet of fermented foods and high fibre (aim 25-30g/day of fibre and 3-4 servings/day of fermented foods) or control (dietary education according to national Irish guidelines). Cognitive, psychological, and biological measures will be compared at baseline and endpoint. During the intervention period, individuals will provide repeated faecal samples to assess temporal microbial changes.
Interventions
OTHERFermented Foods
Participants will recieve dietary education to include 4 to 6 portions of fermented foods to their normal diet.
OTHERHigh Fibre
Participants will recieve dietary education to increase their fibre intake to 24-35g/day in their normal diet.
OTHERCombined Diet
Participants will recieve dietary education to increase their fibre intake to 25-30g/day and include 3 to 4 portions of fermented foods to their normal diet.
OTHERControl
Participants will recieve dietary education based on the Irish healthy food pyramid.
Sponsors
University College Cork
Study design
Allocation
RANDOMIZED
Intervention model
FACTORIAL
Primary purpose
BASIC_SCIENCE
Masking
SINGLE (Subject)
Intervention model description
Randomized-controlled, parallel, single-blinded design
Eligibility
Sex/Gender
ALL
Age
18 Years to 50 Years
Healthy volunteers
Yes
Inclusion criteria
* Be able to give written informed consent. * Be between 18 and 50 years of age. * Have a body mass index (BMI) between 18.5-29.9 Kg/m2. * Be in generally good health as determined by the investigator.
Exclusion criteria
* Are less than 18 and greater than 50 years of age. * Have a BMI below 18.5 or above 29.9 Kg/m2. * Have a significant acute or chronic coexisting illness \[cardiovascular, gastrointestinal (GI) \[to include functional GI disorders, inflammatory bowel disease, coeliac disease, lactose intolerance, food allergies\], immunological, psychiatric \[to include formal or as determined by MINI Psychiatric interview, diagnosis of current major depression, anxiety disorder, bipolar spectrum disorder, schizophrenia, other DSM-IV Axis I disorder\], neurodevelopmental disorders, immunological, metabolic disorders \[to include type I or II diabetes\], or any condition which contraindicates, in the investigators judgement, entry to the study, * Have a condition or taking a medication that the investigator believes would interfere with the objectives of the study, pose a safety risk, or confound the interpretation of the study results; all psychoactive medications \[to include anxiolytics, antipsychotics, antidepressants, anticonvulsants, centrally acting corticosteroids, and opioid pain relievers), laxatives, enemas, antibiotics, anti-coagulants, over-the counter non-steroidal anti-inflammatories (NSAIDS). Subjects should have a wash-out period of 4 weeks. * Current prebiotic or probiotic supplement use (a wash-out period of 4 weeks after cessation will allow entry to the study). * Females who are peri-menopausal, menopausal or post-menopausal. * Females who are pregnant or planning a pregnancy, or lactating. * Participants who are not fluent in English. * Are colour blind. * Have dyslexia or dyscalculia. * Are a current habitual daily smoker. * Individuals who, in the opinion of the investigator, are considered to be poor attendees or unlikely for any reason to be able to comply with the trial. * Subjects receiving treatment involving experimental drugs. If the subject has been in a recent experimental trial, these must have been completed not less than 30 days prior to this study. * Have a malignant disease or any concomitant end-stage organ disease. * Have completed a study in our laboratory in the past 4 years.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Trait stress/mood: self-report | Change from baseline at 8 weeks | self-report questionnaires |
| Trait stress/mood: hypothalamic-pituitary-adrenal axis activity | Change from baseline at 8 weeks | Cortisol from saliva samples |
| Responses to acute stress: self-report | Change from baseline at 8 weeks | Self-report questionnaires |
| Responses to acute stress: sympathetic-adrenal-medullary pathway activity | Change from baseline at 8 weeks | Galvanic skin response taken from the skin on the hand |
| Responses to acute stress: hypothalamic-pituitary-adrenal axis activity | Change from baseline at 8 weeks | Cortisol from saliva samples |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Cognitive performance: visual pattern recognition memory | Change from baseline at 8 weeks | Pattern Recognition Memory |
| Cognitive performance: cognitive flexibility | Change from baseline at 8 weeks | Intra-Extra Dimensional Set Shifting |
| Cognitive performance: social cognition | Change from baseline at 8 weeks | Emotion Recognition Task |
| Cognitive performance: working memory | Change from baseline at 8 weeks | Spatial Working Memory |
| Microbiota composition and function | Change from baseline at 8 weeks | Shotgun metagenomics of fecal samples |
| Microbial and host metabolomics | Change from baseline at 8 weeks | Untargeted metabolomics analysis |
| Inflammation | Change from baseline at 8 weeks | Inflammatory markers in lipopolysaccharide stimulated and unstimulated bloods |
| Cognitive performance: affective perceptual bias | Change from baseline at 8 weeks | Emotional Bias Task |
| Cognitive performance: episodic memory | Change from baseline at 8 weeks | Modified Rey Auditory Verbal Learning Test (ModRey) |
| Cognitive performance: decision making | Change from baseline at 8 weeks | Iowa Gambling Task |
| Cognitive performance: emotional inhibition | Change from baseline at 8 weeks | Emotional Stroop |
| Cognitive performance: sustained attention | Change from baseline at 8 weeks | Rapid Visual Information Processing |
Countries
Ireland
Contacts
Primary ContactElizabeth Schneider, PhD
Backup ContactRevathy Munuswamy
Outcome results
None listed