Coffee Consumption, the Gut Microbiome, and the Microbiota-Gut-Brain Axis

The aim of this study is to investigate the potential of coffee to act as a prebiotic to alter gut microbiota and improve mood, memory and cognitive performance. Additional gut-brain axis pathways-related parameters such as inflammation, short chain fatty acids and other metabolites production and physiological stress levels will be explored. Moreover, differences between caffeinated and decaffeinated coffee consumption will be investigated to determine whether observed effects are attributed to caffeine or other coffee components.

To determine the mechanism of action underlying the beneficial effects of coffee, coffee drinkers abstained from coffee and caffeine for a 2-week washout period following the baseline visit. Coffee drinkers further underwent an intervention in which they consumed either 4 sachets (1.8 grams each) of instant caffeinated or decaffeinated coffee per day for 3 weeks of using a double-blind, randomised, parallel design. Reaction time, socioemotional processing, visual and episodic memory, learning, and an attentional task were administered to measure cognitive performance. Self-report questionnaires on mood, behavior and lifestyle were administered and response to an acute stressor was assessed. Biological samples of saliva, urine, blood, and stool were collected to investigate microbiome-gut-brain-axis signaling.

Inclusion criteria

• Be able to give written informed consent.
• Be between 30 and 50 years of age.
• Be in generally good health as determined by the investigator.
• Drink moderate amounts of coffee daily (3-5 cups/day)

Exclusion criteria

• Are less than 30 and greater than 50 years of age.
• 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.
• Be hypertensive.
• Current prebiotic or probiotic supplement use (a wash-out period of 4 weeks after cessation will allow entry to the study), or habitual consumption of foods deemed by the investigator to be particularly rich in prebiotic fibres or probiotic strains or are vegan.
• Females who are pregnant or planning a pregnancy, or lactating.
• Participants who are not fluent in English.
• Participants who 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 already done a study in the lab in the past 4 years