Interactions Between Diet, Microbiome and Abiotic Conditions in the Gut

The aim of this study is to explore the interplay between environmental (abiotic) factors in the gut and the gut microbiota composition, diversity and metabolism. Such insights could help us understand personal responses to diets and be a first step towards personalized dietary recommendations targeting the gut microbiome.

The study is a 9-day trial including 85 healthy adults in age between 18 and 75. The participants will throughout the trial register their dietary intake, gastrointestinal symptoms including stool frequency and Bristol stool scale, physical activity, and medicine and supplements intake. Participants will on day 3 and day 5, respectively, consume sweet corns to estimate intestinal transit time by the time it takes sweet corn to travel through the gastrointestinal system. Furthermore, the participants will collect daily urine and stool samples.

On day 2 and day 9, participants will arrive fasting at the department in the morning and have their anthropometry, breath hydrogen and methane levels measured, and a blood sample will be collected from each participant.

The first visit (day 2) also includes a standardized meal test (rye bread, butter, jam, egg, and yogurt with nuts and berries) and intake of paracetamol (250 mg). Subsequently, the participants will stay at the department for the following 6 hours and have their postprandial breath hydrogen and methane measured and urine collected at specific intervals.

Moreover, a sub-set of the participants will on the first visit (day 2) immediately after intake of the standardized meal swallow a single-use gastrointestinal SmartPill capsule, which will monitor their gastrointestinal pH, transit time, temperature and pressure.

Eligibility Criteria:
Inclusion Criteria:

* 18.5-30.0 kg/m2 BMI
* Willing to daily collect a urine and stool sample at home and able to store them in their own freezer in a provided containers throughout the 9-days trial
* Willing to eat sweet corn and report corn-intestinal transit time questionnaire
* Willing to record 9 days dietary intake and defecation pattern
* Willing to have blood samples drawn two times
* Owns a device with access to the internet and is willing to use myfood24 platform
* Known ability to tolerate paracetamol and willing to consume ½ paracetamol tablet dissolved in water (250mg)
* Willing to eat rye bread, butter, jam, egg, yoghurt, berries and nuts

Exclusion Criteria:

* Any condition that makes the project responsible researcher to doubt the feasibility of the volunteer´s participation
* Pregnant or lactating women
* Suffering from inflammatory bowel syndrome (IBS), small intestinal bacterial overgrowth (SIBO) or inflammatory bowel diseases (IBD)
* Intake of antibiotics, diarrhea inhibitors and laxatives ˂ 1month
* Current chronic or infectious diseases
* Diagnosis of diabetes
* History of cancer within the past 5 years (except adequately-treated localized basal cell skin cancer or in situ uterine cervical cancer)
* Frequent intake of painkillers or other medication (mild antidepressants and contraceptive pills are allowed)
* Concurrent participation in another trial

Additional exclusion criteria for the SmartPill sub-study:

* Intake of medications potentially altering gastric pH (proton pump inhibitors, histamine receptor antagonists, antacids)
* Intake of medications potentially altering the gastrointestinal motility (prokinetics, antiemetic agents, anticholinergic agents, narcotic analgetics, nonsteroidal anti-inflammatory drugs)
* Dysphagia