An interventional study of Low, High Fiber Diet and High, Low Fiber Diet in Healthy Adults and Dietary Fiber Fermentation, sponsored by Örebro University, Sweden. Recruiting at 1 site in Sweden. Open to participants aged 18 Years to 65 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-06-04.
Sponsored by Örebro University, Sweden · Not applicable, Interventional, and Basic science
The aim of this crossover intervention study is to evaluate the volatile organic compounds (VOCs) present in participants at baseline and how these levels change after consuming either a low- or high-dietary fiber diet for three days. This study will involve adults, 18-65 years old, without any gastrointestinal diseases.
The primary objectives are to characterize baseline VOC profiles, assess changes in these profiles after a short-term dietary fiber intervention, determine if specific VOC patterns correlate with dietary fiber intake, and identify the time points at which VOC levels peak. This information will help establish the optimal timing for breath sampling and potentially provide insight into how VOC patterns relate to dietary fiber consumption and degradation.
The expected outcome is that a high-dietary fiber diet will produce a VOC profile enriched in metabolites associated with fiber fermentation compared to a low-dietary fiber diet, and that these VOCs will be consistent with those identified in vitro during fecal fermentation. Each participant will serve as an internal control, enabling within-subject comparisons of VOC levels at baseline and following the dietary fiber intervention.
Participants will receive a whole-food product that is rich in dietary fiber and will consume either a low-fiber diet (10 g/day) or a high-fiber diet (40 g/day) for three days. On the first day of each intervention, participants will also ingest a pH capsule to monitor gastrointestinal pH continuously throughout the three days. After a three-week washout period, participants will cross over to the other intervention arm and undergo another round of gastrointestinal pH monitoring.
In addition to the dietary intervention, participants will complete food and health questionnaires to assess habitual fiber intake and dietary habits. Fecal samples will be collected for in vitro fermentation to functionally profile the gut microbiota by assessing fecal VOCs, short-chain fatty acids (SCFA), and the microbial enzymatic activity and its pH-dependent modulation.
Örebro University, Sweden is the lead sponsor of 86 studies on the registry; 14 are open to participants now.
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Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
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You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants will receive a whole food dietary fiber product to consume 10g of dietary fiber per day over a total of 3 days, equal to a high fiber diet. After a washout period of 3 weeks, they then receive the same whole food dietary fiber product, to consume 40g of dietary fiber per day in a total of 3 days, equal to a high fiber diet.
Other: Low, High Fiber Diet
Participants will receive a whole food dietary fiber product to consume 40g of dietary fiber per day over a total of 3 days, equal to a high fiber diet. After a washout period of 3 weeks, they then receive the same whole food dietary fiber product, to consume 10g of dietary fiber per day in a total of 3 days, equal to a high fiber diet.
Other: High, Low Fiber Diet
Dietary Intervention: Low Fiber Diet Whole food dietary fiber product, 10g of dietary fiber consumed per day for 3 days Dietary Intervention: High Fiber Diet Whole food dietary fiber product, 40g of dietary fiber consumed per day for 3 days
Dietary Intervention: High Fiber Diet Whole food dietary fiber product, 40g of dietary fiber consumed per day for 3 days Dietary Intervention: Low Fiber Diet Whole food dietary fiber product, 10g of dietary fiber consumed per day for 3 days
Effect of a 3-day low fiber diet compared to a 3-day high fiber diet on the Volatile Organic Compound profiles in exhaled breath
Volatile Organic Compound profiles in produced by the 3-day low fiber diet intervention compared to the profiles produced by the 3-day high fiber diet, with a 3-week washout inbetween
Time frame: 5 weeks
Effect of a low fiber diet on Volatile Organic Compound profiles after 4 hours
Volatile organic compound profiles 4 hours after the start of the low fiber diet intervention compared with baseline (0 hours)
Time frame: 4 hours
Effect of a low fiber diet on Volatile Organic Compound profiles after 6 hours
Volatile organic compound profiles 6 hours after the start of the low fiber diet intervention compared with baseline (0 hours)
Time frame: 6 hours
Effect of a low fiber diet on Volatile Organic Compound profiles after 8 hours
Volatile organic compound profiles 8 hours after the start of the low fiber diet intervention compared with baseline (0 hours)
Time frame: 8 hours
Effect of a high fiber diet on Volatile Organic Compound profiles after 4 hours
Volatile organic compound profiles 4 hours after the start of the high fiber diet intervention compared with baseline (0 hours)
Time frame: 4 hours
Effect of a high fiber diet on Volatile Organic Compound profiles after 6 hours
Volatile organic compound profiles 6 hours after the start of the high fiber diet intervention compared with baseline (0 hours)
Time frame: 6 hours
Effect of a high fiber diet on Volatile Organic Compound profiles after 8 hours
Volatile organic compound profiles 8 hours after the start of the high fiber diet intervention compared with baseline (0 hours)
Time frame: 8 hours
Gastrointestinal pH after a 3-day low fiber diet
Assessment of Gastrointestinal pH measured by the alpHaONE JSPC-1 pH capsule, after a 3-day low fiber diet
Time frame: 5 weeks
Gastrointestinal pH after a 3-day high fiber diet
Assessment of Gastrointestinal pH measured by the alpHaONE JSPC-1 pH capsule, after a 3-day high fiber diet
Time frame: 5 weeks
Fecal Volatile Organic Compound profiles
Changes in fecal Volatile Organic Compound profiles produced during fecal fermentation, comparison of baseline (0 hours) profiles with profiles at 24 hours
Time frame: 1 week
SCFA
Changes in SCFA levels produced during fecal fermentation, comparison of baseline (0 hours) levels with levels at 24 hours
Time frame: 1 Week
Microbial enzymatic activity
Changes in microbial enzymatic activity during fecal fermentation, comparison of baseline (0 hours) activity with activity at 24 hours
Time frame: 1 week
Microbiota composition
Microbiota composition at baseline (0 hours) compared with composition at 24 hours
Time frame: 1 week
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Örebro University, Sweden