Hydrogen SulfideNCT06802276
Smart Underwear to Measure Diet-Induced Hydrogen Sulfide Production
A study testing High Cysteine Diet and Low Cysteine Diet in people with Hydrogen Sulfide and Gastrointestinal Microbiome, run by University of Colorado, Denver at 1 site in United States.
Trial summary
The purpose of this study is to evaluate the ability of a wearable Smart Underwear prototype device to quantify diet-induced changes in gut microbial hydrogen sulfide (H₂S) production. Read more about this study
- Who is it for?
- Ages 18 years and olderHealthy volunteers can take part
- Conditions the study is for
- Hydrogen Sulfide, Gastrointestinal Microbiome
- What is being tested?
- High Cysteine Diet and Low Cysteine Diet
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 30 participants
- Where
- 1 siteUnited States
- Study dates
- 21 May 2025to 22 Jul 2026
- Phase
- Interventional
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- Generally healthy volunteers defined as having no major known health conditions (e.g., diabetes, cancer, hypertension, etc.).
- Normal bowel movements, with approximately 1 bowel movement reported per day
- Willing to discuss flatus
- Ages >18yrs
- Willing to complete the entire study protocol, i.e. eating all of the food that is provided and completing all required measurements.
Who cannot join
- Self-report or other evidence of diabetes, other endocrine/metabolic abnormality, dyslipidemia, morbid obesity, severe hypertension, chronic kidney disease, liver disease, pulmonary disease, gastrointestinal, and cardiovascular diseases
- Chronic medications for any of the above conditions
- Food allergy that interferes with ability to complete the study
- Food preferences, intolerance, or dietary requirements that would interfere with diet adherence
- Planned dietary changes during the study period
- Lack of appropriate food refrigeration and preparation equipment (e.g.- oven or microwave)
- Pregnancy or planned pregnancy in the next month
- Physical measurements: BMI > 35 kg/m2
Trial locations and contacts
1 site in 1 country.
United States1 site
University of Colorado Anschutz Medical Campus
Aurora, Colorado, 80045
About this study
Official title: Employing Smart Underwear to Measure Gut Microbial Hydrogen Sulfide Production
The purpose of this study is to evaluate the ability of a wearable Smart Underwear prototype device to quantify diet-induced changes in gut microbial hydrogen sulfide (H₂S) production. The core design is a single-site, 2-period, crossover feeding study with 6-day diet periods and an approximately 11-day washout period. Participants are fed each of two isocaloric diets designed to contrast gut microbial H₂S production (i.e., a high cysteine vs. low cysteine diet), in a random order.
Read the detailed description
H₂S is a circulating signaling molecule that plays numerous roles in human physiology. H₂S produced exogenously by the gut microbiota influences human health by modulating systemic H₂S bioavailability in a diet-dependent manner. Several lines of evidence suggest excessive gut microbial H₂S production may be etiologically involved in a wide range of diseases, from colorectal cancer to ulcerative colitis. However, research on the health-relevant effects of gut microbially-produced H₂S has been constrained by technical limitations.
Gap: Current techniques for measuring gut microbial H₂S production are imprecise, invasive, and have limited temporal resolution, hindering the ability to deconvolute how gut microbial H₂S production both affects human health and is influenced by factors such as diet. Gaseous rectal effluent (flatus) is an ideal, yet untapped biospecimen to measure gut microbial H₂S production.
Preliminary Evidence: To enable real time measurements of gut microbial H₂S production in flatus, the investigators are developing a wearable device called "Smart Underwear". The Smart Underwear device is fundamentally different from previous methods used to measure gut microbial H₂S production. The Smart Underwear device uses an array of metal oxide gas sensors coupled with a multi-layer filtration system to selectively measure H₂S by comparing the signal from filtered and unfiltered sensors. The Smart Underwear sensor array is adhered to the outside of a participant's underwear adjacent to the perineum. Through in vitro and human wearing validation, the investigators have demonstrated the feasibility of the Smart Underwear v1 prototype to measure gut microbial H₂S production in flatus and have shown that the device has potential utility in human cohort studies as a non-invasive device.
The long-term goal of this study is to develop a validated Smart Underwear device that measures real time gut microbial hydrogen sulfide (H₂S) production which is responsive to dietary changes and capable of predicting of pathophysiological outcomes.
The investigators will validate the Smart Underwear prototype device using structured dietary modulation of H₂S production.
Aim: Conduct a randomized controlled feeding trial to evaluate the ability of the Smart Underwear device to quantify diet-induced changes in gut microbial H₂S production.
Hypothesis: The investigators hypothesize that the Smart Underwear device will detect higher H₂S concentrations in flatus during a high cysteine dietary intervention compared to a low cysteine dietary intervention.
Methods: The investigators will employ a randomized crossover feeding trial with two arms designed to contrast gut microbial H₂S production by modulating dietary cysteine while controlling other dietary factors (total calories and nutrients). The investigators have conducted extensive background research to determine that modulation of dietary cysteine is the most effective means of producing a diet-induced contrast in H₂S production. Participants will wear the Smart Underwear device during the dietary interventions allowing for a rigorous evaluation of the devices ability to detect diet-induced alterations of gut microbial H₂S production in flatus.
- Conditions
- Hydrogen Sulfide, Gastrointestinal Microbiome
- Being tested
- High Cysteine Diet, Low Cysteine Diet
- Keywords
- Hydrogen Sulfide, H2S, Diet, Cysteine, Gut Microbiome
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
High Cysteine DietOther
A healthy diet pattern which contains high levels of cysteine or cysteine-related compounds. The high and low cysteine diets will be designed by a research dietician to differ primarily in their concentration of cysteine while providing similar levels of calories, protein, fats, carbohydrates, fiber, and several micronutrients. No additional supplementation of cysteine will be used. Examples of high cysteine foods: chicken, eggs, lentils, yogurt, garlic, cheese, soybeans
Low Cysteine DietOther
A healthy diet pattern which contains low levels of cysteine or cysteine-related compounds. The high and low cysteine diets will be designed by a research dietician to differ primarily in their concentration of cysteine while providing similar levels of calories, protein, fats, carbohydrates, fiber, and several micronutrients. The low cysteine diet includes lower-protein food sources. Examples of low cysteine foods: rice, bread, oranges, bananas, lettuce, snow peas, peppers
| Study group | Role | What they receive |
|---|---|---|
| High Cysteine Diet | Active comparator | A dietary pattern designed to have a high level of dietary cysteine Receives: Other: High Cysteine Diet |
| Low Cysteine Diet | Other | A dietary pattern designed to have a low level of dietary cysteine Receives: Other: Low Cysteine Diet |
What is being measured
The primary outcome is the main question the study is designed to answer.
Hydrogen sulfide (H2S)
Participants will be instructed to wear the Smart Underwear device for all waking hours during the baseline and feeding periods except for bathing and exercise. The Smart Underwear device does not need to be worn while sleeping due to the decreased frequency of flatus. Participants will be warned by the Smart Underwear device if the device is not worn for at least 12 hours per day or if the device detects that it is being worn incorrectly. Aggregate metrics from the device will be included in either the on-site or virtual discussions with staff.
Measured: Daily for 6 days during each dietary intervention period (total of 12 days).
Secondary outcomes (5)
Microbiome Activity Index
A high gut microbiome activity is closely correlated with hydrogen gas production, reflected in the increase of both flatus frequency and hydrogen concentration (e.g., accumulated gas can be expelled in a few high-intensity events or through a series of smaller flatus). The investigators derived a Microbiome Activity Index which combines information on the rate of change in hydrogen and hydrogen sulfide, number of flatus events, and time between flatus events.
Measured: Daily for 6 days during each dietary intervention period (total of 12 days).
Gastrointestinal Microbiome
Participants will self-collect fecal samples using the OMNIgut OM-200 and OM-205 kits.100 Microbiome Sample Collection Kits. Shotgun metagenomic sequencing will be performed to measure changes in microbiome composition and diversity.
Measured: The final day of each 6-day dietary intervention period (total of 2 days).
Experienced Symptoms Questionnaire
Participants will complete a questionnaire about symptoms experienced while on each diet, including symptoms related to fall risk (e.g., feeling faint), food intake and output (e.g., bloating, constipation), fluid intake and output (e.g., excessive thirst), and general symptoms (e.g., fatigue or low energy). Participants will be asked to rate each listed symptom as: did not occur, mild, moderate, or severe. Score range 0-67, higher score worse symptoms.
Measured: The final day of each 6-day dietary intervention period (total of 2 days).
Participant Wearing Time
How long participants wear the Smart Underwear device. Participants will be instructed to wear the Smart Underwear device for all waking hours during the feeding intervention periods except during bathing and exercise. The Smart Underwear device does not need to be worn while sleeping due to the decreased frequency of flatus. The Smart Underwear device internally detects and records wear time; aggregated wear time metrics will be collected from the device at the end of each intervention period.
Measured: Daily for 6 days during each dietary intervention period (total of 12 days).
Systolic Blood Pressure (SBP)
Following 5 minutes of resting in a seated position, blood pressure will be measured in triplicate, and the average of the last two readings (in mmHg) will be calculated.
Measured: The final day of each 6-day dietary intervention period (total of 2 days).
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted31 Jan 2025
- Study start21 May 2025
- Primary completion22 Jul 2026
- Study completion22 Jul 2026
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Hydrogen SulfideStudies of the same condition, open and under way.
- More trials run by University of Colorado, DenverThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Other
- Allocation
- Randomised
- Intervention model
- Crossover
- Model description
- The study design is a two-period crossover feeding study, in which participants will be randomly assigned to each of a high cysteine and low cysteine isocaloric diet for a 6-day period each. Additionally, a 3-day baseline period will occur prior to each dietary intervention period. Diet intervention periods will be separated by a washout period. This washout period may vary slightly between participants and will last for a minimum of 9 days and a maximum of 13 days.
- Masking
- Double blind
- Who is masked
- Investigator, Outcomes assessor
- Enrolment
- 30 participants (actual)
Sponsor and investigators
- Lead sponsor
- University of Colorado, Denver
- Sponsor type
- University, hospital or other
- Collaborators
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), University of Maryland, College Park
- Responsible party
- Sponsor
- Investigators
- Noel T Mueller, PhD, Principal investigator, University of Colorado, DenverAndrew B Hall, PhD, Principal investigator, University of Maryland, College Park
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06802276
- Sponsor's protocol ID
- 24-1861
- Other IDs
- R33DK132310-03
- Status last verified
- Oct 2026
- First submitted
- 15 Jan 2025
- Last updated
- 19 Oct 2026
- Results posted
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
Study at a glance
From the registry record, last updated by the sponsor on 19 Oct 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Employing Smart Underwear to Measure Gut Microbial Hydrogen Sulfide Production
- ClinicalTrials.gov ID
- NCT06802276
- Acronym / sponsor ID
- 24-1861
- Conditions
- Hydrogen Sulfide, Gastrointestinal Microbiome
- Keywords
- Hydrogen Sulfide, H2S, Diet, Cysteine, Gut Microbiome
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 30 participants (actual)
- Lead sponsor
- University of Colorado, DenverUniversity, hospital or other
- Collaborators
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), University of Maryland, College Park
- Study start
- 21 May 2025 (actual)
- Primary completion
- 22 Jul 2026 (actual)
- Study completion
- 22 Jul 2026 (actual)
- First posted
- 31 Jan 2025 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
The purpose of this study is to evaluate the ability of a wearable Smart Underwear prototype device to quantify diet-induced changes in gut microbial hydrogen sulfide (H₂S) production. The core design is a single-site, 2-period, crossover feeding study with 6-day diet periods and an approximately 11-day washout period. Participants are fed each of two isocaloric diets designed to contrast gut microbial H₂S production (i.e., a high cysteine vs. low cysteine diet), in a random order.
Detailed description
H₂S is a circulating signaling molecule that plays numerous roles in human physiology. H₂S produced exogenously by the gut microbiota influences human health by modulating systemic H₂S bioavailability in a diet-dependent manner. Several lines of evidence suggest excessive gut microbial H₂S production may be etiologically involved in a wide range of diseases, from colorectal cancer to ulcerative colitis. However, research on the health-relevant effects of gut microbially-produced H₂S has been constrained by technical limitations.
Gap: Current techniques for measuring gut microbial H₂S production are imprecise, invasive, and have limited temporal resolution, hindering the ability to deconvolute how gut microbial H₂S production both affects human health and is influenced by factors such as diet. Gaseous rectal effluent (flatus) is an ideal, yet untapped biospecimen to measure gut microbial H₂S production.
Preliminary Evidence: To enable real time measurements of gut microbial H₂S production in flatus, the investigators are developing a wearable device called "Smart Underwear". The Smart Underwear device is fundamentally different from previous methods used to measure gut microbial H₂S production. The Smart Underwear device uses an array of metal oxide gas sensors coupled with a multi-layer filtration system to selectively measure H₂S by comparing the signal from filtered and unfiltered sensors. The Smart Underwear sensor array is adhered to the outside of a participant's underwear adjacent to the perineum. Through in vitro and human wearing validation, the investigators have demonstrated the feasibility of the Smart Underwear v1 prototype to measure gut microbial H₂S production in flatus and have shown that the device has potential utility in human cohort studies as a non-invasive device.
The long-term goal of this study is to develop a validated Smart Underwear device that measures real time gut microbial hydrogen sulfide (H₂S) production which is responsive to dietary changes and capable of predicting of pathophysiological outcomes.
The investigators will validate the Smart Underwear prototype device using structured dietary modulation of H₂S production.
Aim: Conduct a randomized controlled feeding trial to evaluate the ability of the Smart Underwear device to quantify diet-induced changes in gut microbial H₂S production.
Hypothesis: The investigators hypothesize that the Smart Underwear device will detect higher H₂S concentrations in flatus during a high cysteine dietary intervention compared to a low cysteine dietary intervention.
Methods: The investigators will employ a randomized crossover feeding trial with two arms designed to contrast gut microbial H₂S production by modulating dietary cysteine while controlling other dietary factors (total calories and nutrients). The investigators have conducted extensive background research to determine that modulation of dietary cysteine is the most effective means of producing a diet-induced contrast in H₂S production. Participants will wear the Smart Underwear device during the dietary interventions allowing for a rigorous evaluation of the devices ability to detect diet-induced alterations of gut microbial H₂S production in flatus.
Study design
- Primary purpose
- Other
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Double blind (investigator, outcomes assessor)
- Number of arms
- 2
- Model description
- The study design is a two-period crossover feeding study, in which participants will be randomly assigned to each of a high cysteine and low cysteine isocaloric diet for a 6-day period each. Additionally, a 3-day baseline period will occur prior to each dietary intervention period. Diet intervention periods will be separated by a washout period. This washout period may vary slightly between participants and will last for a minimum of 9 days and a maximum of 13 days.
| Arm | Type | Receives |
|---|---|---|
| High Cysteine Diet | Active comparator | Other: High Cysteine DietA dietary pattern designed to have a high level of dietary cysteine |
| Low Cysteine Diet | Other | Other: Low Cysteine DietA dietary pattern designed to have a low level of dietary cysteine |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (5 listed)
- Generally healthy volunteers defined as having no major known health conditions (e.g., diabetes, cancer, hypertension, etc.).
- Normal bowel movements, with approximately 1 bowel movement reported per day
- Willing to discuss flatus
- Ages >18yrs
- Willing to complete the entire study protocol, i.e. eating all of the food that is provided and completing all required measurements.
Key exclusion criteria (8 listed)
- Self-report or other evidence of diabetes, other endocrine/metabolic abnormality, dyslipidemia, morbid obesity, severe hypertension, chronic kidney disease, liver disease, pulmonary disease, gastrointestinal, and cardiovascular diseases
- Chronic medications for any of the above conditions
- Food allergy that interferes with ability to complete the study
- Food preferences, intolerance, or dietary requirements that would interfere with diet adherence
- Planned dietary changes during the study period
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| High Cysteine DietA healthy diet pattern which contains high levels of cysteine or cysteine-related compounds. The high and low cysteine diets will be designed by a research dietician to differ primarily in their concentration of cysteine while providing similar levels of calories, protein, fats, carbohydrates, fiber, and several micronutrients. No additional supplementation of cysteine will be used. Examples of high cysteine foods: chicken, eggs, lentils, yogurt, garlic, cheese, soybeans | Other | High Cysteine Diet |
| Low Cysteine DietA healthy diet pattern which contains low levels of cysteine or cysteine-related compounds. The high and low cysteine diets will be designed by a research dietician to differ primarily in their concentration of cysteine while providing similar levels of calories, protein, fats, carbohydrates, fiber, and several micronutrients. The low cysteine diet includes lower-protein food sources. Examples of low cysteine foods: rice, bread, oranges, bananas, lettuce, snow peas, peppers | Other | Low Cysteine Diet |
Primary outcome
Hydrogen sulfide (H2S)
Time frame: Daily for 6 days during each dietary intervention period (total of 12 days).
Participants will be instructed to wear the Smart Underwear device for all waking hours during the baseline and feeding periods except for bathing and exercise. The Smart Underwear device does not need to be worn while sleeping due to the decreased frequency of flatus. Participants will be warned by the Smart Underwear device if the device is not worn for at least 12 hours per day or if the device detects that it is being worn incorrectly. Aggregate metrics from the device will be included in either the on-site or virtual discussions with staff.
5 secondary outcomes
Microbiome Activity Index
Time frame: Daily for 6 days during each dietary intervention period (total of 12 days).
Gastrointestinal Microbiome
Time frame: The final day of each 6-day dietary intervention period (total of 2 days).
Experienced Symptoms Questionnaire
Time frame: The final day of each 6-day dietary intervention period (total of 2 days).
Participant Wearing Time
Time frame: Daily for 6 days during each dietary intervention period (total of 12 days).
Systolic Blood Pressure (SBP)
Time frame: The final day of each 6-day dietary intervention period (total of 2 days).
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 19 Oct 2026.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Noel T Mueller, PhD principal investigator
University of Colorado, Denver
Andrew B Hall, PhD principal investigator
University of Maryland, College Park
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing High Cysteine Diet and Low Cysteine Diet in people with Hydrogen Sulfide and Gastrointestinal Microbiome, run by University of Colorado, Denver at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 5 inclusion and 8 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 19 Oct 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Hydrogen sulfide (H2S) (time frame: Daily for 6 days during each dietary intervention period (total of 12 days).). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 19 Oct 2026.