Kidney StoneNCT04603898
Oxalate Formation From Ascorbic Acid
A study testing Low Oxalate Diet and Carbon-13 Ascorbic Acid Oral Load in people with Kidney Stone, run by University of Alabama at Birmingham at 1 site in United States.
Trial summary
The purpose of this basic research study is to determine the contribution of endogenous ascorbic acid (AA) turnover to urinary oxalate excretion in both normal BMI and obese adult non-stone formers and calcium oxalate stone formers. Read more about this study
- Who is it for?
- Ages 19 years and olderHealthy volunteers can take part
- Conditions the study is for
- Kidney Stone
- What is being tested?
- Low Oxalate Diet and Carbon-13 Ascorbic Acid Oral Load
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 90 participants
- Where
- 1 siteUnited States
- Study dates
- 15 Nov 2021to 1 Feb 2027
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
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 19 years and older
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- Able to provide informed consent
- For stone formers: composition of most recent stone > 50% calcium oxalate, no uric acid component
- For stone formers: first time or recurrent calcium oxalate stone former with stone event within the prior 3 years
- Two 24-hour urine collections with urinary 24-hour creatinine excretion within 20% of appropriate ratio of creatinine (mg) / body weigh (kg) for gender
- Willingness to stop supplements (vitamins, Calcium (citrate or carbonate) and other minerals, herbal supplements, nutritional aids, probiotics) for 2 weeks before start and during study
- Willingness to not undertake vigorous exercise during the study
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- Normal fasting blood Comprehensive Metabolic Panel (CMP)
- Willingness to ingest menus prepared in Clinical Research Unit at University of Alabama at Birmingham
- No food allergies or intolerance to any of the foods in study menus
- If on medications for stone prevention (e.g. thiazides, citrate supplementation excluding calcium citrate), they should have been on a stable dose regimen for at least 8 weeks prior to and during screening, with no changes in dosing anticipated during study protocol. If on allopurinol for stone prevention, stop it for 2 weeks prior to screening and this will not be administered during the study as it has anti-oxidant properties.
Who cannot join
- Diabetes
- Gout
- Hypertension
- Estimated Glomerular Filtration Rate (eGFR) less than 60ml/min/1.73m2
- Primary hyperoxaluria
- Nephrotic syndrome
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- Enteric hyperoxaluria
- Renal tubular acidosis
- Primary hyperparathyroidism
- Liver disease
- Auto-immune disorder
- Neurogenic bladder
- Urinary diversion
- Bariatric surgery
- Active malignancy or treatment for malignancy within 12 months prior to screening
- Pregnancy
- Breastfeeding/nursing individuals
- Females of child bearing age who are not able to use an effective method of birth control during the study
- Mental/medical condition that is likely to impede successful study completion
- Illness including flu/common cold/fever 14 days before study and during study
- Diarrhea or other abnormal gastrointestinal event (e.g. abnormal bowel movements) 14 days before study or during study
- Abnormal fasting CMP
Trial locations and contacts
1 site in 1 country.
United States1 site
University of Alabama at Birmingham
Birmingham, Alabama, 35243-3353
About this study
The purpose of this basic research study is to determine the contribution of endogenous ascorbic acid (AA) turnover to urinary oxalate excretion in both normal BMI and obese adult non-stone formers and calcium oxalate stone formers. The studies proposed will use diets of known nutrient composition, a stable isotope of ascorbic acid (13C6-AA) and mass spectrometric techniques to quantify ascorbic acid turnover to oxalate.
Read the detailed description
The purpose of this basic research study is to determine the contribution of endogenous ascorbic acid (AA)turnover to urinary oxalate excretion in both normal BMI and obese adult non-stone formers and calcium oxalate stone formers. The studies proposed will use diets of known nutrient composition, a stable isotope of AA, 13C6-AA, and mass spectrometric techniques to quantify AA turnover to oxalate.
Adults (≥19 years) with and without a history of calcium oxalate kidney stone disease will be recruited from within the greater Birmingham area, and divided into normal BMI (BMI<25 kg/m2) and obese (BMI≥30 kg/m2) groups. Following consent, subjects will meet with a dietitian to ensure willingness to consume controlled diets, and provide fasted blood and 2 x 24 hour urine specimens to determine general health status and adequacy of 24-hour urine collections, respectively.
Eligible subjects will consume a low oxalate controlled diet for 6 days, which will involve 2 days of dietary equilibration followed by oral ingestion of 1 mg/kg carbon-13 AA with breakfast on day 3 and subsequent collection of 4 consecutive 24-hour urine specimens. After the carbon-13 AA load, subjects will return each morning to the Clinical Research Unit for a fasted blood draw, to drop off their 24-hour urine collection, and receive their prepared food. In addition, on day 4, 24 hours after ingesting carbon-13 AA, subjects will collect hourly urine and 1/2 hourly blood samples for 5 hours in the Clinical Research Unit.
- Conditions
- Kidney Stone
- Being tested
- Low Oxalate Diet, Carbon-13 Ascorbic Acid Oral Load
- Keywords
- Oxalate, Calcium oxalate stones, Ascorbic Acid
- Medical subject headings
- Kidney Calculi
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Low Oxalate DietDietary supplement
Subjects will be instructed to ingest a controlled diet low in oxalate for a total of 4 days
Carbon-13 Ascorbic Acid Oral LoadDietary supplement
Subjects will be instructed to ingest 1mg/kg of carbon-13 ascorbic acid at breakfast, 2 days after initiating the low oxalate controlled diet.
| Study group | Role | What they receive |
|---|---|---|
| Controlled Dietary Study | Experimental | Subjects will consume a controlled diet (low in oxalate and ascorbic acid) for six days. After two days of equilibration, subjects will provide a blood sample and ingest an oral load of ascorbic acid (1 mg/kg) with breakfast on Day 3. The following day (Day 4), serial blood and urine collections will occur. On Days 5 through 7, subjects will complete a 24-hr urine collection and blood draw. Receives: Dietary Supplement: Low Oxalate Diet; Dietary Supplement: Carbon-13 Ascorbic Acid Oral Load |
What is being measured
The primary outcome is the main question the study is designed to answer.
Percent contribution of ascorbic acid (AA) to urinary oxalate excretion
On the last day (Day 4) of controlled diet and 24 hours following ingestion of an oral load of carbon-13 AA (1mg/kg), urine and blood will be collected and the levels of carbon 12 and carbon 13 AA and oxalate measured to determine the percent contribution of AA metabolism to urinary oxalate excretion for each subject.
Measured: Day 4
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted27 Oct 2020
- Study start15 Nov 2021
- Primary completion1 Dec 2026 (estimated)
- Study completion1 Feb 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Kidney StoneStudies of the same condition, open and under way.
- More trials run by University of Alabama at BirminghamThe 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
- Basic science
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Enrolment
- 90 participants (actual)
Sponsor and investigators
- Lead sponsor
- University of Alabama at Birmingham
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, John Knight, University of Alabama at Birmingham
- Investigators
- John Knight, PhD, Principal investigator, University of Alabama at Birmingham
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT04603898
- Sponsor's protocol ID
- IRB-300005614
- Other IDs
- R01DK126774
- Status last verified
- Jun 2026
- First submitted
- 21 Oct 2020
- Last updated
- 9 Jun 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 9 Jun 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Oxalate Formation From Ascorbic Acid
- ClinicalTrials.gov ID
- NCT04603898
- Acronym / sponsor ID
- IRB-300005614
- Conditions
- Kidney Stone
- Keywords
- Oxalate, Calcium oxalate stones, Ascorbic Acid
- Study type
- Interventional
- Recruitment status
- Active, not recruiting
- Enrolment
- 90 participants (actual)
- Lead sponsor
- University of Alabama at BirminghamUniversity, hospital or other
- Collaborators
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
- Study start
- 15 Nov 2021 (actual)
- Primary completion
- 1 Dec 2026 (estimated)
- Study completion
- 1 Feb 2027 (estimated)
- First posted
- 27 Oct 2020 (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 basic research study is to determine the contribution of endogenous ascorbic acid (AA) turnover to urinary oxalate excretion in both normal BMI and obese adult non-stone formers and calcium oxalate stone formers. The studies proposed will use diets of known nutrient composition, a stable isotope of ascorbic acid (13C6-AA) and mass spectrometric techniques to quantify ascorbic acid turnover to oxalate.
Detailed description
The purpose of this basic research study is to determine the contribution of endogenous ascorbic acid (AA)turnover to urinary oxalate excretion in both normal BMI and obese adult non-stone formers and calcium oxalate stone formers. The studies proposed will use diets of known nutrient composition, a stable isotope of AA, 13C6-AA, and mass spectrometric techniques to quantify AA turnover to oxalate.
Adults (≥19 years) with and without a history of calcium oxalate kidney stone disease will be recruited from within the greater Birmingham area, and divided into normal BMI (BMI<25 kg/m2) and obese (BMI≥30 kg/m2) groups. Following consent, subjects will meet with a dietitian to ensure willingness to consume controlled diets, and provide fasted blood and 2 x 24 hour urine specimens to determine general health status and adequacy of 24-hour urine collections, respectively.
Eligible subjects will consume a low oxalate controlled diet for 6 days, which will involve 2 days of dietary equilibration followed by oral ingestion of 1 mg/kg carbon-13 AA with breakfast on day 3 and subsequent collection of 4 consecutive 24-hour urine specimens. After the carbon-13 AA load, subjects will return each morning to the Clinical Research Unit for a fasted blood draw, to drop off their 24-hour urine collection, and receive their prepared food. In addition, on day 4, 24 hours after ingesting carbon-13 AA, subjects will collect hourly urine and 1/2 hourly blood samples for 5 hours in the Clinical Research Unit.
Study design
- Primary purpose
- Basic science
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
| Arm | Type | Receives |
|---|---|---|
| Controlled Dietary Study | Experimental | Dietary Supplement: Low Oxalate Diet, Dietary Supplement: Carbon-13 Ascorbic Acid Oral LoadSubjects will consume a controlled diet (low in oxalate and ascorbic acid) for six days. After two days of equilibration, subjects will provide a blood sample and ingest an oral load of ascorbic acid (1 mg/kg) with breakfast on Day 3. The following day (Day 4), serial blood and urine collections will occur. On Days 5 through 7, subjects will complete a 24-hr urine collection and blood draw. |
Who may qualify
- Ages
- 19 years and older
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (10 listed)
- Able to provide informed consent
- For stone formers: composition of most recent stone > 50% calcium oxalate, no uric acid component
- For stone formers: first time or recurrent calcium oxalate stone former with stone event within the prior 3 years
- Two 24-hour urine collections with urinary 24-hour creatinine excretion within 20% of appropriate ratio of creatinine (mg) / body weigh (kg) for gender
- Willingness to stop supplements (vitamins, Calcium (citrate or carbonate) and other minerals, herbal supplements, nutritional aids, probiotics) for 2 weeks before start and during study
Key exclusion criteria (22 listed)
- Diabetes
- Gout
- Hypertension
- Estimated Glomerular Filtration Rate (eGFR) less than 60ml/min/1.73m2
- Primary hyperoxaluria
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 |
|---|---|---|
| Low Oxalate DietSubjects will be instructed to ingest a controlled diet low in oxalate for a total of 4 days | Dietary supplement | Controlled Dietary Study |
| Carbon-13 Ascorbic Acid Oral LoadSubjects will be instructed to ingest 1mg/kg of carbon-13 ascorbic acid at breakfast, 2 days after initiating the low oxalate controlled diet. | Dietary supplement | Controlled Dietary Study |
Primary outcome
Percent contribution of ascorbic acid (AA) to urinary oxalate excretion
Time frame: Day 4
On the last day (Day 4) of controlled diet and 24 hours following ingestion of an oral load of carbon-13 AA (1mg/kg), urine and blood will be collected and the levels of carbon 12 and carbon 13 AA and oxalate measured to determine the percent contribution of AA metabolism to urinary oxalate excretion for each subject.
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 9 Jun 2026.
- Individual participant dataSharing planned: No
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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.
John Knight, PhD principal investigator
University of Alabama at Birmingham
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Low Oxalate Diet and Carbon-13 Ascorbic Acid Oral Load in people with Kidney Stone, run by University of Alabama at Birmingham 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 10 inclusion and 22 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: under way, not looking for participants, as of the sponsor's last update on 9 Jun 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?
This study is still under way. Results are not available in the source record yet.
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?
Percent contribution of ascorbic acid (AA) to urinary oxalate excretion (time frame: Day 4). 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 9 Jun 2026.