An interventional study of Low Oxalate Diet and Carbon-13 Ascorbic Acid Oral Load in Kidney Stone, sponsored by University of Alabama at Birmingham. Active, not recruiting at 1 site in United States. Open to participants aged 19 Years and older, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-06-09.
Sponsored by University of Alabama at Birmingham · Not applicable, Interventional, and Basic science
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.
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.
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Exclusion Criteria:
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.
Dietary Supplement: Low Oxalate Diet · Dietary Supplement: Carbon-13 Ascorbic Acid Oral Load
Subjects will be instructed to ingest a controlled diet low in oxalate for a total of 4 days
Subjects will be instructed to ingest 1mg/kg of carbon-13 ascorbic acid at breakfast, 2 days after initiating the low oxalate controlled diet.
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.
Time frame: Day 4
Plan to share: No
No publications or documents are linked to this record.
This study is active, not recruiting, as verified in Jun 2026. You cannot join it, but the record below documents what was studied.
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University of Alabama at Birmingham