Healthy VolunteersPhase 1NCT00001309
The Body's Affect on Vitamin C
A Phase 1 study testing Vitamin C in people with Healthy Volunteers, run by National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) at 1 site in United States.
Trial summary
Pharmacokinetics is the term used for how the body affects a drug once it is taken. Vitamin C, also known as ascorbic acid, is an essential water soluble vitamin. Meaning, the body does not make Vitamin C it must be taken in through the diet. Read more about this study
- Who is it for?
- Ages 18 to 35 years
- Conditions the study is for
- Healthy Volunteers
- What is being tested?
- Vitamin C
- Type of treatment
- Pill or oral medicine, Injection or infusion
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 23 participants
- Where
- 1 siteUnited States
- Study dates
- 23 Jan 1997to 4 Mar 2019
- Phase
- Phase 1
- 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 to 35 years
- All sexes
- No healthy volunteers
- Adult
Who may be able to join
- 10 Males - ages 18 - 35 yrs
- 10 Females - ages 18 - 35 yrs
- No more than 4 subjects during any period will remain as inpatients on the endocrine/metabolic ward. These subjects will be normal volunteers selected from colleges/universities who will:
- Spend within a fall or spring semester (approximately 20-26 weeks) as an inpatient resident on the endocrine-metabolic ward at NIH.
- Be willing to adhere to an ascorbate restricted diet for the duration of the time spent in the study as an inpatient at NlH.
- Have veins adequate for venipunctures and be willing to undergo venipunctures approximately two to three times per week.
- Refrain from ingestion of any medication and cigarette smoking and ethanol.
- Be able to give informed consent.
Who cannot join
- Subject non-compliance with restricted diet.
- Pregnancy as determined by history, physical exam and urine b-HCG.
- History of diabetes mellitus, bleeding disorders, kidney stones, glucose-6- phosphate dehydrogenase deficiency, family history of hemochromatosis/iron overload.
- Platelet count <150,000/ul blood; prothrombin time/partial thromboplastin time (PT/PTT) > 1 second above normal upper limit.
- Positive test for exposure to human immunodeficiency virus.
- Positive tests for hepatitis B surface antigen, core antibody or surface antibody.
Trial locations and contacts
1 site in 1 country.
United States1 site
National Institutes of Health Clinical Center
Bethesda, Maryland, 20892
About this study
Official title: Pharmacokinetics and Biodistribution of Ascorbic Acid in Healthy Human Subjects
Pharmacokinetics is the term used for how the body affects a drug once it is taken. Vitamin C, also known as ascorbic acid, is an essential water soluble vitamin. Meaning, the body does not make Vitamin C it must be taken in through the diet. In this study researchers will attempt to determine how the amount of water consumed affects the level of vitamin C in the blood (specifically the plasma component of the blood).
In this study researchers will take 13 subjects and place them on a Vitamin C restricted diet. Vitamin C levels will be measured twice a week on an outpatient basis until all subjects reach a desired low level of Vitamin C (12-15 micromolar plasma ascorbic acid concentration). Subjects will then be admitted and undergo 24 hour blood and urine collection. Following the collection of samples, subjects will then begin to receive Vitamin C orally (by mouth) and intravenously (injected into the vein). The dosage of Vitamin C will gradually increase from 30 mg-2500 mg divided into two daily doses. Blood and urine samples will be collected each time the dose is increased. The study will take approximately 18 weeks after which the subjects will be discharged in healthy condition....
Read the detailed description
Vitamin C (ascorbic acid, ascorbate) is an essential water soluble vitamin. Our studies at NIH were the first to demonstrate in healthy men and women how changes in a vitamin concentration in human plasma vary as a direct function of the amount ingested, over a wide range. ln the present study, we plan to achieve a prescorbutic vitamin C plasma concentration of approximately 5-10 micromolar in healthy human volunteers. We will gradually replete these subjects with incremental doses of vitamin C to measure how their plasma, red blood cell, and leukocyte concentrations will change as a function of the dose. We will also determine whether changes in vitamin C concentration result in changes in gene expression and metabolic profiles (metabolomics, lipidomics, proteomics).
Outpatient subjects will be encouraged to consume vitamin C in foods. As inpatients, vitamin C deficiency will be induced by placing subjects on a tightly restricted scorbutic diet. Plasma vitamin C will be monitored several times per week. When subjects have achieved a plasma ascorbate concentration of 5-10 micromolar, blood sampling and urine collection over 24 hours will be performed. After platelets and leukocytes are collected, ascorbate repletion will begin. Escalating doses of ascorbate will be administered orally and intravenously for the remainder of their inpatient admission. Total daily doses of 30mg, 60mg, 100mg, 200mg, 400mg, 1000mg and 2500mg will be given in two divided doses. Bioavailability of ascorbate will be determined at each dosage increment. When plasma ascorbate concentration reaches steady state for each dose, subjects will undergo 36 hr plasma sampling and a timed 48 hr urine collection. At steady state of each of 4 to 5 doses, an apheresis procedure will be performed for collection of platelets and leukocytes. lt is anticipated subjects will be discharged in healthy condition after 20-26 weeks.
- Conditions
- Healthy Volunteers
- Being tested
- Vitamin C
- Keywords
- Pharmacokinetics, Biodistribution, Ascorbic Acid
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Vitamin COther
Outpatient subjects will be encouraged to consume vitamin C in foods. As inpatients, vitamin C deficiency will be induced by placing subjects on a tightly restricted scorbutic diet. Plasma vitamin C will be monitored several times per week. When subjects have achieved a plasma ascorbate concentration of 5-10 micromolar, blood sampling and urine collection over 24 hours will be performed. After platelets and leukocytes are collected, ascorbate repletion will begin. Escalating doses of ascorbate will be administered orally and intravenously for the remainder of their inpatient admission. Total daily doses of 30mg, 60mg, 100mg, 200mg, 400mg, 1000mg and 2500mg will be given in two divided doses. Bioavailability of ascorbate will be determined at each dosage increment. When plasma ascorbate concentration reaches steady state for each dose, subjects will undergo 36 hr plasma sampling and a timed 48 hr urine collection.
| Study group | Role | What they receive |
|---|---|---|
| Pharmacokinetics and Biodistribution of Ascorbic Acid | Other | Outpatient subjects will be encouraged to consume vitamin C in foods. As inpatients, vitamin C deficiency will be induced by placing subjects on a tightly restricted scorbutic diet. Plasma vitamin C will be monitored several times per week. When subjects have achieved a plasma ascorbate concentration of 5-10 micromolar, blood sampling and urine collection over 24 hours will be performed. After platelets and leukocytes are collected, ascorbate repletion will begin. Escalating doses of ascorbate will be administered orally and intravenously for the remainder of their inpatient admission. Total daily doses of 30mg, 60mg, 100mg, 200mg, 400mg, 1000mg and 2500mg will be given in two divided doses. Bioavailability of ascorbate will be determined at each dosage increment. When plasma ascorbate concentration reaches steady state for each dose, subjects will undergo 36 hr plasma sampling and a timed 48 hr urine collection. Receives: Other: Vitamin C |
What is being measured
The primary outcome is the main question the study is designed to answer.
Changes in ascorbic acid concentrations
In this study researchers will attempt to determine how the amount of water consumed affects the level of vitamin C in the blood (specifically the plasma component of the blood).
Measured: 5 years
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted4 Nov 1999 (estimated)
- Study start23 Jan 1997
- Primary completion25 Aug 1999
- Study completion4 Mar 2019
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Healthy VolunteersStudies of the same condition, open and under way.
- More trials run by National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)The 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 1
- Primary purpose
- Basic science
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Enrolment
- 23 participants (actual)
Sponsor and investigators
- Sponsor type
- US National Institutes of Health
- Responsible party
- Sponsor
- Investigators
- Mark A Levine, M.D., Principal investigator, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT00001309
- Sponsor's protocol ID
- 920033
- Other IDs
- 92-DK-0033
- Status last verified
- 21 Jan 2026
- First submitted
- 3 Nov 1999
- Last updated
- 29 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 29 Oct 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Pharmacokinetics and Biodistribution of Ascorbic Acid in Healthy Human Subjects
- ClinicalTrials.gov ID
- NCT00001309
- Acronym / sponsor ID
- 920033
- Conditions
- Healthy Volunteers
- Keywords
- Pharmacokinetics, Biodistribution, Ascorbic Acid
- Phase
- Phase 1
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 23 participants (actual)
- Lead sponsor
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)US National Institutes of Health
- Study start
- 23 Jan 1997 (actual)
- Primary completion
- 25 Aug 1999 (actual)
- Study completion
- 4 Mar 2019 (actual)
- First posted
- 4 Nov 1999 (estimated)
- 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.
Pharmacokinetics is the term used for how the body affects a drug once it is taken. Vitamin C, also known as ascorbic acid, is an essential water soluble vitamin. Meaning, the body does not make Vitamin C it must be taken in through the diet. In this study researchers will attempt to determine how the amount of water consumed affects the level of vitamin C in the blood (specifically the plasma component of the blood).
In this study researchers will take 13 subjects and place them on a Vitamin C restricted diet. Vitamin C levels will be measured twice a week on an outpatient basis until all subjects reach a desired low level of Vitamin C (12-15 micromolar plasma ascorbic acid concentration). Subjects will then be admitted and undergo 24 hour blood and urine collection. Following the collection of samples, subjects will then begin to receive Vitamin C orally (by mouth) and intravenously (injected into the vein). The dosage of Vitamin C will gradually increase from 30 mg-2500 mg divided into two daily doses. Blood and urine samples will be collected each time the dose is increased. The study will take approximately 18 weeks after which the subjects will be discharged in healthy condition....
Detailed description
Vitamin C (ascorbic acid, ascorbate) is an essential water soluble vitamin. Our studies at NIH were the first to demonstrate in healthy men and women how changes in a vitamin concentration in human plasma vary as a direct function of the amount ingested, over a wide range. ln the present study, we plan to achieve a prescorbutic vitamin C plasma concentration of approximately 5-10 micromolar in healthy human volunteers. We will gradually replete these subjects with incremental doses of vitamin C to measure how their plasma, red blood cell, and leukocyte concentrations will change as a function of the dose. We will also determine whether changes in vitamin C concentration result in changes in gene expression and metabolic profiles (metabolomics, lipidomics, proteomics).
Outpatient subjects will be encouraged to consume vitamin C in foods. As inpatients, vitamin C deficiency will be induced by placing subjects on a tightly restricted scorbutic diet. Plasma vitamin C will be monitored several times per week. When subjects have achieved a plasma ascorbate concentration of 5-10 micromolar, blood sampling and urine collection over 24 hours will be performed. After platelets and leukocytes are collected, ascorbate repletion will begin. Escalating doses of ascorbate will be administered orally and intravenously for the remainder of their inpatient admission. Total daily doses of 30mg, 60mg, 100mg, 200mg, 400mg, 1000mg and 2500mg will be given in two divided doses. Bioavailability of ascorbate will be determined at each dosage increment. When plasma ascorbate concentration reaches steady state for each dose, subjects will undergo 36 hr plasma sampling and a timed 48 hr urine collection. At steady state of each of 4 to 5 doses, an apheresis procedure will be performed for collection of platelets and leukocytes. lt is anticipated subjects will be discharged in healthy condition after 20-26 weeks.
Study design
- Primary purpose
- Basic science
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
| Arm | Type | Receives |
|---|---|---|
| Pharmacokinetics and Biodistribution of Ascorbic Acid | Other | Other: Vitamin COutpatient subjects will be encouraged to consume vitamin C in foods. As inpatients, vitamin C deficiency will be induced by placing subjects on a tightly restricted scorbutic diet. Plasma vitamin C will be monitored several times per week. When subjects have achieved a plasma ascorbate concentration of 5-10 micromolar, blood sampling and urine collection over 24 hours will be performed. After platelets and leukocytes are collected, ascorbate repletion will begin. Escalating doses of ascorbate will be administered orally and intravenously for the remainder of their inpatient admission. Total daily doses of 30mg, 60mg, 100mg, 200mg, 400mg, 1000mg and 2500mg will be given in two divided doses. Bioavailability of ascorbate will be determined at each dosage increment. When plasma ascorbate concentration reaches steady state for each dose, subjects will undergo 36 hr plasma sampling and a timed 48 hr urine collection. |
Who may qualify
- Ages
- 18 to 35 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult
Key inclusion criteria (8 listed)
- 10 Males - ages 18 - 35 yrs
- 10 Females - ages 18 - 35 yrs
- No more than 4 subjects during any period will remain as inpatients on the endocrine/metabolic ward. These subjects will be normal volunteers selected from colleges/universities who will:
- Spend within a fall or spring semester (approximately 20-26 weeks) as an inpatient resident on the endocrine-metabolic ward at NIH.
- Be willing to adhere to an ascorbate restricted diet for the duration of the time spent in the study as an inpatient at NlH.
Key exclusion criteria (6 listed)
- Subject non-compliance with restricted diet.
- Pregnancy as determined by history, physical exam and urine b-HCG.
- History of diabetes mellitus, bleeding disorders, kidney stones, glucose-6- phosphate dehydrogenase deficiency, family history of hemochromatosis/iron overload.
- Platelet count <150,000/ul blood; prothrombin time/partial thromboplastin time (PT/PTT) > 1 second above normal upper limit.
- Positive test for exposure to human immunodeficiency virus.
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 |
|---|---|---|
| Vitamin COutpatient subjects will be encouraged to consume vitamin C in foods. As inpatients, vitamin C deficiency will be induced by placing subjects on a tightly restricted scorbutic diet. Plasma vitamin C will be monitored several times per week. When subjects have achieved a plasma ascorbate concentration of 5-10 micromolar, blood sampling and urine collection over 24 hours will be performed. After platelets and leukocytes are collected, ascorbate repletion will begin. Escalating doses of ascorbate will be administered orally and intravenously for the remainder of their inpatient admission. Total daily doses of 30mg, 60mg, 100mg, 200mg, 400mg, 1000mg and 2500mg will be given in two divided doses. Bioavailability of ascorbate will be determined at each dosage increment. When plasma ascorbate concentration reaches steady state for each dose, subjects will undergo 36 hr plasma sampling and a timed 48 hr urine collection. | Other | Pharmacokinetics and Biodistribution of Ascorbic Acid |
Primary outcome
Changes in ascorbic acid concentrations
Time frame: 5 years
In this study researchers will attempt to determine how the amount of water consumed affects the level of vitamin C in the blood (specifically the plasma component of the blood).
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 29 Oct 2026.
- NIH Clinical Center Detailed Web PageLink provided by the sponsor.
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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.
Mark A Levine, M.D. principal investigator
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 1 study testing Vitamin C in people with Healthy Volunteers, run by National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) 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 8 inclusion and 6 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 29 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.
What does this phase mean?
Phase 1 studies test a treatment in a small group of people for the first time or in a new way, mainly to check safety and find the right dose.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
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?
Changes in ascorbic acid concentrations (time frame: 5 years). 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 29 Oct 2026.