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The Body's Affect on Vitamin C

This study is currently recruiting participants. (see Contacts and Locations)
Verified March 23, 2017 by National Institutes of Health Clinical Center (CC)
Information provided by (Responsible Party):
National Institutes of Health Clinical Center (CC) ( National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) ) Identifier:
First received: November 3, 1999
Last updated: April 21, 2017
Last verified: March 23, 2017

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.

Healthy Volunteers

Study Type: Observational
Study Design: Observational Model: Cohort
Time Perspective: Prospective
Official Title: Pharmacokinetics and Biodistribution of Ascorbic Acid in Healthy Human Subjects

Resource links provided by NLM:

Further study details as provided by National Institutes of Health Clinical Center (CC):

Primary Outcome Measures:
  • Changes in ascorbic acid concentrations [ Time Frame: 5 years ]

Estimated Enrollment: 50
Study Start Date: October 25, 1991
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.


Ages Eligible for Study:   18 Years to 35 Years   (Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes
  • 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:

  1. Spend within a fall or spring semester (approximately 20-26 weeks) as an inpatient resident on the endocrine-metabolic ward at NIH.
  2. Be willing to adhere to an ascorbate restricted diet for the duration of the time spent in the study as an inpatient at NlH.
  3. Have veins adequate for venipunctures and be willing to undergo venipunctures approximately two to three times per week.
  4. Refrain from ingestion of any medication and cigarette smoking and ethanol.
  5. Be able to give informed consent.


  1. Subject non-compliance with restricted diet.
  2. Pregnancy as determined by history, physical exam and urine b-HCG.
  3. History of diabetes mellitus, bleeding disorders, kidney stones, glucose-6- phosphate dehydrogenase deficiency, family history of hemochromatosis/iron overload.
  4. Platelet count <150,000/ul blood; prothrombin time/partial thromboplastin time (PT/PTT) > 1 second above normal upper limit.
  5. Positive test for exposure to human immunodeficiency virus.
  6. Positive tests for hepatitis B surface antigen, core antibody or surface antibody.
  Contacts and Locations
Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the Contacts provided below. For general information, see Learn About Clinical Studies.

Please refer to this study by its identifier: NCT00001309

Contact: Mark A Levine, M.D. (301) 402-5588

United States, Maryland
National Institutes of Health Clinical Center, 9000 Rockville Pike Recruiting
Bethesda, Maryland, United States, 20892
Contact: For more information at the NIH Clinical Center contact Patient Recruitment and Public Liaison Office (PRPL)    800-411-1222 ext TTY8664111010   
Sponsors and Collaborators
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Principal Investigator: Mark A Levine, M.D. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
  More Information

Additional Information:
Responsible Party: National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) Identifier: NCT00001309     History of Changes
Other Study ID Numbers: 920033
Study First Received: November 3, 1999
Last Updated: April 21, 2017

Keywords provided by National Institutes of Health Clinical Center (CC):
Ascorbic Acid

Additional relevant MeSH terms:
Ascorbic Acid
Molecular Mechanisms of Pharmacological Action
Protective Agents
Physiological Effects of Drugs
Growth Substances processed this record on May 24, 2017