Study of the Effects of Vitamin C on Patients With Type 2 Diabetes
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ClinicalTrials.gov Identifier: NCT00001870 |
Recruitment Status :
Completed
First Posted : November 4, 1999
Last Update Posted : March 4, 2008
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Diabetes is a disease characterized by decreased sensitivity to the action on insulin to promote sugar (glucose) use and blood vessel relaxation (vasodilation) in muscle. Insulin's ability to cause blood vessel relaxation is controlled, in part, by nitric oxide (NO).
Nitric oxide is a substance produced by the cells lining blood vessel walls (endothelium). Increased blood flow to the muscle accounts for increased sugar (glucose) to areas of the body. Therefore, if the cells of blood vessel walls (endothelium) are not functioning properly it may contribute to insulin resistance.
Injections of Vitamin C directly into the arteries have been shown to improve blood vessel reaction to nitric oxide in diabetic patients. Researchers believe this may be due to Vitamin C's ability to increase the levels of nitric oxide in blood vessels.
The goal of this study is to determine the effects of vitamin C on both insulin sensitivity and endothelium function of patients with type 2 diabetes. An additional goal of the study is to determine the effects of vitamin C on patients with vitamin C deficiency.
Patients participating in this study will undergo a series of testes to determine insulin sensitivity and blood vessel reactivity. Patients will be divided into two groups. One group will receive doses of oral vitamin C. The other group will receive doses of a placebo (inactive pill not containing vitamin C). Patients will receive the medications for four weeks and then be tested again for insulin sensitivity and blood vessel reactivity.
Researchers believe that doses of vitamin C in diabetics or patients with vitamin C deficiency will improve insulin sensitivity and function of endothelium. Results gathered form this study may provide information about vitamin C levels in diabetics and may lead to the development of new therapies to treat insulin resistance and endothelium dysfunction.
Condition or disease | Intervention/treatment | Phase |
---|---|---|
Diabetes Mellitus, Non-Insulin Dependent Non-Insulin Dependent | Drug: Acetylcholine | Phase 2 |
Study Type : | Interventional (Clinical Trial) |
Enrollment : | 150 participants |
Primary Purpose: | Treatment |
Official Title: | An Exploratory Study of the Effects of Oral Vitamin C Administration on Insulin Sensitivity and Vascular Reactivity in Subjects With Type 2 Diabetes |
Study Start Date : | January 1999 |
Study Completion Date : | December 2004 |


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Ages Eligible for Study: | Child, Adult, Older Adult |
Sexes Eligible for Study: | All |
Accepts Healthy Volunteers: | Yes |
INCLUSION CRITERIA:
DIABETIC SUBJECTS:
Males and non-pregnant females between the ages of 18 and 65 in good general health except for type 2 diabetes controlled with diet and/or oral hypoglycemic agents.
Patients found to have plasma vitamin C levels less than 40 microliter M, will be enrolled into the protocol and taken off hypoglycemic agents approximately one week prior to each study.
VITAMIN C-DEFICIENT CLINICAL RESEARCH VOLUNTEERS:
Adults between the ages of 18 and 35 in good general health and on no drugs or medications.
EXCLUSION CRITERIA:
ALL SUBJECTS:
Pregnancy, liver disease, pulmonary disease, renal insufficiency, coronary heart disease, heart failure, peripheral vascular disease, coagulopathy, disease predisposing to vasculitis or Raynaud's phenomenon, bleeding disorders, kidney stones, glucose-6-phosphate dehydrogenase deficiency, family history of hemochromatosis/iron overload, platelet count less than 150,000/ml blood, prothrombin time/partial thromboplastin time (PT/PTT) greater than 1 second above the normal range, inability to give informed consent for all procedures, and positive tests for HIV, or hepatitis B or C.
DIABETIC SUBJECTS:
In addition, to the above exclusion criteria, the presence of proteinuria greater than 500 mg/24 hrs, proliferative retinipathy, or diabetic neuropathy
VITAMIN C-DEFICIENT CLINICAL RESEARCH VOLUNTEERS:
All the above exclusion criteria.

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.
Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT00001870
United States, Maryland | |
National Center for Complementary and Alternative Medicine (NCCAM) | |
Bethesda, Maryland, United States, 20892 |
ClinicalTrials.gov Identifier: | NCT00001870 |
Other Study ID Numbers: |
990033 99-AT-0033 |
First Posted: | November 4, 1999 Key Record Dates |
Last Update Posted: | March 4, 2008 |
Last Verified: | December 2004 |
Insulin Resistance Oxidative Stress Antioxidant Endothelial Function |
Glucose Clamp Type 2 Diabetes Vitamin C Deficiency |
Diabetes Mellitus Diabetes Mellitus, Type 2 Glucose Metabolism Disorders Metabolic Diseases Endocrine System Diseases Acetylcholine |
Vasodilator Agents Cholinergic Agonists Cholinergic Agents Neurotransmitter Agents Molecular Mechanisms of Pharmacological Action Physiological Effects of Drugs |