ObesityPhase 2NCT00065676
Investigating the Use of Quercetin on Glucose Absorption in Obesity, and Obesity With Type 2 Diabetes
A Phase 2 study testing Quercetin in people with Obesity and Diabetes, run by National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) at 1 site in United States.
Trial summary
Quercetin is a compound naturally found in various foods. It may have some role in the treatment of obesity and diabetes. The purpose of this study is to investigate research volunteers with obesity or obesity with type 2 diabetes to determine whether quercetin affects the way glucose is absorbed by the body. Read more about this study
- Who is it for?
- Ages 18 to 65 years
- What is being tested?
- Quercetin
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 24 participants
- Where
- 1 siteUnited States
- Study dates
- 30 Apr 2010to 6 Aug 2021
- Phase
- Phase 2
- 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 65 years
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Subjects to be recruited for the study will be male and female subjects between the ages of 18 and 65, able to give informed consent, with mild to moderate type 2 diabetes (such that fasting blood sugar <200mg/dl or HbA1C < 8.5), in otherwise good general health, with no other significant illnesses, blood pressure <=160/90 mmHg with or without medication, with no known severe target organ damage. End organ damage includes the following: proliferative retinopathy, serum creatinine >2, ischemic heart disease, congestive heart failure, known gastroparesis, peripheral vascular disease and severe peripheral neuropathy. Diabetic subjects must have a BMI greater than or equal to 30. Subjects will be taken off hypoglycemic agents for 3 to 7 days prior to each part of the study. This is to remove a confounding factor that may affect blood glucose concentrations attained during the OGTT, independent of the effect of quercetin. Whether these oral hypoglycemic agents have physiologically significant interaction with quercetin is not known. Severity of diabetes and biological duration of action of the drug will determine when to initiate this hold (from 3 to 7 days prior to OGTT). During the time that the subjects are off oral hypoglycemic agents, they will monitor their fasting blood glucose daily by glucometer. Therefore, for subjects with diabetes, only those subjects who self-monitor blood glucose are eligible for inclusion. If the fasting blood glucose in the morning exceeds 300 mg/dl, the subject will be withdrawn from the study and appropriate therapy resumed. Obese volunteers, with a BMI greater than or equal to 30, must be in good health, with no known illness. Healthy, normal weight subjects (BMI <25) will also be recruited as control subjects for the sampling study without querecetin. An upper age limit of 65 years was chosen to minimize renal toxicity of quercetin, as GFR declines with age and quercetin might produce mild though reversible renal impairment.
Who cannot join
- Exclusion criteria will include the following: significant digestive abnormalities such as malabsorption or chronic diarrhea; significant organ malfunction including (but not limited to) liver disease, pulmonary disease, ischemic heart disease, heart failure, stroke, peripheral vascular disease, hypertension (BP >160/90), and anemia (hematocrit < 30); other serious or chronic illness; history of serious or chronic illness; any significant complications from diabetes such as kidney damage (renal insufficiency, serum creatinine >2), eye damage (proliferative retinopathy), severe diabetic neuropathy, coronary artery disease, or symptomatic peripheral vascular disease; smoking; alcohol or drug abuse; smokers; pregnancy (a urine pregnancy test will be performed on all women with reproductive age before each part of the study); lactation; positive HIV or hepatitis (B or C) screening tests (subjects will be notified of these test results). Diabetic subjects who choose not to self-monitor glucose daily by glucometer will be excluded.
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: Inhibition of Intestinal Glucose Absorption by the Bioflavonoid Quercetin in the Obese and in Obese Type 2 Diabetics
Quercetin is a compound naturally found in various foods. It may have some role in the treatment of obesity and diabetes.
The purpose of this study is to investigate research volunteers with obesity or obesity with type 2 diabetes to determine whether quercetin affects the way glucose is absorbed by the body.
Read more
Thirty two participants aged 19 to 65 who are considered to be medically obese or obese with type 2 diabetes will be enrolled in this study. Before the onset of treatment, they will undergo a medical history, physical exam, blood work, and urinalysis. During the study, participants will be given an oral glucose tolerance test three times; during these tests they will receive 1 or 2 grams of quercetin, or placebo. Researchers will collect blood samples and analyze the effect of the treatment on blood glucose.
...
Read the detailed description
Postprandial hyperglycemia and the resultant hyperinsulinemia contribute to the cardiovascular complications seen in obesity and in type 2 diabetes. Epidemiological studies suggest that slow absorption of carbohydrates dampens glucose and insulin peaks, and reduces cardiovascular morbidity. The polyphenol quercetin is the most abundant flavanoid in plant-derived foods, and is sold as a dietary supplement. In vitro, quercetin is a potent and reversible inhibitor of glucose transport by the intestinal glucose transporter GLUT2. In vivo quercetin inhibits post absorptive glucose peaks in obese, diabetic rats. We hypothesize that quercetin blunts intestinal glucose absorption in humans, and attenuates postprandial hyperglycemia. We propose to test, in a double blind placebo controlled study, whether coadministration of 1 or 2 grams of quercetin with glucose will reduce plasma glucose concentrations during a 6 hour oral glucose tolerance test with 3 to 6 grams of 3-O-methyl glucose (3OMG) in non-diabetic obese subjects and in obese type 2 diabetic subjects. The glucose dose may be varied from 0 to 100 grams to better understand the competition between 3OMG and glucose. 3OMG is a non-metabolizable glucose analogue and is excreted unaltered in urine. 3OMG is not found in food and thus glucose absorption can be studies easily without the problem of a high baseline value. The use of 3OMG will provide a more accurate and true measures of glucose absorption. Study subjects will be 19 - 65 years with a body mass index greater than or equal to 30, without complications of diabetes, or on any medication other than oral hypoglycemic agents and aspirin. We will study 16 obese non diabetic subjects and 16 obese type 2 diabetics. Each subject will have 3 oral glucose tolerance tests, and will serve as his or her own control. We will compare the peak plasma glucose concentrations achieved during oral glucose tolerance tests and the area under the curve of plasma glucose to determine whether quercetin inhibits glucose absorption in humans. Such inhibition may partially explain the protective effects of plant derived foods on cardiovascular disease, and enable us to use quercetin or related compounds to dampen intestinal glucose absorption. We will also measure quercetin concentrations in the plasma, in circulating white blood cells and in urine to determine quercetin pharmacokinetics. Additionally, to determine the optimal 3OMG dose, we will study the absorption of glucose and 3OMG, without quercetin, in 12 non-diabetic obese subjects and 12 lean subjects to serve as controls.
- Being tested
- Quercetin, Placebo
- Keywords
- Hyperglycemia, Hyperinsulinemia, OGTT, GLUT2, Post-Prandial, Type 2 Diabetes, Obesity
- Medical subject headings
- Obesity, Diabetes Mellitus, Hyperglycemia, Hyperinsulinism, Diabetes Mellitus, Type 2
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
QuercetinOther
1 or 2 grams of quercetin or placebo will be given while patients undergo 6-hour OGTT
PlaceboOther
| Study group | Role | What they receive |
|---|---|---|
| 1 gram quercetin | Experimental | 1 gram quercetin with 6 hour OGTT Receives: Other: Quercetin |
| 2 grams quercetin | Experimental | 2 gram quercetin with 6 hour OGTT Receives: Other: Quercetin |
| placebo | Experimental | placebo with 6 hour OGTT Receives: Other: Placebo |
What is being measured
The primary outcome is the main question the study is designed to answer.
Does quercetin effect glucose absorption
Reduction in plasma glucose concentrations during 6-hour oral glucose tolerance test with 1 gram quercetin vs 2 grams quercetin vs placebo.
Measured: End of study
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted31 Jul 2003 (estimated)
- Study start30 Apr 2010
- Primary completion21 Dec 2015
- Study completion6 Aug 2021
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (3)Papers the sponsor has linked to this study.
- Other trials for ObesityStudies 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 2
- Primary purpose
- Basic science
- Allocation
- Non-randomised
- Intervention model
- Crossover
- Masking
- Triple blind
- Who is masked
- Participant, Care provider, Investigator
- Enrolment
- 24 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
- NCT00065676
- Sponsor's protocol ID
- 030256
- Other IDs
- 03-DK-0256
- Status last verified
- 22 Jan 2026
- First submitted
- 30 Jul 2003
- Last updated
- 5 Nov 2026
- Results posted
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
Publications
Mooradian AD, Thurman JE. Drug therapy of postprandial hyperglycaemia. Drugs. 1999 Jan;57(1):19-29. doi: 10.2165/00003495-199957010-00003.
PubMed 9951949Gavin JR 3rd. Pathophysiologic mechanisms of postprandial hyperglycemia. Am J Cardiol. 2001 Sep 20;88(6A):4H-8H. doi: 10.1016/s0002-9149(01)01830-6.
PubMed 11576519Yanovski SZ, Yanovski JA. Obesity. N Engl J Med. 2002 Feb 21;346(8):591-602. doi: 10.1056/NEJMra012586. No abstract available.
PubMed 11856799
Study at a glance
From the registry record, last updated by the sponsor on 5 Nov 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Inhibition of Intestinal Glucose Absorption by the Bioflavonoid Quercetin in the Obese and in Obese Type 2 Diabetics
- ClinicalTrials.gov ID
- NCT00065676
- Acronym / sponsor ID
- 030256
- Keywords
- Hyperglycemia, Hyperinsulinemia, OGTT, GLUT2, Post-Prandial, Type 2 Diabetes, Obesity
- Phase
- Phase 2
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 24 participants (actual)
- Lead sponsor
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)US National Institutes of Health
- Study start
- 30 Apr 2010 (actual)
- Primary completion
- 21 Dec 2015 (actual)
- Study completion
- 6 Aug 2021 (actual)
- First posted
- 31 Jul 2003 (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.
Quercetin is a compound naturally found in various foods. It may have some role in the treatment of obesity and diabetes.
The purpose of this study is to investigate research volunteers with obesity or obesity with type 2 diabetes to determine whether quercetin affects the way glucose is absorbed by the body.
Thirty two participants aged 19 to 65 who are considered to be medically obese or obese with type 2 diabetes will be enrolled in this study. Before the onset of treatment, they will undergo a medical history, physical exam, blood work, and urinalysis. During the study, participants will be given an oral glucose tolerance test three times; during these tests they will receive 1 or 2 grams of quercetin, or placebo. Researchers will collect blood samples and analyze the effect of the treatment on blood glucose.
...
Detailed description
Postprandial hyperglycemia and the resultant hyperinsulinemia contribute to the cardiovascular complications seen in obesity and in type 2 diabetes. Epidemiological studies suggest that slow absorption of carbohydrates dampens glucose and insulin peaks, and reduces cardiovascular morbidity. The polyphenol quercetin is the most abundant flavanoid in plant-derived foods, and is sold as a dietary supplement. In vitro, quercetin is a potent and reversible inhibitor of glucose transport by the intestinal glucose transporter GLUT2. In vivo quercetin inhibits post absorptive glucose peaks in obese, diabetic rats. We hypothesize that quercetin blunts intestinal glucose absorption in humans, and attenuates postprandial hyperglycemia. We propose to test, in a double blind placebo controlled study, whether coadministration of 1 or 2 grams of quercetin with glucose will reduce plasma glucose concentrations during a 6 hour oral glucose tolerance test with 3 to 6 grams of 3-O-methyl glucose (3OMG) in non-diabetic obese subjects and in obese type 2 diabetic subjects. The glucose dose may be varied from 0 to 100 grams to better understand the competition between 3OMG and glucose. 3OMG is a non-metabolizable glucose analogue and is excreted unaltered in urine. 3OMG is not found in food and thus glucose absorption can be studies easily without the problem of a high baseline value. The use of 3OMG will provide a more accurate and true measures of glucose absorption. Study subjects will be 19 - 65 years with a body mass index greater than or equal to 30, without complications of diabetes, or on any medication other than oral hypoglycemic agents and aspirin. We will study 16 obese non diabetic subjects and 16 obese type 2 diabetics. Each subject will have 3 oral glucose tolerance tests, and will serve as his or her own control. We will compare the peak plasma glucose concentrations achieved during oral glucose tolerance tests and the area under the curve of plasma glucose to determine whether quercetin inhibits glucose absorption in humans. Such inhibition may partially explain the protective effects of plant derived foods on cardiovascular disease, and enable us to use quercetin or related compounds to dampen intestinal glucose absorption. We will also measure quercetin concentrations in the plasma, in circulating white blood cells and in urine to determine quercetin pharmacokinetics. Additionally, to determine the optimal 3OMG dose, we will study the absorption of glucose and 3OMG, without quercetin, in 12 non-diabetic obese subjects and 12 lean subjects to serve as controls.
Study design
- Primary purpose
- Basic science
- Allocation
- Non-randomised
- Intervention model
- Crossover
- Masking
- Triple blind (participant, care provider, investigator)
- Number of arms
- 3
| Arm | Type | Receives |
|---|---|---|
| 1 gram quercetin | Experimental | Other: Quercetin1 gram quercetin with 6 hour OGTT |
| 2 grams quercetin | Experimental | Other: Quercetin2 gram quercetin with 6 hour OGTT |
| placebo | Experimental | Other: Placeboplacebo with 6 hour OGTT |
Who may qualify
- Ages
- 18 to 65 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (1 listed)
- Subjects to be recruited for the study will be male and female subjects between the ages of 18 and 65, able to give informed consent, with mild to moderate type 2 diabetes (such that fasting blood sugar <200mg/dl or HbA1C < 8.5), in otherwise good general health, with no other significant illnesses, blood pressure <=160/90 mmHg with or without medication, with no known severe target organ damage. End organ damage includes the following: proliferative retinopathy, serum creatinine >2, ischemic heart disease, congestive heart failure, known gastroparesis, peripheral vascular disease and severe peripheral neuropathy. Diabetic subjects must have a BMI greater than or equal to 30. Subjects will be taken off hypoglycemic agents for 3 to 7 days prior to each part of the study. This is to remove a confounding factor that may affect blood glucose concentrations attained during the OGTT, independent of the effect of quercetin. Whether these oral hypoglycemic agents have physiologically significant interaction with quercetin is not known. Severity of diabetes and biological duration of action of the drug will determine when to initiate this hold (from 3 to 7 days prior to OGTT). During the time that the subjects are off oral hypoglycemic agents, they will monitor their fasting blood glucose daily by glucometer. Therefore, for subjects with diabetes, only those subjects who self-monitor blood glucose are eligible for inclusion. If the fasting blood glucose in the morning exceeds 300 mg/dl, the subject will be withdrawn from the study and appropriate therapy resumed. Obese volunteers, with a BMI greater than or equal to 30, must be in good health, with no known illness. Healthy, normal weight subjects (BMI <25) will also be recruited as control subjects for the sampling study without querecetin. An upper age limit of 65 years was chosen to minimize renal toxicity of quercetin, as GFR declines with age and quercetin might produce mild though reversible renal impairment.
Key exclusion criteria (1 listed)
- Exclusion criteria will include the following: significant digestive abnormalities such as malabsorption or chronic diarrhea; significant organ malfunction including (but not limited to) liver disease, pulmonary disease, ischemic heart disease, heart failure, stroke, peripheral vascular disease, hypertension (BP >160/90), and anemia (hematocrit < 30); other serious or chronic illness; history of serious or chronic illness; any significant complications from diabetes such as kidney damage (renal insufficiency, serum creatinine >2), eye damage (proliferative retinopathy), severe diabetic neuropathy, coronary artery disease, or symptomatic peripheral vascular disease; smoking; alcohol or drug abuse; smokers; pregnancy (a urine pregnancy test will be performed on all women with reproductive age before each part of the study); lactation; positive HIV or hepatitis (B or C) screening tests (subjects will be notified of these test results). Diabetic subjects who choose not to self-monitor glucose daily by glucometer will be excluded.
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 |
|---|---|---|
| Quercetin1 or 2 grams of quercetin or placebo will be given while patients undergo 6-hour OGTT | Other | 1 gram quercetin, 2 grams quercetin |
| Placebo | Other | placebo |
Primary outcome
Does quercetin effect glucose absorption
Time frame: End of study
Reduction in plasma glucose concentrations during 6-hour oral glucose tolerance test with 1 gram quercetin vs 2 grams quercetin vs placebo.
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 5 Nov 2026.
- Background: PubMed 9951949Mooradian AD, Thurman JE. Drug therapy of postprandial hyperglycaemia. Drugs. 1999 Jan;57(1):19-29. doi: 10.2165/00003495-199957010-00003.
- Background: PubMed 11576519Gavin JR 3rd. Pathophysiologic mechanisms of postprandial hyperglycemia. Am J Cardiol. 2001 Sep 20;88(6A):4H-8H. doi: 10.1016/s0002-9149(01)01830-6.
- Background: PubMed 11856799Yanovski SZ, Yanovski JA. Obesity. N Engl J Med. 2002 Feb 21;346(8):591-602. doi: 10.1056/NEJMra012586. No abstract available.
- 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 2 study testing Quercetin in people with Obesity and Diabetes, 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 1 inclusion and 1 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 5 Nov 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 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.
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?
Does quercetin effect glucose absorption (time frame: End of study). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT00065676, which also lists 3 linked publications.
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 5 Nov 2026.