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Protocol Details

Inhibition of Intestinal Glucose Absorption by the Bioflavonoid Quercetin in the Obese and in Obese Type 2 Diabetics

This study is NOT currently recruiting participants.

Summary | Eligibility | Citations | Contacts




Sponsoring Institute

National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)

Recruitment Detail

Type: Completed Study; data analyses ongoing
Gender: Male & Female
Min Age: 18
Max Age: 65

Referral Letter Required


Population Exclusion(s)




Recruitment Keyword(s)

Type 2 Diabetes;



Investigational Drug(s)


Investigational Device(s)



Other: Quercetin
Other: Placebo

Supporting Site

National Institute of Diabetes and Digestive and Kidney Diseases

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.

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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.


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.

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Mooradian AD, Thurman JE., Drug therapy of postprandial hyperglycaemia. Drugs. 1999 Jan;57(1):19-29.

Gavin JR 3rd. Pathophysiologic mechanisms of postprandial hyperglycemia. Am J Cardiol. 2001 Sep 20;88(6A):4H-8H.

Yanovski SZ, Yanovski JA. Obesity. N Engl J Med. 2002 Feb 21;346(8):591-602.

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Principal Investigator

Referral Contact

For more information:

Mark A. Levine, M.D.
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
(301) 402-5588

Irene T. Rozga, R.N.
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
National Institutes of Health
Building 10
Room 6C432B
10 Center Drive
Bethesda, Maryland 20892
(301) 496-1069

Office of Patient Recruitment
National Institutes of Health Clinical Center (CC)
Building 61, 10 Cloister Court
Bethesda, Maryland 20892
Toll Free: 1-800-411-1222
Local Phone: 301-451-4383
TTY: TTY Users Dial 7-1-1

Clinical Trials Number:


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