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Comparing Effects of 3 Sources of Garlic on Cholesterol Levels

This study has been completed.
Office of Dietary Supplements (ODS)
Information provided by:
National Center for Complementary and Integrative Health (NCCIH) Identifier:
First received: March 14, 2003
Last updated: August 16, 2006
Last verified: August 2006
The purpose of this study is to determine whether fresh garlic can positively affect cholesterol in adults with moderately high cholesterol levels. This study will also determine whether the same effects can be found for two main types of garlic supplements: a dried powdered garlic (designed to yield the same effect as fresh garlic) and an aged garlic extract preparation.

Condition Intervention Phase
Drug: Fresh garlic or garlic supplements
Phase 2
Phase 3

Study Type: Interventional
Study Design: Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Double-Blind
Primary Purpose: Treatment
Official Title: Comparing Effects of 3 Sources of Garlic on Serum Lipids

Resource links provided by NLM:

Further study details as provided by National Center for Complementary and Integrative Health (NCCIH):

Primary Outcome Measures:
  • LDL-cholesterol; measured at baseline, once a month, and post-intervention

Secondary Outcome Measures:
  • HDL-cholesterol; measured at baseline, once a month, and post-intervention
  • Triacylglycerols; measured at baseline, once a month, and post-intervention
  • Blood pressure; measured at baseline, once a month, and post-intervention
  • Platelet aggregation; measured at baseline, once a month, and post-intervention

Estimated Enrollment: 220
Study Start Date: May 2002
Estimated Study Completion Date: April 2005
Detailed Description:

Garlic supplements are the most consumed herbal products in the United States. The most common health claim made for garlic supplements is cholesterol lowering activity. This claim has not been supported by recent clinical trials and meta-analyses. However, data suggest that it is not necessarily the garlic that has been ineffective, but rather the particular garlic preparations being used. To date, the predominant type of garlic preparation used in these clinical trials has been dried garlic powders. A few clinical trials have reported beneficial lipid effects using an aged garlic extract, and only a small number of inconclusive uncontrolled trials have used fresh garlic. A rigorous trial directly comparing different types of garlic preparations for their effects on serum lipids is needed.

Adults with moderately elevated low density lipoprotein cholesterol (LDL-C) will be randomized to one of four groups for 6 months: fresh garlic, dried powdered garlic tablets, aged garlic extract tablets, or placebo control. The fresh garlic will be provided to patients with "study sandwiches"; all other groups will receive the same study sandwiches without the garlic. All patients will take daily study tablets, but the tablet assignment will be double-blind. Patients will pick up study sandwiches twice a week and study tablets once every 2 weeks for 28 weeks. Blood samples will be taken once a month, with additional blood draws at the start and end of the study.


Ages Eligible for Study:   30 Years to 65 Years   (Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes

Inclusion Criteria:

  • LDL-C 130-190 mg/dL (fasting single sample)
  • BMI (body mass index) 19-30 kg/m2 (42-66 lb/m2)
  • Weight stable for last 2 months
  • Not actively on a weight loss plan
  • Ethnicity representative of local population
  • No plans to move from the area over the next 9 months

Exclusion Criteria:

  • Pregnant, lactating, within 6 months postpartum, or planning to become pregnant in the next year
  • Diabetes (type I or II) or history of gestational diabetes
  • Heart disease
  • Active neoplasms
  • Renal or liver disease
  • Hyperthyroidism or hypothyroidism
  • Lipid lowering medications (known to affect lipid metabolism, platelet function, or antioxidant status)
  • Blood pressure medications
  • Excessive alcohol intake (self reported, more than 3 drinks/day)
  • Currently under psychiatric care or severely clinically depressed
  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: NCT00056511

United States, California
Stanford Center for Research in Disease Prevention
Palo Alto, California, United States, 94304-1583
Sponsors and Collaborators
National Center for Complementary and Integrative Health (NCCIH)
Office of Dietary Supplements (ODS)
Principal Investigator: Christopher D. Gardner, Ph.D. Stanford Center for Research in Disease Prevention
  More Information

Publications automatically indexed to this study by Identifier (NCT Number): Identifier: NCT00056511     History of Changes
Other Study ID Numbers: R01AT001108-01 ( US NIH Grant/Contract Award Number )
Study First Received: March 14, 2003
Last Updated: August 16, 2006

Keywords provided by National Center for Complementary and Integrative Health (NCCIH):
Randomized Clinical Trial

Additional relevant MeSH terms:
Lipid Metabolism Disorders
Metabolic Diseases processed this record on May 24, 2017