Allicin Bioavailability From Garlic Supplements and Garlic Foods

The recruitment status of this study is unknown because the information has not been verified recently.
Verified November 2009 by Silliker, Inc..
Recruitment status was  Active, not recruiting
Information provided by:
Silliker, Inc. Identifier:
First received: April 1, 2009
Last updated: November 18, 2009
Last verified: November 2009

April 1, 2009
November 18, 2009
April 2009
April 2011   (final data collection date for primary outcome measure)
Breath allyl methyl sulfide [ Time Frame: 1-32 hours ] [ Designated as safety issue: No ]
Same as current
Complete list of historical versions of study NCT00874666 on Archive Site
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Allicin Bioavailability From Garlic Supplements and Garlic Foods
Allicin Bioavailability of Garlic Products

This study will measure the bioavailability of allicin, the main active compound of garlic, from garlic supplements and garlic foods (raw, cooked, processed) so that

  • supplement manufacturers and clinical investigators know how supplements need to be made and consumed to obtain high bioavailability
  • consumers can know how garlic can be prepared to obtain any established health benefits of garlic.

The bioavailability of allicin, the main active compound of garlic, from garlic supplements and garlic foods is highly questionable and unpredictable from in vitro tests, due to dependence upon alliinase activity under conditions that challenge alliinase activity (heat, gastric acid, intestinal proteases). It is likely that garlic supplement manufacturing procedures and coatings, meal conditions when supplements are consumed (high or low protein), and garlic food preparation conditions (temperature, surface area) will greatly affect allicin bioavailability. Such variability may account for some of the many conflicts seen in clinical trials on cardiovascular disease risk factors.

To resolve these issues, this study will determine the actual bioavailability of allicin from several types of garlic supplements and garlic foods under various conditions. Bioavailability will be determined by measuring the area under the 32-hour curve for breath concentrations of allyl methyl sulfide, the main metabolite allicin.

Phase 0
Allocation: Non-Randomized
Endpoint Classification: Bio-availability Study
Intervention Model: Crossover Assignment
Masking: Open Label
Primary Purpose: Basic Science
  • Other: crushed garlic clove
    1 gram crushed garlic in gelatin capsules, one dose once every 2-16 weeks
    Other Name: Allium sativum
  • Dietary Supplement: garlic powder tablet
    tablets, dose to contain 1 gram of garlic powder, consume one dose once every two weeks for up to 52 weeks
    Other Name: Kwai, Garlique
  • Active Comparator: 1
    Positive control with 100% allicin bioavailability
    Intervention: Other: crushed garlic clove
  • Experimental: 2
    garlic powder tablet
    Intervention: Dietary Supplement: garlic powder tablet
Not Provided

*   Includes publications given by the data provider as well as publications identified by Identifier (NCT Number) in Medline.
Active, not recruiting
April 2011
April 2011   (final data collection date for primary outcome measure)

Inclusion Criteria:

  • in good health (self-judged)
  • BMI (body mass index): 19-32 kg/m2
  • not planning to move out of the area in the next year
  • willing to abstain from consuming garlic and onion and foods that contain them for two days prior to and during each test (diet restrictions)
  • able to deliver bags of breath to the research facility five times in two days
  • willing to eat whole wheat tuna sandwiches

Exclusion Criteria:

  • known serious health problems: diabetes, heart disease, active neoplasms, renal or liver disease, hyper- or hypothyroidism, breathing disorders, gastroesophageal reflux disease (GERD), gastrointestinal disease (absorption interference)
  • known allergy to garlic or wheat
  • tobacco user
  • excessive alcohol intake (³2 drinks/day, self-reported)
  • unable to speak English well
18 Years to 72 Years
Contact information is only displayed when the study is recruiting subjects
United States
R21 AT004236, R21AT004236, 1R21 AT004236-01
Larry D. Lawson, principal investigator, Silliker, Inc.
Silliker, Inc.
National Center for Complementary and Integrative Health (NCCIH)
Principal Investigator: Larry D Lawson, Ph. D. Silliker, Inc.
Silliker, Inc.
November 2009

ICMJE     Data element required by the International Committee of Medical Journal Editors and the World Health Organization ICTRP