Effects of Green Tea on Level of Serum Uric Acid in Healthy Individuals

Green tea has been extensively investigated for several potential health benefits. Previous studies have suggested that green tea may lower serum uric acid level in human. The purpose of this study is to investigate uric-lowering properties of green tea in healthy individuals.

Study Overview

• Status: Completed
• Conditions: Hyperuricemia; Gout
• Intervention / Treatment: Dietary supplement: green tea extracts 2 gm/day; Dietary supplement: green tea extracts 4 gm/day; Dietary supplement: green tea extracts 6 gm/day

Detailed Description

Elevated serum uric acid is related to the risk of development of gout, the most common inflammatory arthritis in men. Allopurinol, a xanthine oxidase inhibitor, is one of the uric-lowering agents commonly used in patients suffering from recurrent and chronic gout. Nevertheless, its use is limited by adverse effects and serious allergic reaction in some patients.

Green tea is one of the most frequently consumed beverages, particularly in Japan. Green tea contains high level of catechins, in which Epigallocatechin gallate (EGCG) is the most abundant compound among other types of catechins. Antioxidant effect contributes to various potential health benefits of green tea. Several in-vitro studies have found that green tea inhibits xanthine oxidase activity and subsequently decreases reactive oxygen species (ROS) and uric acid production. We therefore would like to investigate the hypouricemic effects of green tea.

The study consists of three periods with a total duration of four weeks. The first week is the control period. The following two weeks is the interventional period and the last week is the follow up period. Thirty healthy participants will be randomly assigned into three experimental groups, receiving 2 gm/day, 4 gm/day and 6 gm/day (in capsule, two times after meal) of green tea extract during interventional period. Blood and urine samples will be taken at the beginning and at the end of each study period.

• Study Type: Interventional
• Enrollment (Actual): 30
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Thailand
  • Chiang Mai, Thailand, 50200
    • Department of Internal Medicine, Faculty of Medicine, Chiang Mai University

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• Age 18 years or older
• Healthy individuals
• Normal renal and liver function from blood tests

Exclusion Criteria:

• Presence of co-morbidity or currently ill
• Currently using any medication or nutritional supplement product that may affect serum uric acid level
• Serum creatinine higher than 1.5 mg/dl
• Abnormal serum Aspartate aminotransferase (AST) and/or Alanine transaminase (ALT)
• Greater than 15% change in serum uric acid during control period

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Green tea extracts 2 gm/day; Green tea extracts 2 gm/day for 14 days	Dietary supplement: green tea extracts 2 gm/day; Green tea extracts capsule (1 gm per capsule), taken after meal, twice daily for 14 days. Total dosage is 2 grams per day.
Experimental: Green tea extracts 4 gm/day; Green tea extracts 4 gm/day for 14 days	Dietary supplement: green tea extracts 4 gm/day; Green tea extracts capsule (1 gm per capsule), taken after meal, twice daily for 14 days. Total dosage is 4 grams per day.
Experimental: Green tea extracts 6 gm/day; Green tea extracts 6 gm/day for 14 days	Dietary supplement: green tea extracts 6 gm/day; Green tea extracts capsule (1 gm per capsule), taken after meal, twice daily for 14 days. Total dosage is 6 grams per day.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
serum uric acid	4 weeks (prior to, immediately after and 7 days after intervention)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
urinary uric acid excretion		4 weeks (prior to, immediately after and 7 days after intervention)
serum antioxidant activity		4 weeks (prior to, immediately after and 7 days after intervention)
serum EGCG level	Measurements of serum level of epigallocatechin gallate (EGCG)	1 week (immediately after and 7 days after intervention)
Adverse events	Adverse events during 4-week study	4 week (prior to, immediately after and 7 days after intervention)

Collaborators and Investigators

• Sponsor: Chiang Mai University
• Investigators: Principal Investigator: Kanon Jatuworapruk, M.D, Department of Internal medicine, Faculty of Medicine, Chiang Mai University, Thailand

Study record dates

Study Major Dates

• Study Start: June 1, 2011
• Primary Completion (Actual): September 1, 2012
• Study Completion (Actual): March 1, 2013

Study Registration Dates

• First Submitted: May 31, 2011
• First Submitted That Met QC Criteria: May 31, 2011
• First Posted (Estimate): June 2, 2011

Study Record Updates

• Last Update Posted (Estimate): April 25, 2013
• Last Update Submitted That Met QC Criteria: April 23, 2013
• Last Verified: April 1, 2013

More Information

Terms related to this study

• Keywords: uric acid; gout; antioxidant; hyperuricemia; xanthine oxidase inhibitor; green tea; catechins
• Additional Relevant MeSH Terms: Pathologic Processes; Hyperuricemia
• Other Study ID Numbers: MED-11-02-07-13-X

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No