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The Effect of Purple Sweet Potato (PSP)-Juice on Liver Enzymes and Blood Pressure

This study has been completed.
Yakult Honsha Co., LTD
Information provided by:
TNO Identifier:
First received: August 18, 2009
Last updated: April 13, 2010
Last verified: April 2010

Purple Sweet Potato juice (PSP-juice) is a juice based on purple-fleshed sweet potato concentrate, containing a high level of anthocyanins. Purple-fleshed sweet potatoes have attracted attention to industry and scientists due to multiple physiological functions such as radical-scavenging, ACE-inhibitory and α-glucosidase inhibitory activities in vitro, and also hepato-protective, antihypertensive and antihyperglycemic effects in vivo. Previous studies in Japanese subjects showed potential beneficial effects of PSP beverages on liver function and blood pressure in volunteers with impaired hepatic function and/or hypertension.

The main objective of this study is to examine the effect of PSP-juice on liver enzymes and blood pressure. The secondary objective is to examine the effects of PSP-juice juice on insulin resistance.

Condition Intervention
Health Blood Pressure Liver Function Insulin Resistance Dietary Supplement: purple sweet potato (PSP)-juice

Study Type: Interventional
Study Design: Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Double Blind (Participant, Care Provider, Investigator, Outcomes Assessor)
Primary Purpose: Treatment
Official Title: The Effect of Purple Sweet Potato (PSP)-Juice on Liver Enzymes and Blood Pressure

Resource links provided by NLM:

Further study details as provided by TNO:

Primary Outcome Measures:
  • liver enzymes [ Time Frame: every 2 weeks during 8-weeks intervention ]

Secondary Outcome Measures:
  • blood pressure [ Time Frame: every 2 weeks during 8-weeks intervention ]
  • insulin resistance [ Time Frame: every 2 weeks during 8-weeks intervention ]

Enrollment: 40
Study Start Date: June 2009
Study Completion Date: December 2009
Primary Completion Date: December 2009 (Final data collection date for primary outcome measure)
Arms Assigned Interventions
Experimental: purple sweet potato juice
Daily oral intake of 3x 125 ml of PSP-juice for a period of 8 weeks
Dietary Supplement: purple sweet potato (PSP)-juice
Daily oral intake of 3x 125 ml of PSP-juice or control juice
Placebo Comparator: Control juice
Daily oral intake of 3x 125 ml of control juice for a period of 8 weeks
Dietary Supplement: purple sweet potato (PSP)-juice
Daily oral intake of 3x 125 ml of PSP-juice or control juice

Detailed Description:

Study design: The study is designed as a randomized, parallel, placebo-controlled, double-blind study.

Study population: 40 healthy adult female and/or male subjects, 40-70 yr old with a BMI 25-35 kg/m2, mildly elevated serum liver enzymes, and high normal blood pressure or mild hypertension.

Intervention: Daily oral intake of 3x 125 ml of PSP-juice or control juice for a period of 8 weeks.

Main study parameters/endpoints: Liver enzymes (GGT, ALAT, ASAT), blood pressure, glucose, insulin, haematology and serum clinical chemical profile


Ages Eligible for Study:   40 Years to 70 Years   (Adult, Senior)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes

Inclusion Criteria:

  • Healthy as assessed by the: Health and Lifestyle Questionnaire, results of the pre study laboratory tests in blood
  • Males/Females aged 40-70 years (boundaries included) at Day 01 of the study
  • Body Mass Index (BMI) 25-35 (boundaries included) kg/m2
  • Liver enzymes above reference values GGT ≥ 45 IU/L (for males) and ≥ 35 IU/L (for females), and/or ASAT ≥ 45 IU/L (for males and females), and/or ALAT ≥ 50 IU/L (for males) and ≥ 40 IU/L (for females)
  • Blood pressure (automated measurements at site): systolic blood pressure 130-159 mm Hg (boundaries included) and/or diastolic blood pressure 85-99 mm Hg (boundaries included)
  • Voluntary participation
  • Having given written informed consent
  • Willing to comply with the study procedures
  • Willing to give up blood/plasma donation during the study
  • Willing to accept use of all nameless data, including publication, and the confidential use and storage of all data for at least 15 years
  • Willing to accept the disclosure of the financial benefit of participation in the study to the authorities concerned.

Exclusion Criteria:

  • Participation in any clinical trial including blood sampling and/or administration of substances up to 90 days before Day 01 of this study
  • Participation in any non-invasive clinical trial up to 30 days before Day 01 of this study, including no blood sampling and/or oral, intravenous, inhalatory administration of substances
  • Having a history of medical or surgical events that may significantly affect the study outcome
  • Any concomitant medication, with the exception of occasional use of a paracetamol tablet, that may influence the outcome of the study (to be judged by the medical investigator)
  • Food allergy/intolerance
  • Alcohol consumption > 28 units/week for males and > 21 units/week for females
  • Smoking > 10 cigarettes per day
  • Reported unexplained weight loss or gain of > 2 kg in the month prior to the pre study screening
  • Reported slimming or medically prescribed diet
  • Participation in night shift work
  • Pregnant or lactating or wishing to become pregnant in the period of the study
  • Personnel of TNO Quality of Life, their partner and their first and second degree relatives
  • Not having a general practitioner
  • Not willing to accept information-transfer concerning participation in the study, or information regarding his/her health, like laboratory results, findings at anamnesis or physical examination and eventual adverse events to and from his general practitioner.
  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: NCT00962195

TNO Quality of Life
Zeist, Utrecht, Netherlands
Sponsors and Collaborators
Yakult Honsha Co., LTD
Principal Investigator: Esther Boelsma, PhD TNO
Study Director: Ineke Klopping-Ketelaars, PhD TNO
  More Information

Responsible Party: E. Boelsma, PhD, TNO Quality of Life, Business unit biosciences Identifier: NCT00962195     History of Changes
Other Study ID Numbers: P8604
Study First Received: August 18, 2009
Last Updated: April 13, 2010

Keywords provided by TNO:
blood pressure
liver enzymes
insulin resistance

Additional relevant MeSH terms:
Insulin Resistance
Glucose Metabolism Disorders
Metabolic Diseases processed this record on June 22, 2017