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Effects of Purple Vegetables on Cardiovascular Disease (CVD) Risk Factors

This study is currently recruiting participants. (see Contacts and Locations)
Verified June 2013 by University of Guelph
Ontario Ministry of Agriculture, Food and Rural Affairs
Information provided by (Responsible Party):
Kelly Anne Meckling, PhD, University of Guelph Identifier:
First received: March 22, 2012
Last updated: June 12, 2013
Last verified: June 2013

The hypothesis is that richly coloured purple vegetables, rich in polyphenolic compounds including anthocyanins will have higher antioxidant and other biological activities, than more lightly coloured versions of these foods. Diets of human subjects will be modified to allow consumption of 200-300 g of raw carrots or cooked potatoes. Participants will be randomized to consume either orange or purple carrots, or white or purple potatoes. They will consume these diets for 12 weeks and bioavailability of polyphenolics will be examined as well as anthropometry and blood biochemistry for changes in risk factors associated with cardiovascular disease.

Condition Intervention Phase
Type II Diabetes
Other: vegetable
Phase 1

Study Type: Interventional
Study Design: Allocation: Randomized
Endpoint Classification: Efficacy Study
Intervention Model: Parallel Assignment
Masking: Open Label
Primary Purpose: Prevention
Official Title: A Pilot Study of the Effects of Replacing Orange Carrots and White Potatoes With Purple Varieties, on Risk Factors for Cardiovascular Disease

Resource links provided by NLM:

Further study details as provided by University of Guelph:

Primary Outcome Measures:
  • Blood cholesterol [ Time Frame: 12 weeks ] [ Designated as safety issue: No ]
    blood will be collected at baseline before the experimental foods are introduced and again 6 weeks into the intervention period and during the last week of the intervention (week 12)

Secondary Outcome Measures:
  • blood pressure [ Time Frame: 12 weeks ] [ Designated as safety issue: No ]
    Participants will have their body weight and blood pressure taken at weekly counselling sessions

  • body composition [ Time Frame: 12 weeks ] [ Designated as safety issue: No ]
    body composition will be measured in well hydrated subjects using bioelectric impedence analysis

  • insulin resistance [ Time Frame: 12 weeks ] [ Designated as safety issue: No ]
    insulin resistance will be measured by way of an oral glucose tolerance test and collection of venous blood samples for the subsequent 3 hours on two occasions, baseline and during the last week of the intervention diet.

  • blood and urinary polyphenol metabolites [ Time Frame: 12 weeks ] [ Designated as safety issue: No ]

    venous blood and urine will be collected to determine the metabolic profiles of polyphenolics in individual participants.

    Based on intake data, the bioavailability of the polyphenols in the foods will be estimated.

  • circulating biomarkers of cardiovascular disease and type II diabetes risk [ Time Frame: 12 weeks ] [ Designated as safety issue: No ]
    Blood will be collected for measurement of multiple cytokines, growth factors and other blood biomarkers associated with these diseases.

Estimated Enrollment: 60
Study Start Date: April 2012
Estimated Study Completion Date: December 2014
Estimated Primary Completion Date: December 2014 (Final data collection date for primary outcome measure)
Arms Assigned Interventions
Placebo Comparator: White potato
Participants will consume 300-500 g of cooked white potatoes per day
Other: vegetable
200-300 g raw carrots or 300-500 g cooked potatoes
Experimental: Purple Potato
Participants will consume 300-500 g of cooked purple potato per day
Other: vegetable
200-300 g raw carrots or 300-500 g cooked potatoes
Placebo Comparator: Orange carrots
Participants will consume 200-300 g typical varieties of orange carrots during the intervention
Other: vegetable
200-300 g raw carrots or 300-500 g cooked potatoes
Experimental: Purple Carrots
Participants will consume 200-300 g raw purple carrots instead of orange carrots in the control arm
Other: vegetable
200-300 g raw carrots or 300-500 g cooked potatoes


Ages Eligible for Study:   18 Years to 65 Years
Genders Eligible for Study:   Both
Accepts Healthy Volunteers:   No

Inclusion Criteria:

  • adult men and women 18-65 years of age
  • must have a least one of the following risk factors associated with increased risk of type II diabetes and/or cardiovascular disease:

    • borderline high or hypertension or undergoing treatment for such
    • abnormal fasting blood glucose or undergoing treatment for such
    • overweight or obese
    • borderline high or high LDL-cholesterol or undergoing treatment for such
    • borderline low or low HDL-cholesterol
    • borderline high or high triglycerides or undergoing treatment for such

Exclusion Criteria:

  • smokers, pregnant or nursing women
  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: NCT01564498

Contact: Kelly A Meckling, PhD 5198244120 ext 53742
Contact: Saqib Mannan, BSc 5198244120 ext 53728

Canada, Ontario
Human Nutraceutical Research Unit Recruiting
Guelph, Ontario, Canada, N1G2W1
Contact: Amanda J Wright, PhD    5198244120 ext 54697   
Contact: Amy Tucker, PhD    5198244120 ext 53925      
Principal Investigator: Kelly A Meckling, PhD         
Sub-Investigator: Saqib Mannan, BSc         
Sub-Investigator: Ricky Janssen, BSc         
Sponsors and Collaborators
University of Guelph
Ontario Ministry of Agriculture, Food and Rural Affairs
  More Information

No publications provided

Responsible Party: Kelly Anne Meckling, PhD, Professor, University of Guelph Identifier: NCT01564498     History of Changes
Other Study ID Numbers: 2012MeckPurpleVeg
Study First Received: March 22, 2012
Last Updated: June 12, 2013
Health Authority: Canada: Health Canada

Keywords provided by University of Guelph:
insulin sensitivity
glucose tolerance
metabolic syndrome

Additional relevant MeSH terms:
Cardiovascular Diseases
Diabetes Mellitus, Type 2
Diabetes Mellitus
Endocrine System Diseases
Glucose Metabolism Disorders
Lipid Metabolism Disorders
Metabolic Diseases
Pathologic Processes
Vascular Diseases processed this record on November 20, 2014