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Vitamin D, Glucose Control and Insulin Sensitivity in African-Americans

This study has been completed.
Sponsor:
ClinicalTrials.gov Identifier:
NCT00784511
First Posted: November 4, 2008
Last Update Posted: November 14, 2014
The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details.
Information provided by (Responsible Party):
Susan Harris, Tufts University
  Purpose
North American blacks tend to have low blood levels of vitamin D because pigmentation blocks vitamin D production in the skin. They also have higher rates of developing type 2 diabetes and higher rates of complications from the disease compared with whites. Although there is compelling evidence that adequate vitamin D may reduce the risk for type 2 diabetes in whites, recent evidence from a national survey demonstrated an association of vitamin D with diabetes in whites but not in blacks. However, the central hypothesis of this study is that providing enough supplemental vitamin D to blacks (raising their blood levels higher than that of most participants in the survey) will improve blood measures related to diabetes risk. The proposed study is a 12-week randomized, double-blind, placebo-controlled experiment designed to examine the effect of vitamin D supplementation (100 μg/d ) on insulin secretion, insulin sensitivity and glucose control in pre-diabetic black men and women aged 40 and older.

Condition Intervention Phase
Type 2 Diabetes Dietary Supplement: cholecalciferol Other: microcrystalline cellulose Phase 2

Study Type: Interventional
Study Design: Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)
Primary Purpose: Prevention
Official Title: Vitamin D, Glucose Control and Insulin Sensitivity in African-Americans

Resource links provided by NLM:


Further study details as provided by Susan Harris, Tufts University:

Primary Outcome Measures:
  • Insulin secretion rate [ Time Frame: 12 weeks ]
  • Insulin sensitivity index [ Time Frame: 12 weeks ]
  • 2-hr post load glucose [ Time Frame: 12 weeks ]

Enrollment: 100
Study Start Date: July 2008
Study Completion Date: February 2011
Primary Completion Date: February 2011 (Final data collection date for primary outcome measure)
Arms Assigned Interventions
Experimental: 1 vitamin D3
vitamin D3, 4000 IU/d
Dietary Supplement: cholecalciferol
4000 IU/d
Other Names:
  • vitamin D3
  • vitamin D
Placebo Comparator: 2
placebo
Other: microcrystalline cellulose
1/d
Other Name: placebo

  Eligibility

Information from the National Library of Medicine

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, Learn About Clinical Studies.


Ages Eligible for Study:   40 Years and older   (Adult, Senior)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes
Criteria

Inclusion Criteria:

  • African-American by self designation
  • Glucose intolerance defined as FPG ≥ 100 mg/dl or A1c ≥ 5.8%
  • BMI 25.0-39.9
  • Age 40 or older

Exclusion Criteria:

Medical Conditions

  • Diabetes potentially requiring pharmacotherapy, defined as A1c > 7%
  • Uncontrolled thyroid disease
  • Current parathyroid, liver or kidney disease
  • Renal stone within 5 years
  • Sarcoidosis, current pancreatitis, active tuberculosis, hemiplegia, gout
  • Inflammatory bowel disease, colostomy, malabsorption
  • Cancer other than basal cell skin cancer within 5 years
  • Uncontrolled arrhythmia in past year
  • Albinism or other condition associated with reduced skin pigmentation
  • Pregnancy over the last 1 year
  • Intent to become pregnant
  • Menopause onset within 1 year
  • Any other unstable medical condition Laboratory Tests
  • Fasting plasma glucose < 100
  • Hemoglobin A1c > 7%
  • Laboratory evidence of liver disease (e.g. AST > 70 U/L or ALT > 72 IU/L)
  • Laboratory evidence of kidney disease (e.g. estimated glomerular filtration rate < 60 ml/min/1.73 m2).
  • Elevated spot urine calcium to creatinine ratio > 0.38 mg/dl*
  • Abnormal serum calcium (serum calcium > 10.5 mg/dl)
  • Anemia (Hematocrit < 36% in men, <33% in women) Medications (use in past three months)
  • Estrogen or testosterone
  • Prescription vitamin D
  • Lithium
  • Oral corticosteroids
  • Anti-seizure medications
  • Unstable doses of psychotropics or phenothiazines
  • Cholestyramine Supplements (current use - may discontinue after screening)
  • Vitamin D supplements, cod liver oil, calcium supplements Other
  • Body mass index less <25 or > 39.9
  • Consumption of more than 14 alcoholic drinks per week
  • Inability to attend all three study visits as scheduled
  • Inability to provide written informed consent
  • age < 40 years
  • not African-American (by self-designation)
  • Participation in another research intervention study

    • corresponds to a 24-hour urinary calcium excretion > 400 mg
  Contacts and Locations
Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT00784511


Locations
United States, Massachusetts
Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University
Boston, Massachusetts, United States, 02111
Sponsors and Collaborators
Tufts University
  More Information

Responsible Party: Susan Harris, Scientist I, Tufts University
ClinicalTrials.gov Identifier: NCT00784511     History of Changes
Other Study ID Numbers: 8095
ADA 7-08-CR-27
First Submitted: November 3, 2008
First Posted: November 4, 2008
Last Update Posted: November 14, 2014
Last Verified: November 2014

Keywords provided by Susan Harris, Tufts University:
diabetes
vitamin D
African Americans
overweight
insulin sensitivity
glucose control

Additional relevant MeSH terms:
Hypersensitivity
Insulin Resistance
Immune System Diseases
Hyperinsulinism
Glucose Metabolism Disorders
Metabolic Diseases
Insulin
Vitamins
Vitamin D
Ergocalciferols
Cholecalciferol
Hypoglycemic Agents
Physiological Effects of Drugs
Micronutrients
Growth Substances
Bone Density Conservation Agents