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

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. Identifier: NCT00784511
Recruitment Status : Completed
First Posted : November 4, 2008
Last Update Posted : November 14, 2014
Information provided by (Responsible Party):
Susan Harris, Tufts University

Brief Summary:
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 or disease Intervention/treatment Phase
Type 2 Diabetes Dietary Supplement: cholecalciferol Other: microcrystalline cellulose Phase 2

Study Type : Interventional  (Clinical Trial)
Actual Enrollment : 100 participants
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
Study Start Date : July 2008
Actual Primary Completion Date : February 2011
Actual Study Completion Date : February 2011

Resource links provided by the National Library of Medicine

U.S. FDA Resources

Arm Intervention/treatment
Experimental: 1 vitamin D3
vitamin D3, 4000 IU/d
Dietary Supplement: cholecalciferol
4000 IU/d
Other Names:
  • vitamin D3
  • vitamin D
Placebo Comparator: 2
Other: microcrystalline cellulose
Other Name: placebo

Primary Outcome Measures :
  1. Insulin secretion rate [ Time Frame: 12 weeks ]
  2. Insulin sensitivity index [ Time Frame: 12 weeks ]
  3. 2-hr post load glucose [ Time Frame: 12 weeks ]

Information from the National Library of Medicine

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

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

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 identifier (NCT number): NCT00784511

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

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

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

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