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

Type 2 Diabetes Clinical Trial

Official title:

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

Clinical Trial Details — Status: Completed

Administrative data

• NCT number: NCT00784511
• Other study ID #: 8095
• Secondary ID: ADA 7-08-CR-27
• Status: Completed
• Phase: Phase 2
• First received: November 3, 2008
• Last updated: November 13, 2014
• Start date: July 2008
• Est. completion date: February 2011

Study information

• Verified date: November 2014
• Source: Tufts University
• Contact: n/a
• Is FDA regulated: No
• Health authority: United States: Institutional Review Board
• Study type: Interventional

Clinical Trial 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.

Recruitment information / eligibility

• Status: Completed
• Enrollment: 100
• Est. completion date: February 2011
• Est. primary completion date: February 2011
• Accepts healthy volunteers: Accepts Healthy Volunteers
• Gender: Both
• Age group: 40 Years and older

Eligibility

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

Study Design

Allocation: Randomized, Endpoint Classification: Efficacy Study, Intervention Model: Parallel Assignment, Masking: Double Blind (Subject, Caregiver, Investigator, Outcomes Assessor), Primary Purpose: Prevention

Related Conditions & MeSH terms

• Insulin Resistance
• Type 2 Diabetes

Intervention

Dietary Supplement:
• cholecalciferol
4000 IU/d

Other:
• microcrystalline cellulose
1/d

Locations

Country	Name	City	State
United States	Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University	Boston	Massachusetts

Sponsors (1)

Lead Sponsor	Collaborator
Tufts University

Country where clinical trial is conducted

United States, 

Outcome

Type	Measure	Description	Time frame	Safety issue
Primary	Insulin secretion rate		12 weeks	No
Primary	Insulin sensitivity index		12 weeks	No
Primary	2-hr post load glucose		12 weeks	No