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

NCT ID: NCT00784511

Last Updated: 2014-11-14

Basic Information

• Recruitment Status: COMPLETED
• Clinical Phase: PHASE2
• Total Enrollment: 100 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2008-07-31
• Study Completion Date: 2011-02-28

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.

Conditions

Type 2 Diabetes

Study Design

• Allocation Method: RANDOMIZED
• Intervention Model: PARALLEL
• Primary Study Purpose: PREVENTION
• Blinding Strategy: QUADRUPLE

Study Groups

1 vitamin D3

vitamin D3, 4000 IU/d

Group Type: EXPERIMENTAL

cholecalciferol

Intervention Type: DIETARY_SUPPLEMENT

4000 IU/d

2

placebo

Group Type: PLACEBO_COMPARATOR

microcrystalline cellulose

Intervention Type: OTHER

1/d

Interventions

cholecalciferol

4000 IU/d

Intervention Type: DIETARY_SUPPLEMENT

microcrystalline cellulose

1/d

Intervention Type: OTHER

Other Intervention Names

vitamin D3; vitamin D; placebo

Eligibility 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

• Minimum Eligible Age: 40 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: Yes

Sponsors

Tufts University

OTHER

Sponsor Role: lead

Responsible Party

Susan Harris

Scientist I

Responsibility Role: PRINCIPAL_INVESTIGATOR

Locations

Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University

Boston, Massachusetts, United States

Countries

United States

Other Identifiers

ADA 7-08-CR-27

Identifier Type: -

Identifier Source: secondary_id

8095

Identifier Type: -

Identifier Source: org_study_id