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Boston, Massachusetts 02111


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.


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



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Boston, Massachusetts 02111
United States

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Site Status: N/A

Data Source: ClinicalTrials.gov

Date Processed: October 09, 2019

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