The purpose of the study is to evaluate the change in insulin sensitivity and secretion indices (early markers for development of diabetes) after 4 weeks of a megadose of Vitamin D. This will also help to calculate sample size for and choose an appropriate index for a larger randomized control trial which may be required subsequently.

Accumulating evidence suggests that serum Vitamin D levels may be inversely related to the prevalence of diabetes, to the concentration of glucose , insulin resistance and metabolic syndrome.The available trials have been conducted using small sample sizes in different subgroups (hemodialyzed patients , healthy volunteers , gestational diabetes and post menopausal women ) document variable results with a positive result in some (hemodialysis and gestational diabetes) and no effect in other settings(healthy volunteers and postmenopausal women).We therefore, planned this trial to study the effect of vitamin D supplementation (240,000 IU) on insulin secretion and peripheral insulin sensitivity.This will also help to calculate sample size for and choose an appropriate index for a larger randomized control trial which may be required subsequently.

Study design and comparison:Single group, open label intervention trial involving assessment of insulin sensitivity and secretion in 30 volunteers before and after 4weeks of a megadose of Vitamin D. The pre and post intervention results will be compared using the paired t test.

Inclusion Criteria:

• Male
• ≥30 years of age
• Waist circumference ≥80 cm

Exclusion Criteria:

• Diabetic- Fasting Blood Sugar >126 mg/dl or on anti-diabetic medication
• BP>140/90 or on anti-hypertensive medication
• Receiving Vitamin D or calcium supplementation
• Chronic disease-renal/hepatic/malignancy/gastrointestinal
• On any medication within the last one month which could potentially influence insulin secretion, insulin sensitivity, Vitamin D or Calcium metabolism
• Febrile illness or infective morbidity in the past 10 days