Childhood obesity is a rapidly growing epidemic in the US and the world. Current estimates
suggest that 30% of our nation's children are either overweight ot obese. Obesity is a major
risk factor towards the development of insulin resistance, which, in turn is a major risk
factor for the development of type 2 diabetes. Prior research has suggested that vitamin D
therapy may be a safe, inexpensive, and effective method of reducing insulin resistance and
a person's risk of developing diabetes.
The investigators' prior studies have shown that daily 4,000 IU vitamin D therapy is a safe
and effective method of improving insulin resistance based on a calculation called the
The next step in identifying whether vitamin D truly improves insulin resistance is to use
oral glucose tolerance testing (OGTT), which is a better real-life measure of insulin
resistance compared to the previously used HOMA-IR.
The investigators intend to recruit 20 obese adolescent subjects from the PI's obesity
clinic to participate in the study. Investigators expect 5 to drop out, therefore leaving 15
subjects to complete the study. Eligible and assenting subjects (with consent from a parent)
will be admitting to the Pediatric Procedure Suite and MU Women's and Children's Hospital.
They will have an IV placed in the arm by a nurse experienced with working with children.
The subjects will have blood drawn from the IV checking for vitamin D level, insulin,
glucose, and c-peptide level (another marker for insulin status). The subject will then be
asked to drink a 75 gram glucose solution. Additional blood will be drawn from the IV site
to check for glucose, insulin, and c-peptide levels at 30 minutes, 60 minutes, 90 minutes,
and 120 minutes. A total of 30 mL (2 tablespoons) of blood will be drawn that day. The
subject will have the IV removed and will be discharged to then take two 2,000 IU vitamin D3
pills (total 4,000 IU) daily for six months.
At a routine 3 months clinical visit, the subject will be tested for routine, standard of
care, basic metabolic profile (BMP) with 4 ml of blood (less than 1 teaspoon) to assess for
high calcium levels, a potential complication of vitamin D therapy. In the investigators'
previous study of adolescents taking 4,000 IU vitamin D daily for six months, no subject
developed a high calcium level.
At six months, the subject will return to the Pediatric procedure suite to have another OGTT
and labs via IV as described above.
- Obese adolescent (BMI >85th percentile for age)
- 9-19 years of age
- attending the ADOBE clinic at the University of Missouri
- 25OH vitamin D level within past 3 months
- use of vit D supplements other than standard multi-vitamin preparation (i.e., should
not be receiving vit D > 1000 IU/d)
- use of medications that interfere with vit D metabolism (e.g., anti-convulsive)
- history of hepatic or renal disorders, hypercalciuria, or hypercalcemia
- undergoing UV radiation as medical therapy
- pregnancy; cigarette smoking; current use of a tanning bed
- current type 2 diabetes
- any current antihyperglycemic medication use (e.g. metformin, insulin) less than one
month prior to initial OGTT.