Vitamin D Deficiency in Obese Children an Its Relationship to Glucose Homeostasis

1. Vitamin D Deficiency in Obese Children an Its Relationship to Glucose Homeostasis Olson, M.L., et al J Clin Endocrinol Metab, 97, 279-285, 2012

2. Researchers 5.967 Impact Factor Internal Medicine Pediatric Endocrinology

3. Background • Obesity has tripled in U.S. children since 1980 • 19% of 6-19yr olds are obese • The rise in obesity has paralleled increases in childhood hypertension, hyperlipidemia, and Type 2 Diabetes. • Childhood obesity is associated with increase prevalence of cardiovascular events and Type 2 Diabetes in adulthood.

4. Supporting Evidence • Hypovitaminosis D in obese children and adolescents: relationship with adiposity, insulin sensitivity, ethnicity, and season • Metabolism 57:183-91 • Prevalence of vitamin D insufficiency in obese children and adolescents • J ClinEndocrinolMetab 92:2017-29

5. Study Objective • To compare prevalence of vitamin D deficiency in obese versus non-overweight children. • Examine relationships between: • Dietary habits and serum 25(OH)D levels • Abnormal glucose metabolism and obesity in children • Cross-sectional observational study- no intervention was implemented

6. Subjects • 411 obese and 89 non-overweight children (aged 6-16 years) residing in North Texas • Grouping based on BMI percentile-for-age: Obese= >95th percentile, non= <85th percentile • Adequate sample size, but could have included more non-overweight to better compare • Convenience sample of non-overweight subjects from Endocrinology Center for Hyperthyroidism • No known relationship between thyroid and vitamin D status • Same exclusion criteria for both groups • Meds: anticonvulsant, glucocorticoid, and/or vitamin D supplement • Health Status: Hepatic dz, renal dz, malabsorptive disorder, bone metabolism disorder, hypothalamic dz, genetic predisposition to obesity

7. Accounted for multiple subject characteristics Age BMI Gender Ethnicity Season Dietary practices

8. Calculating Pediatric BMI

9. Test Procedures • Used common, standard procedures determined to be reliable and valid: • Serum 25(OH)D • Diabetes Risk Factors (validated by Amer Diabetes Assoc) • OGTT • Fasting plasma glucose and insulin • HgbA1C • HOMA-IR (insulin resistance and beta-cell function) • All measurements taken in same way in both groups • Result evaluation based to gender, race, and season in both groups

10. Study Design- valid Used standardized, accurate measures of glucose metabolism and vitamin D status Included variety of subjects: different genders, races, ages Matched non-overweight subjects to obese based on age, race, and season  more accurate comparison

11. Relevant Outcomes • Obese had less seasonal variation in vitamin D status (p<0.03) • Breakfast skipping and high soda intakes were associated with lower vitamin D status (p<0.001) • When adjusted for age and BMI, vitamin D status negatively correlated with HOMA-IR and OGTT (p=0.001 and p=0.04) • Lower vitamin D status is associated with T2D risk factors in obese children

12. Author’s Conclusions • Study results show a negative relationship between vitamin D status and BMI in children • Glucose metabolism is related to vitamin D status • Limitation: unable to account for physical activity or sun-light exposure • Could aid in better understanding differences in vitamin D status between the 2 groups

13. Implications for Practice • Nutrition Professionals: • Raise awareness of dietary factors negatively affecting vitamin D status in children (breakfast skipping, soda consumption) • Highlight need for early dietary interventions • Clinical Professionals: • Suggests need for further study of vitamin D supplementation as a potential treatment for conditions such as insulin resistance