OLSON, M.L., ET AL Vitamin D Deficiency in Obese Children an Its Relationship to Glucose Homeostasis J Clin Endocrinol Metab, 97, , 2012

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

Subjects 411 obese and 89 non-overweight children (aged 6-16 years) residing in North Texas  Grouping based on BMI percentile-for-age: Obese= >95 th percentile, non= <85 th 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

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

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

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

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

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

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