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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. Researchers. 5.967 Impact Factor Internal Medicine Pediatric Endocrinology. Background. Obesity has tripled in U.S. children since 1980
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Vitamin D Deficiency in Obese Children an Its Relationship to Glucose Homeostasis Olson, M.L., et al J ClinEndocrinolMetab, 97, 279-285, 2012
Researchers • 5.967 Impact Factor • Internal Medicine • Pediatric Endocrinology
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.
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
Objectives • The aim of this study was to examine the relationship between dietary habits and 25(OH)D status in obese children. • Examine the relationship between 25(OH)D and glucose homeostasis. • Cross-sectional observational study
Selection of Subjects • 411 obese children (BMI >95th percentile for age group) ages 6-16 • Recruited from Center of Obesity and its Consequences on Health in Dallas, Texas • 89 non overweight children • Recruited from Endocrinology Center after being treated for hypothyroidism or GH deficiency, but otherwise healthy • Exclusion criteria: use of anticonvulsant, vitamin D supplement more than 400 IU/day, other relevant disorders
Data collected • Age, sex, ethnicity, height, weight, blood pressure, dietary habits • Laboratory data • Serum 25(OH)D • HbgA1C • Fasting glucose and insulin • OGTT • HOMA-IR
Statistical Analysis • Prevalence of Vit D insufficiency determined for obese and non-overweight populations within each ethnic group and season • Data collected in summer, fall, winter, spring • Sufficiency: 75 nmol/L • Insufficiency: < 75 nmol/L • Deficiency: < 50 nmol/L • χ squared to determine prevalence rate
Statistical Analysis cont. • Two way ANOVA to compare 25(OH)D between groups and assess interaction btw obesity and season; gender and ethnicity • Pearson coefficients used to determine relationship btw 25(OH)D and: • 2h glucose • HbbA1c • HOMA-IR • Blood pressure
Results Vitamin D deficiency + inadequacy
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= >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
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
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
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
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