OLSON, M.L . , ET AL

Vitamin D Deficiency in Obese Children an Its Relationship to

Glucose Homeostasis

J CL IN ENDOCRINOL METAB, 97 , 279 -285 , 2012

Researchers

5.967 Impact FactorInternal MedicinePediatric 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 Clin Endocrinol Metab 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, Texas89 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

Calculating Pediatric BMI

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

Study Subject Analysis

Study Subject Analysis

Study Subject Analysis

Results

Results

Vitamin D deficiency + inadequacy

Results

Results

Discussion

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

AgeBMIGenderEthnicitySeasonDietary 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