Vitamin D deficiency in obese children and adolescents and relation to glucose homeostasis

Abstract

Background: Obesity is the primary risk factor for development of impaired glucose tolerance, and metabolic syndrome. Obese children and adolescents are at an increased risk of vitamin D deficiency because it is sequestrated by excess adipose tissue, thus lowering its bioavailability. Vitamin D is critical in both glucose homeostasis and insulin secretion. Objective: to compare the prevalence of vitamin D deficiency in obese and lean children and adolescents and to evaluate the relation between 25 (OH) D level and markers of abnormal glucose metabolism. Methods: This cross‐sectional controlled study included 40 obese children and adolescents (age, 3‐ 14 years; BMI ≥ 95th percentile for age) randomly recruited from the Obesity Clinic, Children's Hospital, Ain‐ Shams University and 40 age‐, sex‐, ethnicity‐ and season‐ matched healthy lean subjects served as controls. Clinical evaluation including blood pressure and different anthropometric measurements of patients and controls including weight, height, waist and hip circumferences and waist/hip ratio. Fasting serum glucose and insulin, fasting lipids and 25‐ OHD were measured. The homeostatic model assessment of insulin resistance (HOMA‐IR) was calculated in both groups. Results: The obese subjects had higher fasting glucose and significantly higher fasting insulin (p‐ value= 0.000), also they had significantly higher HOMA‐IR (p‐value= 0.000), higher LDL‐ cholesterol levels (p=0.000), triglycerides and significantly lower HDL‐ cholesterol levels than controls (p=0.000). The levels of 25‐OHD in the obese group (16.74±16.33ng/dl) were significantly lower than those of the controls (77.44±44.4ng/dl) (p=0.000). A significant negative correlation was found between 25(OH)D and HOMA‐IR in obese subjects (r= ‐0.192, p=0.000). Conclusion: Vitamin D deficiency is common in Egyptian children and is significantly more prevalent in obese children.