Vitamin D Predicament in Obese Children and Adolescents

Vitamin D levels are significantly lower in obese children and adolescents compared to non-obese matching peers. While evaluating the number of obese and non-obese cases who improved upon vitamin D supplement, obesity was found to pose a risk for not receiving benefit from the vitamin D supplementation. Vitamin D given to these vulnerable groups results in a significantly attenuated increase in 25(OH)D levels with supplementation. However, the proper dose and duration cannot be deduced because several of the studies reported a portion of vitamin D deficient obese children and adolescents at the end of their supplementation period. Screening for vitamin D levels is thus recommended since obese children and adolescents are more prone to be deficient. Additionally, the dose and duration of vitamin D supplementation or treatment should follow the guidelines. Finally, it is prudent to hypothesize that if the published studies had performed simultaneous weight adjustment strategies more of the enrolled obese participants would have reached vitamin D sufficiency by the end of the supplementation trial coupled with the favorable changes in their BMI.

Vitamin D levels are significantly lower in obese children and adolescents compared to non-obese matching peers. While evaluating the number of obese and non-obese cases who improved upon vitamin D supplement, obesity was found to pose a risk for not receiving benefit from the vitamin D supplementation. Vitamin D given to these vulnerable groups results in a significantly attenuated increase in 25(OH)D levels with supplementation. However, the proper dose and duration cannot be deduced because several of the studies reported a portion of vitamin D deficient obese children and adolescents at the end of their supplementation period. Screening for vitamin D levels is thus recommended since obese children and adolescents are more prone to be deficient. Additionally, the dose and duration of vitamin D supplementation or treatment should follow the guidelines. Finally, it is prudent to hypothesize that if the published studies had performed simultaneous weight adjustment strategies more of the enrolled obese participants would have reached vitamin D sufficiency by the end of the supplementation trial coupled with the favorable changes in their BMI.

Mini Review
Many previous worldwide studies pointed out the decreased 25-hydroxy vitamin D [25(OH)D] levels that occur in obese adolescents compared to normal weight controls [1][2][3]. Lower concentrations of serum 25(OH)D levels in obese subjects may be explained by enhanced uptake by adipose tissue and increased metabolic clearance, and it is suggested that the sedentary lifestyle of obese subjects could be associated with less outdoor activity and less exposure to sunlight [4,5]. There was no consensus  Tables 1 & 2. Two of these studies gave vitamin D supplementation dose according to the guidelines which is 1200-2000 IU daily for obese pediatric age patients [12]. One gave a daily dose of 400 IU which is even less than the updated RDA of vitamin D in this age group (600 IU) according to the global consensus recommendations by [13]. The last three gave higher doses of vitamin D; two of them provided 28000 IU weekly either for 180 days or 12 weeks, and in the third 50000 IU was given weekly for 12 weeks. Although all six studies were managing obese children and adolescents with deficient vitamin D status, only the latter three studies provided a treatment dose which is between 3000-6000 IU daily according to the global consensus recommendations by [13]. Table 1.

What Is Known
Children and adolescent obesity are a risk factor for compromised vitamin D status.
Many previous clinical trials measured effect of vitamin D supplementation on vitamin D level in such vulnerable groups.

What Is New
The need to follow the recent guidelines in both dose and duration of vitamin D supplementation in these risk groups.
The results of simultaneous weight reduction strategies should be highlighted in clinical trials involving vitamin D supplementation in obese individuals. The study of Belenchia, et al. [8], which performed the longest supplementation period among the previous six studies, reported that only 93% of those receiving vitamin D supplementation became sufficient after 6 months. A more alarming number was reported by Javed et al. [11] who found that 75% of their vitamin D supplemented children and adolescents did not reach vitamin D sufficiency by the end of the 12-week supplementation trial.
Additionally, Harel, et al. [14] reported Future supplementation studies should thus be designed to include weight management program for such vulnerable ages to help achieve better vitamin D levels coupled by the expected BMI favourable changes.

Funding
None.