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- Open Access
Age and seasonal variation of serum vitamin D levels in healthy school children and adolescents
© Kim et al; licensee BioMed Central Ltd. 2013
- Published: 3 October 2013
- School Child
- Aged Group
- Serum Vitamin
- Outdoor Activity
Vitamin D is an important fat-soluble vitamin that functions as a prohornone and affects bone mineralization and calcium homeostasis. In this study, we measured serum vitamin D levels in healthy school children and adolescents, and evaluated the prevalence of vitamin D defficiency, and its correlation with age, season and other clinical parameters.
We included 706 school children and adolescents aged 7 to 18 years (434 girls and 272 boys) from March 2011 to February 2012. We excluded subjects with any acute or chronic diseases. None of subjects were taking calcium or vitamin D supplements. They were classified according to age (elementary school, 7-12 years old, n=565; middle school, 13-15 years old, n=75; high school, 16-18 years old, n=36), sex (boys, n=272; girls, n=434) and season (spring, March to May, n=267; summer, June to August, n=106; fall, September to November, n=139; winter, December to February, n=194). We performed anthropometric measurement and laboratory tests including fasting lipid profile (cholesterol, triglyceride and LDL cholesterol), ALP, Ca, P and serum 25OHD3 level. Vitamin D deficiency were defined as a serum 25OHD3 level lesser than 20 ng/mL.
1)In total 706 subjects, mean serum vitamin D level was 16.30 ± 6.10 ng/mL, and prevalence of vitamin D defficiency was 74.5%. The serum vitamin D level was negatively correlated with age, serum estradiol and LH values.
2)Mean serum vitamin D levels were 16.65 ± 6.07 ng/mL in elementary school group, 15.23 ± 6.37 ng/mL in middle school group, and 12.65 ± 5.56 ng/mL in high school group. The prevalence of vitamin D deficiency in 3 aged groups was 72.9% in elementary school group, 78.7% in middle school group, and 91.7% in high school group. However, in elementary school group, there was no significant difference in vitamin D levels between low grade (7-9 years old) and high grade subjects (10-12 years old).
3)The level of serum vitamin D was significantly higher in summer (20.99 ± 6.40 ng/mL) and fall (19.11 ± 6.11 ng/mL) than in spring (15.46 ± 5.22 ng/mL) and winter (12.88 ± 4.37 ng/mL). The prevalence of vitamin D deficiency was 93.8% in winter and 49.1% in summer.
4)Mean serum vitamin D level was significantly lower in girls (15.73 ± 5.71 ng/mL) than in boys (17.20 ± 6.59 ng/mL). The prevalence of vitamin D deficiency was 68.8% in boys and 78.1% in girls.
The prevalence of vitamin D deficiency in healthy school children and adolescent was very high, especially in high school adolescents and winter season. These findings suggest that adequate outdoor activity and vitamin D supplements should be necessary for school children and adolescents.
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.