Elsevier

Nutrition

Volume 30, Issue 9, September 2014, Pages 1040-1044
Nutrition

Applied nutritional investigation
Vitamin D status and its association with adiposity and oxidative stress in schoolchildren

https://doi.org/10.1016/j.nut.2014.02.024Get rights and content

Abstract

Objective

The aim of this study was to evaluate serum 25-hydroxyvitamin D [25(OH)D] level and its association with adiposity, inflammation, and oxidative stress in schoolchildren.

Methods

A total of 1488 schoolchildren ages 7 to 11 y were recruited in Harbin, China (latitude: 44°04N–46°40N) in May. Serum 25(OH)D, which is an indicator of vitamin D status, was determined. Anthropometric data were collected following general physical examinations. Serum lipids, glucose metabolism indices, inflammatory molecules, and oxidative stress markers were determined. Dietary intake and physical activity also were assessed.

Results

The median serum 25(OH)D concentration was 18.4 ng/mL. Of the 1488 schoolchildren included, 839 (56.4%) had vitamin D deficiency [25(OH)D < 20 ng/mL]. Children in the vitamin D deficiency group had significantly higher body weight (34.1 ± 3.8 versus 31.5 ± 3.3 kg; P < 0.001), body mass index (18.4 ± 2.2 versus 16.8 ± 1.7 kg/m2; P < 0.001), waist circumference (60.1 ± 8.5 versus 57.2 ± 7.7 cm; P < 0.001), percentage of body fat (20.2% ± 2.6% versus 19.1% ± 2.4%; P < 0.001), and significantly lower concentrations of serum superoxide dismutase (95.38 ± 12.22 versus 127.62 ± 15.98 U/mL; P < 0.001) compared with those in the vitamin D sufficiency group. After adjusting for sex, age, body mass index, and percentage of body fat, a positive association between serum 25(OH)D and superoxide dismutase was found (β = 0.230; P < 0.001).

Conclusions

Vitamin D deficiency is common in Harbin schoolchildren. Serum 25(OH)D is closely associated with adiposity and superoxide dismutase in schoolchildren, suggesting that vitamin D deficiency potentially increases the risk for diseases caused by higher adiposity and oxidative stress.

Introduction

Increasing evidence suggests that vitamin D has multiple biological functions [1] in addition to regulation of calcium, phosphorus, and bone metabolism. 25-Hydroxyvitamin D [25(OH)D] is regarded as the best indicator of vitamin D status. Although there is no consensus on optimal levels of 25(OH)D in serum, most experts define vitamin D deficiency as a 25(OH)D concentration < 20 ng/mL [2]. In China, little is known about the prevalence of vitamin D deficiency in school-aged children.

Previous studies in adults suggested a negative association between serum 25(OH)D and adiposity [3], [4]. However, it remains unclear whether a similar association between serum 25(OH)D and adiposity also exists in school-aged children, especially considering that vitamin D insufficiency in children is common in various parts of the world [5].

Excess fat gain often is accompanied by low-grade inflammation and oxidative stress. Additionally, the anti-inflammatory and antioxidative effects of vitamin D have been described in a series of in vitro and in vivo studies. Vitamin D has been shown to have a role in T-cell–mediated immunity and inflammatory response, and has beneficial effects in improving various autoimmune diseases [6]. It also has been reported that vitamin D has a significant protective role against cellular stress [7], and may function as an antioxidant in the liver [8]. However, the associations between serum 25(OH)D levels and biomarkers of inflammation and oxidative stress were rarely reported in large-scale cross-sectional studies of school-aged children.

Therefore, the aim of this study is to assess serum 25(OH)D level and its association with adiposity, inflammation, and oxidative stress in schoolchildren living in North China.

Section snippets

Participants

The participants in this school-based cross-sectional study were schoolchildren ages 7 to 11 y. Six schools were randomly selected from all primary schools in Harbin, including two small-scale schools (n < 800), two middle-scale schools (n ≤ 800 and ≤ 1000, respectively), and 2 large-scale schools (n > 1 000). Two classes from each grade were randomly selected from grades 1 to 5 of each selected primary school. All students were free from physical disability, congenital diseases, and any

General characteristics of participants

General characteristics of the participants are summarized in Table 1. No significant difference in serum 25(OH)D concentration was found between boys (18.7 ng/mL, 95% confidence interval [CI], 6.9–33.5) and girls (18.1 ng/mL, 95% CI, 6.5–32.6). There was also no significant difference between boys and girls in the prevalence of vitamin D deficiency (56.2% versus 56.7%). Energy expenditure, duration of total physical activity, and dietary energy intake are also presented in Table 1.

Adiposity in groups with different vitamin D status

After

Discussion

Children are at high-risk for vitamin D deficiency. In the United States, it was reported that 47% of children ages 4 to 18 y suffer from vitamin D deficiency [25(OH)D < 50 nmol/L] in Philadelphia, and 48% of adolescent girls in Maine [15], [16]. Even in countries with significant sunshine, vitamin D deficiency in children is common. For example, data from Iran showed that 46.2% (72.1% in girls) of high school students had low serum 25(OH)D concentrations (<20 ng/mL) due to avoidance of

Conclusion

Poor serum 25(OH)D concentration, commonly found in schoolchildren in Harbin, is closely associated with higher adiposity and lower SOD concentration. These results suggest that school-aged children with vitamin D deficiency are at higher risk for diseases caused by higher adiposity and oxidative stress.

Acknowledgments

The authors acknowledge the researchers and medical personnel of Harbin Medical University for their efforts and collaboration in this study.

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    This study was supported by the National Natural Science Foundation of China (No. 81172649 and No.81130049). C-HS and YL were responsible for the conception, design, and data interpretation of the study. H-QZ was responsible for data collection, data analysis, data interpretation, and writing the first draft of the manuscript. J-HT, X-XL, XH, and Y-HH were responsible for data collection and data interpretation. All authors approved the final version of the manuscript. The authors declared no conflict of interest.

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