Poor vitamin D status increases the risk of anemia in school children: National Food and Nutrition Surveillance

Highlights

• An association was found between low vitamin D status and increased risk of anemia in children independent of age, sex, or body mass index.

• Children with a vitamin D deficiency exhibited a rate of anemia that was nearly three times that of persons of similar age who were vitamin D sufficient.

• The risk of anemia increased in children with serum 25-hydroxyvitamin D concentrations below 44 nmol/L.

Abstract

Objectives

This study aimed to investigate the association between 25-hydroxyvitamin D (25[OH]D) concentrations and the risk of anemia in a large cohort of children with consideration for the effects of sex, body mass index (BMI), serum intact parathyroid hormone (iPTH) concentrations, and iron level status.

Methods

A total of 937 children (493 boys, 444 girls) ages 9 to 12 y were enrolled in a cross-sectional study. The children underwent various examinations including anthropometric measurements and blood sampling.

Results

Overall, 13.3% of the children were anemic and 64.2% and 28.1% of the subjects had a vitamin D deficiency (<25 nmol/L) and insufficiency (25–50 nmol/L), respectively. Approximately 13% of the children had concurrent low hemoglobin and hypovitaminosis D levels. The prevalence of hypovitaminosis D in the group of children with anemia was 96.8% compared with 91.6% in the non-anemic group (P = 0.046). Mean 25(OH)D concentrations were significantly lower in the anemic children compared with the non-anemic children (19.6 ± 13.3 vs. 24.0 ± 23.1 nmol/L; P = 0.003). After controlling for sex and BMI, children with a vitamin D deficiency were almost 3.45 times more likely to be anemic compared with children with a vitamin D sufficiency (95% confidence interval [CI], 1.21–9.81). The increased risk of anemia was found to start significantly at 25(OH)D < 44 nmol/L (17.6 ng/mL; odds ratio: 2.29; 95% CI, 1.07–4.91, P = 0.032).

Conclusions

These findings strongly suggest an association between low circulating concentrations of 25(OH)D and anemia in a large, representative sample of children, even after adjustment for sex, age, BMI, and iPTH.

Introduction

Despite the dramatic improvement of public health facilities and elimination of many nutritional deficiencies at the population setting, iron and vitamin D deficiencies are still both prevalent in many communities. However, the potential relationship between these two micronutrients has not been elucidated to date [1].

Vitamin D deficiency (VDD) is an important public health issue, especially with the new insights into the clinical consequences of VDD in a number of diseases such as diabetes, osteoporosis, hypertension, cancer, and cardiovascular disease [1]. Results from the National Food and Nutrition Surveillance show that hypovitaminosis D is highly prevalent in the population of Iran, and approximately 93% of children exhibit suboptimal circulating calcidiol concentrations (i.e., serum 25-hydroxyvitamin D [25(OH)D] concentrations <50 nmol/L) [2].

Despite knowledge of the causes and the availability of treatment approaches, iron deficiency and consequent anemia are both increasingly recognized as highly common health problems around the world, especially in women and children [3], [4]. In 2010, anemia accounted for 8.8% of the total disability from all conditions [5]. Anemia affects 1.62 billion people, including 47.4% of preschool children and 35% (468.4 million) of non-pregnant women around the world [6]. The National Health and Nutrition Examination Surveys (2003–2006) also found the incidence of anemia in children and female adolescents to be 3.7% to 4.5% and 9.3% to 15.6%, respectively [7].

Anemia may cause increased morbidity and mortality and diminished quality of life either directly or as a risk factor of other causes [4]. The role of vitamin D in iron homeostasis and erythropoiesis has emerged in recent years [8], [9]. Vitamin D may be associated with hemoglobin concentrations and anemia in various healthy and diseased populations [9], [10], [11], [12].

Recently, Lee et al. used data of 2526 children and adolescents ages 10 to 20 y from the Korea National Health and Nutrition Examination Survey-V (2010–2012) and reported that VDD was associated with an increased risk of anemia, especially iron deficiency anemia (IDA), in healthy female children and adolescents [13]. Atkinson et al. also showed that an increased prevalence of VDD was associated with an increased risk of anemia in healthy children. However, the researchers suggested a possible differential sensitivity to the effects of vitamin D by race [14]. Children ages 9 to 12 y (i.e., preteens) begin to show signs of puberty with increased nutritional needs, especially micronutrients such as iron. Therefore, our objective was to investigate the association of 25(OH)D concentrations with the risk of anemia in a large sample of Iranian children to evaluate the effects of sex, body mass index (BMI), and iron status. The intertwisted metabolism of vitamin D and parathyroid hormone (PTH) as well as the importance of PTH determination in the assessment of vitamin D status [15] and serum intact parathyroid hormone concentration was also assayed.