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

Research has begun to unveil a role for vitamin D in iron homeostasis and erythropoiesis. Abundant vitamin D receptors exist in bone marrow, where vitamin D may directly activate erythroid precursor cells. Vitamin D may additionally suppress pro-inflammatory cytokines that contribute to anemia. As children approach the teenage years (between the ages of 9 and 12), they experience an increased demand for iron and other micronutrients. This cross-sectional study explored the association between 25-hydroxy vitamin D (25[OH]D) and anemia in a large cohort of Iranian children.

Methods

The study evaluated blood and anthropomorphic parameters in 937 children (aged 9-12). Anemia was defined as hemoglobin < 11.5 g/dL, iron-deficient anemia (IDA) was defined as anemia with ferritin < 15 micrograms/L, and at risk for IDA was defined as ferritin < 15 micrograms/L without anemia. Vitamin D sufficiency was defined as 25(OH)D > 50 nmol/L, insufficiency was defined as 25 to 50 nmol/L, and deficiency was defined as ≤ 25 nmol/L.

Vitamin D can be produced by the skin from exposure to sunlight.

Results

Overall, 13.3% of the children had anemia (10.8% of girls and 15.6% of boys), 12.8% were at risk of IDA, and 3.2% had IDA. Regarding vitamin D status, 64.2% had vitamin D deficiency, 28.1% had vitamin D insufficiency, and only 7.7% had vitamin D sufficiency. Mean 25(OH)D concentrations were significantly lower in the anemic children than in the non-anemic children (19.6 nmol/L vs 23.1 nmol/L; p=.003). After controlling for sex, body mass index, and intact parathyroid hormone, children with vitamin D deficiency were 3.45 times more likely to be anemic than children with vitamin D sufficiency (95% CI, 1.21-9.81). The increased risk of anemia started significantly at 25(OH)D < 44 nmol/L. 

Conclusions

The results of this study are congruent with previous population-based studies of micronutrient status in children, although US statistics have been somewhat less dire. The United States National Health and Nutrition Examination Surveys (NHANES), for example, found the incidence of anemia in children and teens to range from 4% to 16% and the incidence of vitamin D sufficiency to be as high as 67%. Still, this study brings to light an important association between vitamin D deficiency and anemia, a finding that could have significant clinical importance for children and teens. 

Nikooyeh, B., & Neyestani, T.R. (2018). Poor vitamin D status increases the risk of anemia in school children: National Food and Nutrition Surveillance. Nutrition, 47, 69-74.