Vitamin D levels were consistently lower in children with low hemoglobin levels compared with their non-anemic counterparts, researchers found.
The sharpest spike in anemia risk occurred with mild vitamin D deficiency, defined as vitamin D levels below 30 nano grams per millilitre (ng/ml).
Children with levels below 30 ng/ml had nearly twice the anemia risk of those with normal vitamin D levels. Severe vitamin D deficiency is defined as vitamin D levels at or below 20 ng/ml. Both mild and severe deficiency requires treatment with supplements.
The researchers cautioned that their results are not proof of cause and effect, but rather evidence of a complex interplay between low vitamin D levels and hemoglobin.
The investigators said several mechanisms could account for the link between vitamin D and anemia, including vitamin D's effects on red blood cell production in the bone marrow, as well as its ability to regulate immune inflammation, a known catalyst of anemia.
Investigators also looked at anemia and vitamin D by race, and an interesting difference emerged.
Black children had higher rates of anemia compared with white children (14 per cent vs 2 per cent) and considerably lower vitamin D levels overall, but their anemia risk didn't rise until their vitamin D levels dropped far lower than those of white children.
The racial difference in vitamin D levels and anemia suggests that current therapeutic targets for preventing or treating these conditions may warrant a further look, the researchers said.
"The clear racial variance we saw in our study should serve as a reminder that what we may consider a pathologically low level in some may be perfectly adequate in others, which raises some interesting questions about our current one-size-fits-all approach to treatment and supplementation," said lead investigator Meredith Atkinson, a pediatric kidney specialist at the Johns Hopkins Children's Center.
The study was published in the Journal of Pediatrics.