Researchers led by investigators at the Johns Hopkins Children's Center studied blood samples from more than 10,400 children, tracking levels of vitamin D and hemoglobin, the oxygen-binding protein in red blood cells. (Agencies)
Vitamin D levels were consistently lower in children with low hemoglobin levels compared with their non-anaemic counterparts, researchers found.
The sharpest spike in anaemia risk occurred with mild vitamin D deficiency, defined as vitamin D levels below 30 nanograms per millilitre (ng/ml).
Children with levels below 30 ng/ml had nearly twice the anaemia 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 anaemia, 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 anaemia.
Investigators also looked at anaemia and vitamin D by race, and an interesting difference emerged.
Black children had higher rates of anaemia compared with white children (14 percent vs 2 percent) and considerably lower vitamin D levels overall, but their anaemia 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 anaemia 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 paediatric kidney specialist at the Johns Hopkins Children's Center.
The study was published in the Journal of Pediatrics.
Researchers led by investigators at the Johns Hopkins Children's Center studied blood samples from more than 10,400 children, tracking levels of vitamin D and hemoglobin, the oxygen-binding protein in red blood cells.