Low levels of vitamin D appear to increase a child's risk of anaemia, according to a new study.
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.
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 per cent vs 2 per cent) 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.
