New research led by investigators at the Johns Hopkins Children's Center suggests that children who do not get enough vitamin D may be at higher risk for anemia. However, they caution that while their findings show a strong link, it does not mean one causes the other.
They say the results highlight the complex relationship between vitamin D and hemoglobin, the protein that holds oxygen in red blood cells.
They suggest that low vitamin D might be linked to anemia via several mechanisms, for example, the link might be the way the vitamin affects the production of red blood cells in bone marrow. Or it could be vitamin D's role in regulating immune inflammation, which is known to trigger anemia.
Anemia, a condition where the body does not have enough oxygen-carrying red blood cells, is thought to affect around 20% of children at some point in their lives.
And several large studies estimate that nearly 7 out of 10 American children do not have enough vitamin D, with around 1 in 10 suffering from severe deficiency.
'Double the anemia risk'
For their study, the team looked for links between vitamin and hemoglobin in the blood samples of over 10,400 children and adolescents (aged between 1 and 21 years) who took part in the 2001-2006 National Health and Nutrition Examination Survey (NHANES).
They found children with low hemoglobin levels consistently had lower levels of vitamin D, compared with children who had normal hemoglobin levels.
Children whose vitamin D levels were below 30 nanograms per milliliter (ng/ml), defined as mild vitamin D deficiency, had nearly double the risk of anemia than counterparts with normal vitamin D levels.
When they examined the results by race, they found black children had higher rates of anemia compared with white children, and much lower vitamin D levels overall, but their risk of anemia did not increase until their vitamin D levels were much lower than those of white children.
Lead investigator Dr. Meredith Atkinson, a pediatric kidney specialist at the Johns Hopkins Children's Center, says:
"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."
It is important to treat chronic anemia and vitamin D deficiency as they can lead to a range of health consequences, including organ damage, bone deformities and frequent fractures, as well as early development of osteoporosis later on in life.
The authors note that as well as being important for healthy bones, there is also evidence that vitamin D plays other roles - recent studies have found low levels of the vitamin are linked to cancer, heart disease and suppressed immunity.The research was funded by the National Institute of Diabetes, Digestive and Kidney Diseases.