Jan 02, 2010 – Infants at age 3 months who had newborn blood levels of 25-hydroxyvitamin D -- a measurement of vitamin D -- below 25 nanomoles per liter (nmol/L) were twice as likely to develop respiratory infections as infants who had levels at 75 nmol/L or higher, according to an international study published in the January issue of Pediatrics, a journal of the American Academy of Pediatrics.

That finding is based on umbilical cord blood samples taken from more than 900 infants to measure blood vitamin D levels. Earlier research has suggested that mothers who have higher levels of vitamin D in their blood during pregnancy are more likely to give birth to infants who are at a lower risk for wheezing.

Researchers found that:

• Lower vitamin D levels were more common among children born in the winter, children of lower socioeconomic status, children who had family histories of asthma and smoking and who had been exposed to secondhand smoke at an early age.
• Low vitamin D levels were associated with wheezing and respiratory infection, but not associated with being diagnosed with asthma. The findings do not establish cause and effect.

Benefits of Vitamin D

Vitamin D is known for helping children build strong bones, but it can also help bolster the immune system. Vitamin D is also produced by the body when exposed to sunlight.

Acute respiratory infections are a major health problem in children, the researchers say. Researchers want to evaluate whether vitamin D supplements could provide some benefit.

The study data suggest that the association between vitamin D and wheezing, which can be a symptom of many respiratory diseases and not just asthma, is largely due to respiratory infections. Since respiratory infections are the most common cause of asthma exacerbations, vitamin D supplements may help to prevent those events, particularly during the fall and winter, when vitamin D levels decline and exacerbations are more common. That idea needs to be tested in a randomized clinical trial.