Newborn babies with low levels of vitamin D face an increased risk of respiratory infections during infancy and wheezing episodes during early childhood, according to a new study.
By the age of three months, infants whose vitamin D levels were very low were twice as like to have developed respiratory infections as those whose vitamin D levels were among the highest of babies in the study.
But low vitamin D levels weren’t associated with an increased risk of developing asthma, researchers said.
"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," said study researcher Dr. Carlos Camargo, of the Massachusetts General Hospital in Boston, in a statement.
Such infections could be taking hold because vitamin D is important in immunity, the researchers said. Although the vitamin is commonly associated with maintaining strong bones, recent evidence suggests that it is also a critical element of a strong immune system.
Previous studies by Camargo suggested that children of women who took vitamin D supplements during pregnancy were less likely to develop wheezing than children whose mothers did not take vitamin D supplements. The new study revealed the link held up when researchers looked at the newborns’ blood levels of vitamin D.
The researchers gathered data from 922 children who were part of the New Zealand Asthma and Allergy Cohort Study. Researchers analyzed umbilical cord blood collected and analyzed at birth for levels of a compound called 25-hydroxyvitamin D (25OHD) – the higher the levels of 25OHD in the blood, the more vitamin D in the body.
The researchers also asked the mothers about their children's respiratory and infectious diseases, including whether they’d seen their kids wheezing, when the children were three months old, 15 months old, and then annually until the children were five years old.
More than 20 percent of the children had 25OHD levels less than 25 nanomoles per liter of blood, which is considered a very low amount of vitamin D. (The average level of 25OHD is 44 nanomoles per liter of blood; children whose 250HD levels are higher than 100 nanomoles per liter are considered to have enough of the nutrient).
Researchers also found that the lower the 25OHD level of infants when they were born, the higher their risk of wheezing was in the next five years.
However, there was no association between the diagnosis of asthma at 5 years and low 25OHD levels, the study said.
Vitamin D is produced by the body in response to sunlight, and achieving adequate levels in winter can be challenging, especially in regions with low levels of sunlight, researchers said.
Next, Camargo hopes to test to see whether vitamin D supplements can help to prevent asthma caused by respiratory infections, particularly during the fall and winter when vitamin D levels decline.
Pass it on: Infants born with low levels of vitamin D are more likely to develop wheezing and respiratory infections than babies with regular vitamin D levels.
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