Low levels of vitamin D in newborns are found to increase the risk of respiratory infections and wheezing, but not asthma, suggests researchers and found in a large cohort study.
According to the study authors, respiratory infections pose health risks for children . Carlos Camargo, MD, DrPH, of the Massachusetts General Hospital (MGH), who led the study explains, “For example, bronchiolitis – a viral illness that affects small airway passages in the lungs – is the leading cause of hospitalization in U.S. infants."
In a cohort analysis of 922 newborns, the scientists found double the rates of respiratory infection and wheezing by age 3 months among infants with 25-hydroxyvitamin D (25OHD) levels less than 25 nmol/L. The findings come from a New Zealand Asthma and Allergy Cohort Study that followed more than 1,000 children in the cities of Wellington and Christchurch. Midwives and study nurses collected cord blood that was analyzed for levels of 25-hydroxyvitamin D (25OHD) that is reflective of vitamin D status.
Past studies show that children whose mothers took vitamin D supplements during pregnancy were less likely to develop wheezing during childhood.
The current study examined the link between vitamin D levels in cord blood taken from newborns. The researchers gathered data via questionnaires submitted by the mothers, detailing the number of respiratory infections that developed in the first 5 years of life among the study participants.
Compared to infants whose 25OHD levels were 75 nmol/L or higher, there were twice as many respiratory infections reported. The follow-up times were age 3 months, 15 months, one year and annually up to age 5.
Lower levels of vitamin D were found among infants born during winter months and in infants and children with lower socioeconomic status, family histories of asthma and smoking. Twenty percent of newborns had 25OHD levels considered deficient - less than 25 nmol/L.
Overall, lower vitamin D levels at birth were linked to higher risk of wheezing during the first five years of life. There was no link between asthma and higher 25OHD levels, as suggested by some previous studies.
Camargo warns that doesn’t mean vitamin D has no role in asthma. He says, "There's a likely difference here between what causes asthma and what causes existing asthma to get worse.”
Even though infants with lower levels of vitamin D were found to have more wheezing and respiratory infections during the first five years of life, the authors say more research will be needed to see if supplementation can prevent the common ailment. They hope to conduct a large clinical trial next year.