Study Title:

Low Vitamin D and Viral Respiratory Infections in Infants

Study Abstract

Background:Respiratory syncytial virus (RSV) is the most important pathogen causing severe lower respiratory tract infection (LRTI) in infants. Epidemiologic and basic studies suggest that vitamin D may protect against RSV LRTI.

Objective:To determine the association between plasma vitamin D concentrations at birth and the subsequent risk of RSV LRTI.

Design:A prospective birth cohort study was performed in healthy term neonates. Concentrations of 25-hydroxyvitamin D (25-OHD) in cord blood plasma were related to RSV LRTI in the first year of life, defined as parent-reported LRTI symptoms in a daily log and simultaneous presence of RSV RNA in a nose-throat specimen.

Results:The study population included 156 neonates. Eighteen (12%) developed RSV LRTI. The mean plasma 25-OHD concentration was 82 nmol/L. Overall, 27% of neonates had 25-OHD concentrations <50 nmol/L, 27% had 50-74 nmol/L and only 46% had 25-OHD 75 nmol/L. Cord blood 25-OHD concentrations were strongly associated with maternal vitamin D3 supplementation during pregnancy. Concentrations of 25-OHD were lower in neonates who subsequently developed RSV LRTI compared with those who did not (65 nmol/L versus 84 nmol/L, P = .009). Neonates born with 25-OHD concentrations <50 nmol/L had a sixfold (95% confidence interval: 1.6-24.9; P = .01) increased risk of RSV LRTI in the first year of life compared with those with 25-OHD concentrations ≥75 nmol/L.

Conclusions:Vitamin D deficiency in healthy neonates is associated with increased risk of RSV LRTI in the first year of life. Intensified routine vitamin D supplementation during pregnancy may be a useful strategy to prevent RSV LRTI during infancy.

From press release:

Newborns with low vitamin D levels have a sixfold higher risk of lung infections with respiratory syncytial virus (RSV), Dutch researchers say.

RSV is the major cause of serious lung infections in infants. During the first 12 months of life, it's the most common cause of bronchiolitis (inflammation of the small airways in the lung) and pneumonia in the U.S.

Low vitamin D levels have been suspected of playing a role in vulnerability to RSV. This led Mirjam E. Belderbos, MD, of the Utrecht University Medical Center in the Netherlands, and colleagues to measure vitamin D levels in the cord blood of 156 newborns and then to follow the children for one year.

At birth, more than a quarter of the infants had low vitamin D -- serum levels of less than 20 ng/mL. During their first year of life, these kids had a sixfold higher risk of RSV lung infection than did the 46% of kids whose vitamin D levels at birth were at least 30 ng/mL.

"We demonstrated that 54% of healthy newborns in the Netherlands are born with insufficient [vitamin D] concentrations required for maximum health, and that low plasma concentrations of [vitamin D] are associated with increased risk of RSV lower-respiratory tract infections in the first year of life," Belderbos and colleagues report.

It's not just the Netherlands. Other Western nations, including the U.S., have similar rates of low vitamin D.

U.S. researchers reported in 2010 that at a single Boston hospital, 58% of infants and 36% of mothers had low vitamin D levels (under 20 ng/mL). Severe vitamin D deficiency (defined as lower than 15 ng/mL) was seen in 38% of the infants and in 23% of the mothers.

Slideshow: Amazing Vitamin D, Nutrition's Newest Star

Low Vitamin D and Childhood Disease
Vitamin D is a hormone that the body makes when exposed to direct sunlight. Belderbos and colleagues found that infants born in July had the highest vitamin D levels, while those born in December had the lowest levels.

RSV isn't the only problem for kids with low vitamin D. Vitamin D deficiency -- levels below 12 ng/mL -- causes the soft, weak bones of rickets. Rickets was common in the days before vitamin D was added to milk.

But low vitamin D during pregnancy may play a role in a wide range of diseases in children: type 1 diabetes, multiple sclerosis, schizophrenia, infant wheeze, and respiratory infections.

How can vitamin D affect infections? Belderbos and colleagues suggest three ways:

Vitamin D plays a role in the development of the fetal and infant immune system.
Vitamin D may accelerate early lung development.
Vitamin D has antimicrobial properties.
Just under half of the women in the Dutch study took vitamin D3 supplements. Infants born to these women had significantly higher vitamin D levels at birth. However, the study was too small to show whether maternal vitamin D supplements protected infants from RSV lung infection.

The researchers call for clinical trials to test whether vitamin D supplements during pregnancy can protect children from RSV.

Study Information

Mirjam E. Belderbos, Michiel L. Houben, Berry Wilbrink, Eef Lentjes, Eltje M. Bloemen, Jan L. L. Kimpen, Maroeska Rovers, and Louis Bont
Cord Blood Vitamin D Deficiency is Associated With Respiratory Syncytial Virus Bronchiolitis
2011 May
Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, Netherlands.

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