Pioneering research using an animal model has found that vitamin D deficiency shortly before and after birth results in negative changes to the molecular and structural function of the lungs that are associated with asthma. The results also showed that vitamin D supplementation blocks these effects.
Asthma that occurs in childhood presents unique challenges. Childhood asthma is one of the leading causes of emergency department visit, hospitalizations, and missed school days.
Vitamin D status has been proposed to be one of the main factors that influences the development and/or severity of childhood asthma.
Lung development begins in utero and continues through the first few years of life. Experimental animal and human research suggests that vitamin D modulates fetal lung maturation and modulates the growth and development of the smooth muscles cells in the airways, processes that go awry in the smooth cells of children with asthma.
Moreover, recent epidemiological evidence shows that perinatal, the time shortly before and after birth, vitamin D deficiency is associated with childhood asthma.
It has never been shown experimentally, either in animal or humans, whether perinatal supplementation in mothers blocks development of asthma in offspring.
Researchers recently explored this area by using a rat model of vitamin D deficiency during pregnancy and lactation to assess the effects that deficiency during this period has on offspring lung structure and function. They also examined the effects of vitamin D supplementation during this period on the development of asthma.
To do this, they assigned female rats to four different dietary groups:
- A vitamin D-deficient group that did not have vitamin D added to their food.
- A group that received 250 IU/kg vitamin D in their food.
- A group that received 500 IU/kg vitamin D in their food.
- A high-dose group that received 1000 IU/kg vitamin D in their food.
The rats were started on these diets 4 weeks prior to becoming pregnant and the regimens were continued throughout pregnancy and into lactation until 21 days after giving birth.
At this point, the blood and lungs of the offspring were collected for analysis. They measured vitamin D levels from the blood.
The researchers assessed lung structure by measuring alveolar count. Alveolar count is the quantification of the amount of alveoli, which are tiny structures that are the site of gas exchange between the blood and lungs. In this context, a greater alveoli count indicates improvement in the lungs.
The researchers assessed lung function by measuring airway resistance following an allergen challenge and tracheal contraction response following administration of acetylcholine, a neurotransmitter. Increased airway resistance and increased tracheal contraction both indicate decreased lung function.
Did vitamin D supplementation improve lung function through an increase in alveoli count or a decrease in airway resistance and tracheal contraction?
Here’s what their analysis revealed:
- Vitamin D levels in the offspring were lowest in the vitamin D-deficient group and highest in the 1000 IU/kg vitamin group, displaying a dose-dependent increase.
- The alveolar count was significantly increased in the vitamin D-supplemented group compared to the vitamin D-deficient groups (p<0.05)
- Airway resistance was significantly increased in the vitamin D-deficient and 1000 IU/kg vitamin D groups compared to the 250 IU/kg and 500 IU/kg vitamin D groups (p<0.05).
- Of the three vitamin D-supplemented groups, only the 500 IU/kg vitamin D group saw a significant decrease in tracheal contractility compared to the vitamin D-deficient group (p<0.05).
The researchers summarized their results,
“Our study demonstrated that perinatal vitamin D deficiency causes offspring lung molecular and structural alterations, likely explaining the associated lung asthma phenotype. The altered lung structure and function, reflected by alterations in alveolar [count], [airway resistance], and tracheal contractility were largely blocked by 250 and/or 500 IU/kg VD dietary supplementation.”
This is the first study to experimentally demonstrate the structural and functional airway alterations occurring in the offspring of mothers with perinatal vitamin D deficiency and the prevention of these alterations with supplementation, dose-dependently.
Because this is an animal study, the results can’t be translated to human populations.
It is interesting to note that only the 250 IU/kg and the 500 IU/kg saw improvements in airway resistance, and only the 500 IU/kg groups saw improvement in tracheal contractility.
Some studies have suggested a detrimental effect of high dose perinatal supplementation of vitamin D on the development of asthma and allergies, which indicates that vitamin D may play a complex role in lung development.
Currently, on-going intervention trials are evaluating the effects of early life vitamin D supplementation at a range of doses, in differing populations, and using a range of treatment schedules. These trials should provide answers in establishing the clinical significance of perinatal vitamin D supplementation in preventing childhood asthma.