The findings, published in the Journal of Allergy and Clinical Immunology, showed repeated bouts of vitamin D deficiency in early childhood were linked to higher rates of asthma at aged 10, as well as allergy and eczema.
The study also found that allergic immune responses were more common in children with low vitamin D in the first few years, while children with vitamin D deficiency at 6 months of age were more likely to experience two conditions previously associated with heightened asthma risk: increased colonisation of the upper airways by harmful bacteria and increased susceptibility to severe lower respiratory infections involving fever.
Lead author Dr Elysia Hollams from the Telethon Kids Institute said the findings shed new light on a contested area of research.
“We know vitamin D plays an important role in regulating the immune system and promoting healthy lung development,” said Dr Hollams.
“But while it has been suggested that inadequate vitamin D may be a factor contributing to the surge in asthma rates over recent decades, previous studies investigating the relationship have yielded conflicting results. There has been a lack of research looking at whether vitamin D deficiency is more detrimental at certain periods in childhood.”
She said the study was the first to track vitamin D levels from birth to asthma onset, and it had shown a clear link between prolonged vitamin D deficiency in early childhood and the development of asthma.
The paper states that the children were assessed at birth and at clinical follow-ups at the ages of 0.5, 1, 2, 3, 4, 5, and 10 years, and relationships with clinical outcomes were examined.
“Vitamin D deficiency in early childhood is associated with increased risk for persistent asthma, potentially through modulating susceptibility to early allergic sensitization, upper respiratory tract colonization with bacterial pathogens, or both. These relationships are only evident if vitamin D status is monitored prospectively and longitudinally,” the study concluded.
According to Dr Hollams, this shows for the first time that babies deficient in vitamin D have higher levels of potentially harmful bacteria in their upper airways, and are more susceptible to severe respiratory infections.
“Earlier research by our team and others around the world has identified the first two years of childhood as a critical period during which allergies and chest infections can combine to drive asthma development in susceptible children. Our new findings identify vitamin D deficiency as a co-factor that may promote this process,” she said.
Role of supplements
She added, however, there were still many unknowns in the field of vitamin D research and questioned if supplementation was the answer.
“We still don’t know what the optimal level of vitamin D is for good lung health and immune function, and we don’t know if supplementation would address this issue, or if healthy sun exposure is what is required, given that vitamin D is an indirect measure of recent sun exposure,” she said.
But responding to the study, Professor Katie Allen, the Gastro and Food Allergy theme director at Murdoch Childrens Research Institute, said the findings raised the question of whether there should be increased Vitamin D exposure through the diet.
“Australia is one of the few developed countries that does not fortify its food supply with Vitamin D and therefore it may not be a coincidence that we have the highest rates of allergic disease, including food allergies, in the developed world.
“We believe that Vitamin D supplementation trials in infancy are essential to answer this important public health question,” she said.
“Vitamin D over the first decade and susceptibility to childhood allergy and asthma.”
Authors: Hollams Elysia M, et al