Vitamin D deficiency and childhood asthma

Researchers from the Telethon Kids Institute have found that children with vitamin D deficiency are more likely to develop asthma.

The team’s study, published in the Journal of Allergy and Clinical Immunology, saw the researchers track vitamin D levels from birth to age 10 in Perth children at high risk for asthma and allergy. According to lead author Dr Elysia Hollams, it was the first ever study to track vitamin D levels from birth to asthma onset.

“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.”

According to Dr Hollams, the study showed “a clear link between prolonged vitamin D deficiency in early childhood and the development of asthma”. 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.

“We’ve also shown 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,” said Dr Hollams.

Dr Hollams referred to previous research which 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”. The new study identifies vitamin D deficiency as “a co-factor that may promote this process”.

However, she noted that there are still many unknowns in the field of vitamin D research, saying, “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.”

Commenting on the study, Professor Katie Allen from the Murdoch Childrens Research Institute wondered if the findings signal a need for 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,” she said, “and therefore it may not be a coincidence that we have the highest rates of allergic disease, including food allergies, in the developed world.”

Professor Prue Hart, a co-author on the study, meanwhile said that UV radiation from sunlight is the best natural source of vitamin D, but warned that people should know their skin type and should not ignore sun-safe guidelines — especially in a country like Australia.

“It’s all about finding a safe and sensible balance between exposure and need,” said Professor Hart.

Image courtesy of NIAID under CC BY 2.0