Hundreds of babies could be saved from "horrific" respiratory illnesses each year if vitamin D supplements were easier to access.
That's according to researchers of the Growing up in New Zealand study that found babies born with low levels of vitamin D were twice as likely to end up in hospital with a chronic respiratory condition.
Vitamin D helps babies build a strong immune system, which is crucial to a healthy respiratory system, University of Auckland Professor Cameron Grant told the Herald.
In New Zealand, it's difficult to absorb a healthy level of vitamin D due to our harsh sun rays and the government encourages us to avoid it due to the risk of skin cancer, Grant said.
Some foods contain small amounts of vitamin D - including oily fish, milk, eggs and liver.
While vitamin D supplements are government-funded, New Zealanders are still required to pay for a prescription after a visit to a GP. Supplements are also available to buy at the supermarket.
Pregnant women and babies were particularly susceptible to low levels of vitamin D as they were more likely to stay out of the sun, Grant said.
They should have free access to supplements for this reason, he said.
But Pharmac warned that excessive doses of vitamin D could result in severe toxicity and suggested handing them out could be dangerous.
Grant - who is also a paediatrician at Starship Hospital - said there wasn't enough awareness about the benefits of vitamin D and it wasn't being recommended by doctors enough.
He spoke of the horrific impact of serious respiratory illnesses.
"They come into hospital then they have multiple hospital admissions during the first year of their life and then some of them end up with ongoing chronic diseases that never go away and causes some of them to die younger than they would otherwise."
Pacific and Māori patients were even more at risk, he said.
These diseases could be prevented if babies and pregnant woman were getting sufficient levels of vitamin D, Grant said.
A low level of vitamin D was anything below 50ml per litre - 25ml per litre often landed patients in the emergency department.
Grant recommended every New Zealander to have one drop of vitamin D - elderly, pregnant woman and babies were more susceptible due to them spending less time in sunlight.
Another problem, Grant said, was the difficulty for patients and doctors to get vitamin D blood tests to identify if there is a low level present.
Laboratory tests were expensive and timely and were often discouraged, Grant said.
The Growing Up in New Zealand study looked at vitamin D levels from more than 1300 babies in the study at birth and then examined hospital data for respiratory admissions in the children's first year of life.
Out of the 384 babies with respiratory admissions, 52 per cent had low levels of vitamin D.
"This is completely preventable," Grant said.
About Growing Up in New Zealand
• Growing Up in New Zealand is a University of Auckland study, managed by UniServices Limited.
• The study is funded by the New Zealand government, through a contract with the Ministry of Social Development.
• It is the country's largest contemporary longitudinal study of child development.
• It follows more than 6000 children born in the Auckland, Counties Manukau and Waikato District Health Board areas in 2009 and 2010.
• The study has followed these children from before birth and intends to continue until the children are at least 21 years old.
• The study has been specifically designed to reflect the diverse lives of children growing up in the complex world of 21st-century New Zealand.