Vitamin D deficiency has been linked to impaired lung function and could worsen symptoms of asthma and other respiratory disease symptoms in adults, a study has found.

Researchers from the University of Western Australia and Sir Charles Gairdner Hospital tested serum vitamin D levels, lung function and respiratory symptoms in more than 5000 baby boomers.

The participants all came from WA's South West region and are part of the Busselton Healthy Ageing Study.

Scientists found those with low levels had a higher instance of respiratory illnesses such as asthma and bronchitis.

They also found that high levels of Vitamin D were associated with better lung function, suggesting it plays an important role in maintaining good respiratory health.

And the effects of vitamin D on lung health remains the same even when seasonal fluctuation, obesity and the impact of chronic disease on vitamin levels were factored in.

Lead scientist Siobhain Mulrennan says there is emerging evidence that increasing vitamin D levels through lifestyle or supplements can reduce asthma symptoms and severity among those with inadequate levels.

A recent study, published in The Lancet Respiratory Medicine journal, found the use of the supplements lead to a 50 per cent drop in the number of people being admitted to a hospital emergency department because of an asthma attack.

DNA and data collected in the ongoing Busselton health study will allow further investigation into the genetic factors which influence vitamin D levels, BHAC chairman Alan James said.

However, BHAC director Michael Hunt says opinion is still divided as to whether vitamin D deficiency contributes to respiratory diseases or was a result of the existing disease or its treatment.

A follow-up study of the same study participants is currently underway.