One in four adults in Australia is not getting enough Vitamin D which we get from sunlight and which helps fight disease.
This even though Australia gets plenty of sunshine - some areas get an average of eight hours a day - all year round.
Sunlight is the body's main source of this crucial vitamin - but health concerns are causing people to run for the shade.
So how much sun do you actually need, before it damages your skin? A new study aims to produce a definitive guidance on how to get the balance right.
Al Jazeera's Andrew Thomas reports from Melbourne.