Midday shade boosts vitamin D

People can get their daily requirement of vitamin D by sitting in the shade in the middle of the day according to research conducted by University of Southern Queensland (USQ) Centre for Rural and Remote Area Health Research Fellow Dr David Turnbull.

Dr Turnbull is conducting a study into how to optimise levels of UV exposure.

‘People are constantly saying don’t expose yourself to the sun too much and don’t go outside between 8am and 5pm. The current guidelines suggest you need to expose to a bit before 10am and after 3pm.

‘My research says the best time is in the middle of the day, if you sit in the shade.'

Dr Turnbull said people are able to still absorb UV radiation in the shade due to atmospheric scattering.

‘In the middle of the day you get more radiation for vitamin D because the sun is directly overhead and has less atmosphere to pass through. In the early morning and late afternoon there is more atmosphere to pass through.'

Dr Turnbull said sitting in the shade also reduces UVA rays which do not contribute to vitamin D absorption and cause harmful effects to humans.

Widely-known effects of the UVA rays include skin cancer, DNA damage, immune suppression, erythema and sun-related eye disorders.

However, complications which can arise due to a lack of vitamin D are less well known.

‘In the US between 50,000 and 60,000 people die each year because of issues related to not getting enough sun exposure,' Dr Turnbull said.

Studies have indicated a lack of vitamin D can contribute to breast cancer, prostate cancer, colorectal cancer, multiple sclerosis, diabetes, bacterial infections, inflammatory bowel disease, elevated cholesterol and rheumatoid arthritis.

Dr Turnbull recently returned from conferences in the United Kingdom (UK) and Switzerland where he presented early findings from his research into solar radiation.

‘No one has ever done this research before, so my presentations received a lot of interest.'

Currently Australia is lagging behind other countries in dedicating resources to research into solar radiation.

‘Thousands of people are working on this area overseas. There would be less than 20 working on it in Australia. We need to catch up. It is so hard to get funding.'

Through his research Dr Turnbull aims to reduce the knowledge gap in maximising vitamin D absorption while minimising harmful UV wavelengths to improve recommendations about sun exposure. 

Editor's Note: Original news release can be found here.