Vitamin D – Your Best Defence Against The Flu

Vitamin D – Your Best Defence Against The Flu

Margaret Jasinska

This winter thousands of Australians will come down with influenza, otherwise known as the flu. By ensuring you have optimal blood vitamin D levels, you are setting yourself up for the best defence from becoming infected.

The flu is caused by a specific group of RNA viruses and can be spread by an infected person coughing or sneezing. You can also catch the flu from touching an item contaminated by the virus.

Human Anatomy

Did you know that the flu virus can survive for more than eight hours on hard surfaces like plastic or stainless steel, and more than an hour in the air of a closed room?

You can see how incredibly easy it is to pick up an infection if you touch money, door handles, or use public transport!

Human Anatomy

There is a big difference between a cold and the flu.

A cold is much less severe. The flu tends to come on suddenly and can make you feel like you’ve been hit by a bus. It causes a high fever and there is usually loss of appetite and coughing. The flu leaves you flat on your back, unable to work or study.

You may not realise that Influenza causes 1,500 to 3,500 deaths in Australia each year. A new flu vaccine is developed annually, however, because the viruses responsible mutate so quickly, the vaccine is often not effective.

Vitamin D is a powerful ally in helping to keep you flu-free this winter.

You probably know that vitamin D is critical for keeping your bones strong, but did you know it benefits your immune system?

Human Anatomy

Your white blood cells contain vitamin D receptors. When vitamin D binds to them, it causes the release of antimicrobial proteins that help your body fight invading viruses and germs.

People with lower blood vitamin D levels are more susceptible to getting sick, and tend to have a more severe infection.

A study conducted on healthy adults found that people with lower levels of vitamin D were twice as likely to get the flu, compared to people with high levels.

Vitamin D insufficiency is surprisingly common in sunny Australia, particularly in winter. You make vitamin D in your skin when you are exposed to the sun’s UVB rays. Midday is when UVB rays are strongest, and this is the time when many people are indoors working.

In much of Australia the sun is too weak during winter, therefore even if you are outdoors a lot, you could still be low in vitamin D. A vitamin D supplement may be your best option for keeping your immune system strong.


  1. Cannell J, Vieth R, Umhau J, et al. Epidemic influenza and vitamin D. Epidemiol Infect 2006;134(6):1129-40.
  2. Newall AT, et al. Influenza-related hospitalisation and death in Australians aged 50 years and older. Vaccine 2008;26(17):2135-41.
  3. The Influenza Specialist Group (ISG), Australia. Website: Accessed 1 June 2016.
  4. Sabetta JR, DePetrillo P, Cipriani RJ, et al. Serum 25-hydroxyvitamin d and the incidence of acute viral respiratory tract infections in healthy adults. PLoS One 2010;5:6.


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