A quick recap - vitamin D is made in your body from direct sun exposure on your skin. There are many factors needed for this to occur, such as sufficient cholesterol levels, good liver and kidney function and more.
Vitamin D production is also dependent on your location, or distance from the equator. The further you are from the equator, especially in winter, the more time you need to spend in the sun to make sufficient vitamin D. In summer, the amount of time you need to spend in the sun in most capital cities in Australia to make the same amount of vitamin D is similar (at 6-9 mins daily, as shown in the attached table). In winter, however, the differences between the capital cities are very different. Much more time is needed in winter to make the same amount of vitamin D, at 9-12 minutes for northern cities, or up to 52 minutes daily in southern cities such as Melbourne (Diamond et al., 2005). Spending an hour outside in Melbourne in shorts and t-shirt every day in winter isn't going to happen!
Those at high risk of vitamin D deficiency include the elderly, who we have seen in the coronavirus pandemic have had the greatest loss of life, those in aged care and hospital, shift workers, mothers with breastfed infants, and those with darker skin who need 3-4 times this sun exposure to get the same vitamin D levels (Diamond et al., 2005).
Vitamin D acts as an anti-inflammatory hormone in your body, to reduce inflammation, as well as being a massive immune system booster (Prietl, Treiber, Pieber & Amrein, 2013) and prevention of most respiratory infections such as the common cold, flu (Fagbo et al. 2017), and even the new coronavirus (Grant et al., 2020). Normally, your vitamin D levels should be high through summer from the warmer weather and sun exposure, and high enough to keep your levels sufficient through the colder months. But sun-safe programs of avoiding the sun and wearing sunscreens reduce or even prevent the production of vitamin D, which explains why most people do not have enough of the preventative benefits of vitamin D. It is well known in published studies that a low vitamin D level in winter increases your risk of any respiratory infection.
I was not surprised when the coronavirus outbreak and pandemic occurred in the northern hemisphere during and immediately after their winter, being their highest risk period of low vitamin D levels. Southern hemisphere countries, such as here in Australia, were mostly protected as we were coming out of summer and when vitamin D levels are highest.
But now, being in the period of lowest vitamin D levels in Australia, this is the time of highest risk, but also the most critical time to prevent and reduce incidences of flu and the coronavirus, by addressing the major cause of respiratory infections and a low immune system function - by checking and improving your vitamin D levels.
You can get your vitamin D levels checked with a quick blood test. This can be requested through your GP, or even through me! Vitamin D testing is a paid-for test, at about $30 (ex GST) to the lab at the time of the test.
What result should you look for? In Australia, optimal vitamin D levels need to be at a minimum of 100 nmol/L. Other countries use different units of measurement, so your result may need to be converted.
If you are supplementing with vitamin D through winter or as a preventative for the coronavirus, GREAT! The dose is important too, more so if you have low levels. Therapeutic doses require a minimum of 3000-5000IU per day for adults for at least 6 weeks (Diamond et al., 2005), in order to increase your levels and get health benefits.
There are other factors which can reduce your vitamin D levels, which may need to be investigated and treated, in order to improve your results.
If you are in winter and further from the equator (NB, especially those in Victoria!) get onto the above high dose vitamin D supplementation to reduce your risks of the coronavirus, reduce incidences and mortality, and be able to get back to your free lives again!
Diamond, T.H., Eisman, J.A., Mason, R.S., Nowson, C.A., Pasco, J.A., Sambrook, P.N., & Wark, J.D. (2005). Vitamin D and adult bone health in Australia and New Zealand: a position statement. Medical Journal of Australia, 182 (6), 281-285. doi: 10.5694/j.1326-5377.2005.tb06701.x
Fagbo, S.F., Garbati, M.A., Hasan, R., AlShahrani, D., Al-Shehri, M., AlFawaz, T., Hakawi, A., Wani, T.A., Skakni, L. (2017). Acute viral respiratory infections among children in MERS-endemic Riyadh, Saudi Arabia, 2012-2013. Journal of Medical Virology, 89 (2):195-201. doi: 10.1002/jmv.24632
Grant, W.B., Lahore, H., McDonnell, S.L., Baggerly, C.A., French, C.B., Aliano, J.L., & Bhattoa, H.P. (2020). Evidence that Vitamin D Supplementation Could Reduce Risk of Influenza and COVID-19 Infections and Deaths. Nutrients, 12 (4), 988. Doi: 10.3390/nu12040988
Prietl, B., Treiber, G., Pieber, T.R., & Amrein, K. (2013). Vitamin D and Immune Function. Nutrients, 5 (7): 2502–2521. doi: 10.3390/nu5072502