This article exists as part of the online archive for HuffPost Australia, which closed in 2021.

What Vitamin D Is, Why You Need It, And How Much

Sand bikini
Sand bikini

The debate on how much vitamin D, including how much we actually need has been topical for some time, with a Deakin University Study of more than 11,000 Australian adults discovering that nearly one third us are suffering vitamin D deficiency.

What is vitamin D, and why do we need it?

“Vitamin D is a hormone and is essential for bone health throughout life but is also important for overall health and well-being,” Dr Michael Holick, Professor of Medicine, Physiology and Biophysics told The Huffington Post Australia.

Vitamin D deficiency has been associated with many chronic and acute illnesses including multiple sclerosis, type 1 diabetes, asthma and wheezing disorders, neurocognitive dysfunction including depression and Alzheimer's disease, among others.

“There is essentially no vitamin D naturally present in the diet -- only oily fish like salmon, cod liver oil and mushrooms that have been exposed to sunlight or artificial sunlight naturally contain vitamin D. The major source of vitamin D is from sensible sun exposure," said Holick.

You’d think that a sun loving country like Australia would have no problems with catching enough rays, though the way vitamin D is produced can also cause confusion.

“There is a misconception about when you can make vitamin D in your skin. You do not absorb vitamin D from the sun but rather you produce vitamin D in the skin during sun exposure. We have demonstrated that essentially no vitamin D3 is produced in the skin before 9 AM and after 4 PM -- even in Australia in the summertime. A sunscreen with an SPF of 30 reduces the capacity of the skin to produce vitamin D by about 98%,” said Holick.

This would indicate we require exposure to the sun during “peak” time without sunscreen, which we've always been told to avoid -- which adds yet another layer of confusion. The good news is, there's an app for that. Dminder gives important information for when and where vitamin D can be produced and also alerts the user when they have made enough -- and to wear sun protection so that they don't get sunburnt.

“Exactly how much sun exposure you need depends on a few things such as where you live, the season, time of day, your skin colour and the amount of skin exposed. I recommend exposure of arms, legs, abdomen and back when appropriate, which the app helps determine,” said Holick.

"However I recommend that you always protect your face from direct sun exposure for two reasons. The first is it’s the most sun exposed and thus most sun damaged, and the second is that it only represents about four percent of your body surface."

An Australian company, Solar D, released a first-to-market range of sunscreens earlier this year that selectively permits vitamin D producing rays to reach the skin to produce vitamin D3.

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