Vitamin D - Everything you ever wanted to know (probably)

Most of us are aware of the existence of vitamin D and that it’s got something to do with the sun. That’s probably about it. The vitamin D/sun relationship is actually a little more complicated, and whether you’re getting enough of it is dependent on more factors than managing to leave the office at lunchtime. The level of air pollution, skin pigmentation,  geographic location, season and presence of (or lack thereof) clothing and sunscreen all affect our vitamin D status.

What’s super cool about the importance of vitamin D is that it supports the idea that for good health, humans need to spend time outdoors, in nature, under the sun. Simple, but a concept that has been lost in our busy modern lives.

A crash course in understanding vitamin D 

The conversion of UVB rays to active vitamin D resembles a cross between year 11 chemistry and a train line.

We literally need to be exposed to the sun’s warm, life-giving rays to convert the UVB light to pre-vitamin D, a process that happens on our outermost layer – the skin (train tracks). This is called photolysis. From here, pre-vitamin D is bound to a special transport protein (train) which delivers the pre-vitamin D (cargo) to the liver. In the liver, our pre-vitamin D is converted via hydroxylation and takes the form of calcidiol or ’25(OH)D’. This is the vitamin D that is circulated in the blood and which is tested for by your GP. “Then what?” I hear you ask on the edge of your seat? Well the chemistry lesson continues, because 25(OH)D has to be activated by bodily tissues in order for it to be of any use. The 25(OH)D delivered to the organs such as the brain, kidneys, heart, immune cells and breast tissue is turned into 1,25(OH)²D. Active vitamin D. The amount that the kidneys can produce may be different to other organs, because other cofactors that might be required are available at differing amounts. We won’t go there today.

So once our tissues have this activated vitamin D, what do they do with it? There is one last piece to this vitamin D. Now that we have our tracks and our train, the vitamin D needs a station – vitamin D receptors (VDR) which the D can bind to in order to be distributed locally, for gene expression, cell communication, enzyme production and other physiological processes that allow our bodies to function optimally.

Vitamin D deficiency – 25(OH)D levels less than 20nmol/mL

The role of vitamin D in the human body is still being researched, however we do know vitamin D is ultra-important for bone health such as preventing osteoporosis, by assisting the absorption of calcium. Osteoporosis due to loss of bone density is something we associate with the elderly, however building healthy bone density occurs mostly during our 20’s. After this, bone density is on the decrease. Researchers are also looking into the role of vitamin D in the prevention and treatment of:

  • Multiple sclerosis (MS) and other autoimmune disease

  • Depression and mood disorders including seasonal affective disorder (SAD)*

  • Cancer (17 various types including breast cancer)

  • Diabetes

  • Influenza and other viral infections

  • Fertility and gynacological health

Whilst the reference range for 25(OH)D is highly debated, at present it is 20-100nmol/mL.

Some experts suggest that optimal 25(OH)D is 60-90nmol/mL and that the reference range should be updated to prevent deficiency being mis-interpreted as ‘within range’ and therefore of no clinical effect.

*ever noticed changes to your happiness with the seasons? Felt SAD in gloomy winter?

Give me the D!

Another commonly unknown factor about Vitamin D absorption is the lattitude hypothesis – the idea that your ability to produce vitamin D from the sun may be different to your cousin in London or even your neighbour. Put simply, your geographical location, the date on the calendar and the pigmentation of your skin all affect how much time you need in the sun to make maintain adequate levels of vitamin D. One of the coolest (nerdiest) things I have found on the internet is a calculator by the Norwegian Institute for Air Research that will give you the estimated amount of time in the sun you need, on any given day, anywhere on earth, to produce the equivalent of 25ug of vitamin D. Simply Google the longitude, latitude, elevation of your geographic location, enter a few other specific parameters and away you go!

Click here to calculate your required sun exposure

For me with my extremely fair skin, in my home town of Mooroolbark, VIC, on today the 2nd of Feb, on a cloudless day at midday, I need about 2 minutes in the sun. In the same conditions in July, I need about 12 minutes. My doppelganger in London would be requiring about 44 minutes right now. Hours of fun!

So get outside regularly, soak up the sunshine and feel your skin busily working to improve your health.

Alexandra McPhee