• Amy Donovan BNatMed

You are my sunshine - shedding light on vitamin D

Does vitamin D conjure up thoughts of sunshine for you?

Maybe it's because you remember hearing somewhere about the sun being important in making sure we have enough vitamin D?

Well, you're right!

Our skin holds the remarkable power of transforming the ultraviolet rays from the sun into a vitamin that provides our bodies with enormous benefit.

Just 10-20 minutes of full sun each day provides us with enough 'solar power' to make plenty of our own vitamin D in it's activated form 'calcitriol'

However, what you may not know is that

vitamin D is actually closer to a hormone in it's structure and role in the body.


vitamin D3's scientific name is as it's name suggests - is 'like cholesterol'.

So what does that mean in terms of its roles throughout the body?

Vitamin D's most studied role is in its regulation of calcium absorption

which occurs via the intestines.

It does this by acting as a hormone or messenger in conjunction with

parathyroid hormone to either store calcium in the bones

which can be used to regenerate and remodel them.

Or if calcium blood levels are low due to calcium needs not being met nutritionally, stem cells within bone marrow are given the hurry along to become mature

bone cells in order for stored calcium from the bones to be released.

With vitamin D receptors (VDRs) located ubiquitously throughout the body

this gives us an idea of how extensively vitamin D is used.

VDRs are found in the breast, bone, brain, and endocrine tissue;

as well as cardiac, smooth and skeletal muscle.

Vitamin D plays a crucial role in ensuring bones keep their integrity and don't become weak and porous. Rickets and osteoporosis are two of the main health conditions that can be a result of poor bone mineralisation.

Vitamin D helps to keep your immunity and heart strong,

and greatly assists with skin health and regeneration.

It also plays a role in brain development and mental health,

keeping us mentally sharp and helps to promote positive mood.

How to make sure you are getting enough of the 'D'

New Zealand and Australian nutritional reference values tells us that the 'adequate' intake (because they don't know exactly how much we need)

can sit around 5ug or 200IU/day from birth to around 50 years old,

with requirements increasing slightly from 51 onwards.

To give some perspective on this recommendation,

vitamin D supplements sold here in New Zealand can go up to

1000IU per tablet/capsule.

Food sources of vitamin D are oily fish (sardines, tuna, salmon);

eggs (free-range are always best, for us and the chickens);

and organ meats, particularly liver.

Mushrooms also contain vitamin D2, or ergocalciferol.

Some foods, like milk are now fortified with vitamin D.

However food sources are unlikely to ever give us enough daily vitamin D

adding to the issue that it tends to be poorly absorbed through food.

So we go back to the sun being the best option...

What about being sun smart?

Here in New Zealand we have a dirty big hole in the ozone layer

exposing us to higher levels of 'harmful' UV rays,

so understandably there is a lot of emphasis on the 'Slip, Slop, Slap' approach

to cover up and avoid the harshest sunlight hours in Summer.

However, we do need a certain amount of sunlight exposure to be able to produce this vital vitamin.

Short bursts of sunlight exposure have been studied to be the most effective so this need not mean baking to a crisp in the middle of January!

It is much more beneficial to ensure we have a year round approach

to sun exposure, particularly those of you who have:

- A lower mood/depression

- Seasonal Affective Disorder

- Eczema

- Darker skin (higher melanin means you don't absorb UV rays so well) - Those who wear covering clothing (overalls, hijab, burka)

- Those with 'chalky' bones

Spending at least 20 minutes in the sun (arms, hands, face in Winter)

helps our bodies produce enough of it's own vitamin D, if we give it some help.

Do you need to supplement it?

Some people who are at risk e.g the elderly

may be given vitamin D on prescription by their GP.