education,  nutrition

Vitamin D: the sunshine nutrient.

Well, we’ve done the basics of micronutrients (carbohydrates, protein & fat) so now we’re ready to start with micronutrients. These are basically vitamins, minerals, electrolytes & water. I’ll be going over these slowly over the next few months. Given that we are changing seasons the world over I thought I’d start with Vitamin D since this one has a lot to do with the weather!

Vitamin D is an umbrella term for 2 molecules. Vitamin D2 (egrocalciferol), & Vitamin D3 (cholecalciferol). You may have seen these names on supplement packaging.

Vitamin D2 is consumed via plant sources while Vitamin D3 is synthesised in the skin (subcutaneous production). That’s right people, your skin can make its own D3!

Now, I’m not going to go too much into the chemistry behind it (let me know if you’d be interested in this by the way). Instead I’m just going to give you the basics.


What does it do?

Vitamin D plays a crucial role in regulating calcium levels in our bones, intestines & kidneys.

It can build or break down bones depending on the calcium levels in our body.

It is also involved in cell growth, neuromuscular & immune function & in the reduction of inflammation.


Vitamin D3, how do we make it exactly?

Sunlight! This is why it’s got to do with the seasons. When the sun hits our skin our bodies jump to action & start making vitamin D3. This is great in summer but a little harder in winter.

It also depends on where you are on the planet, cloud cover, time & length of the day, pollution, what sun-screening techniques you use & just how much time you spend in direct sunlight.




It’s assumed that Australians receive enough exposure to sunlight to supply their daily needs. Unfortunately this isn’t true in all cases & supplementation is recommended. For instance, I live in Tasmania, the little island state right at the bottom of Australia (often cut off in maps) where the sun doesn’t hit us at the right angle for vitamin D synthesis. Studies have found that as latitude increases, that amount of vitamin D UV decreases which significantly decreases synthesis.

We in Tasmania have the double whammy of being under the hole in the ozone layer which means we really can’t leave the house for any extended period of time without being burnt to a crisp. As a result we use a lot of sun protection which of course decreases our skins UV exposure thus decreasing our VD synthesis. Evidence also shows that as latitude increases so do the health conditions associated with VD deficiency (lucky us!)


Dietary Sources

Animal products such as oily fish, full-fat butter & cheese, liver & eggs.

While meat & other dairy do contain vitamin D, the amount is comparatively small.


You can often find products that have been fortified with VD – margarines are a fairly well-known one in Australia. In the US the majority of milk is voluntarily fortified with Vitamin D.



Fortunately, we have access to supplementation so we can keep our supplies topped up when we can’t get out in the sun.


If you live nearer the poles, a daily dose of 1000 IU (International Units) of vitamin D3 is sufficient to see you through the colder months or those months when you stay out the sun. If you’re close to the equator it’s unlikely you’ll need supplementation even in winter.


Deficiency: am I at risk?

Likelihood of deficiency results from insufficient supply of dietary VD, or an inability to synthesis adequate amounts. Groups most at risk of inadequate VD are babies breastfed by deficient mothers, older adults, people who for whatever reasons have very limited exposure to the sun. People who have higher levels of melanin in the skin (pigment), people with conditions causing malabsorption such as inflammatory bowel disease, obese people, & those who have had gastric banding are also at increased risk.

Deficiency of this important vitamin D as it leads to developmental delays & damage to all systems involved. It leads to bone loss & osteomalacia which is a precursor to osteoporosis.

Children are more at risk for deficiency resulting in rickets – a bone condition causing shortening & extreme bowing of the legs due to the weight of the child putting pressure on soft bones that are still developing. A child suffering deficiency will usually experience growth & developmental delays. There is also some evidence that VD is involved in the immune system as infections are more common in those with deficiency.

In extreme cases of deficiency, there isn’t enough calcium in the blood which can result in convulsions & even death.

Increases risk of Osteoporosis, Seasonal Affective Disorder (SAD), Schizophrenia & Depression

There is some emerging evidence suggesting deficiency may be associated with some cancers. Diabetes, glucose intolerance, hypertension & Multiple sclerosis.

More research needed to confirm these relationships though.


Is there such a thing as too much?

Vitamin D is stored in body fat so it is possible to reach levels of toxicity (where it becomes toxic to the person).

Symptoms of toxicity include calcification (hardening) or soft tissues, most often affecting the kidney & the arterial walls.

In children excessive VD causes the bones to harden prematurely and stunts growth.

Don’t stress though, toxicity is very rare & it’s likely you’ll never have to worry about it. There have been studies which have shown that supplementing the body with high doses of vitamin D have not caused any detrimental effects. This was in a controlled, experimental situation which was closely observed so under no circumstances would I recommend self-supplementation of high doses of VD. In any case it really isn’t necessary.


No need to panic.

If you’re not sure whether you need supplementation & (wisely) don’t want to take supplements without cause, your GP can find out if you are deficient through a simple blood test. From there it’s easy to find the right supplement for you!

That’s it, a quick introduction to this really important vitamin. If you would like me to write a more detailed post please let me know.

If you’d like to find out more, check out some useful references here & here.

Would personalised one-on-one consultations with me help you master your diet &/or weight? If the answer is yes then send me an email using the contact form below & we’ll arrange a call or Skype.

Did you find this post useful?

Do you have any questions or anything else to add?

Please leave a comment or send me an email, I’d love to hear from you.

I’d also love to know what you’d like to see in future posts. If you’d like me to write about something in particular, please let me know.

Thankyou so much for joining me for this post.

Happy reading!



Kathryn Carter

I’m Kath, qualified nutritionist & personal trainer. I believe a personalised, flexibile approach to gaining physical & mental well-being is necessary for achieving sustainable lifestyle changes that support both these aspects of health. In the near future I will be offering a range of nutrition & lifestyle education services designed to gain the life my clients want in a way that works for them.

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