Vitamin D – By Tracy Molloy

Why do I need Vitamin D?
Did you know that in Australia just under one in four (23%), or 4 million adults, has a Vitamin D deficiency? 1  Seems strange in a country that has so much good quality food and sunlight….  So what is Vitamin D and why is it so important?

Sun Vitamin D

What is Vitamin D?
Vitamin D refers to a number of cholesterol-like substances including the most important inactive forms:

  • D2ergocalciferol
  • D3cholecalciferol
    which are found in food or produced via exposure to sunlight.

Both D2 and D3 undergo chemical processes in the body that converts them to a more stable Vitamin D, as can be seen below in Figure 1.
Figure 1: The conversion of Inactive Vitamin D to Active Vitamin D 4

Our Vitamin D heads to the liver where this process occurs to form 25-hydroxyvitamin D (25(OH)D) which is the substance measured in our blood to detect our Vitamin D levels.  25(OH) D is then processed again in the kidney to form 1,25(OH)2D, the active form of vitamin D, also known as calcitriol. 3

Why is it important?
Vitamin D plays an important role in a number of processes in the body.  There are Vitamin D receptors (VDR) in many different cells around the body, including skeletal tissue, parathyroid glands as well as reproductive tissues, all of which can receive support from the active Vitamin D.2  Some of the most important  roles it plays in the body, include:

  • Assisting in the absorption of calcium and phosphate which supports bone growth. 5  This is particularly important in children to prevent the development of rickets.  Low levels of Vitamin D can cause low absorption of calcium.  If this happens, triggers within the body will promote the reabsorption into the circulation of calcium from the bones which can lead to softening of the bones or osteomalacia  6 
  • Modulation of the immune system and inhibiting inflammation:
    • Increases antimicrobial peptides which assists with the clearance of bacteria
    • Protects against the development and management of auto-immune diseases, ie Rheumatoid Arthritis, Psoriasis, Multiple Sclerosis
    • Direct effect on T-Cell (Adaptive immune system) activation 7
  • Cell regulation, inhibiting cell proliferation and encouraging apoptosis (programmed death of damaged cells) useful in fighting cancer 8
  • May Increase insulin sensitivity and decrease the risk of metabolic syndrome 9
  • May assist in the stimulation of female and male sex-hormone production 2

Vitamin D and Musculoskeletal health
As mentioned earlier the role of Vitamin D in growing and maintaining strong bones is paramount.  Vitamin D promotes the absorption of calcium into the bone.  If calcium is low the parathyroid gland releases Parathyroid hormone (PTH) which promotes the production of calcitriol from the kidneys.  Calcitriol increases the rate of calcium and phosphorous absorption in the gut.

Vitamin D is also involved in the regulation of osteoblasts and osteoclasts – cells involved in bone growth and development.  Support of this process is vital if there has been any damage to the bone, ie fractures.

Other nutrients required to support bone health include:

  • Magnesium and Boron: important cofactors in the conversion of Vitamin D to its active form
  • Calcium: works with Vitamin D in bone mineralisation
  • Vitamin K: activates Calcitonin also involved in the regulation of calcium and phosphorus
  • Good fats, ie Olive oil: Assists with the absorption of Vitamin D 17

Where do I get it from?
As discussed earlier, Vitamin D comes in 2 forms:

  • D2ergocalciferol – we get approximately 10% from our diet, found in animal products, ie egg yolk and oily fish, ie salmon, mackerel, herring, some plant foods and fungi 2.  Also many foods including milk, orange juice, bread and cereal are fortified with Vitamin D.
  • D3cholecalciferol – 90% is produced in the skin via a precursor substance that, with exposure to UVB light, is converted to cholecalciferol 3

Both are available as supplements. Supplementation is a reasonable alternative to sun exposure, although there is some evidence to suggest that sunlight does provide other benefits beyond Vitamin D production. 16

Vitamin D Foods


How much do I need?
The Australia Government site, National Health and Medical Research Council, (NHMRC) suggests that for adults we need between 5 – 15 mcgs (micrograms) (200 – 600 IUD) depending upon age, as seen in Figure 2.  Keeping in mind, that as we age our ability to synthesise Vitamin D and our exposure to the sun decreases. 10

Figure 2: Recommended Adequate Intake (AI) for Adults 10

Many studies support a healthy maintenance dose of 25 mcg (1,000 IUD). 11  Given the NHMRC suggests the upper limit for Vitamin D is 80 mcg (3,200 IUD) this is well within range and most commonly recommended.


D3 Spray

The BioCeuitcals D3 Spray is available for purchase from bounceREHAB clinics. D3 Spray is preservative free, vegan friendly, peppermint flavoured spray.

So how long in the sun?
Often shorter periods of exposure are more effective than longer periods 12 and exposure time varies depending on skin type, location, season, time of day, cloud coverage. 13  Studies have shown that for an older woman with fair skin, 15-30 mins of exposure to face, arms and hands, 2-3 times a week would provide the daily requirement. 14 Of course in cooler climates with less sun or with darker skin, the exposure time will be more, ie 30 minutes in winter. 15

The best sunshine is mid-morning and afternoon, avoiding the direct heat of the day.  Sunscreen (SPF15) can reduce D3 production by 99% 15.  A balance needs to be struck between appropriate levels of UVB exposure and risk of sun damage to skin.

What if I’m not getting enough Vitamin D?
If you are not getting enough Vitamin D in your diet there are many different forms of Vitamin D available, ie drops, sprays, tablets.  Vitamin D supplements usually contain either vitamin D2 or vitamin D3. Both of these supplements work well in your body and are equally effective.  As Vitamin D is a fat soluble vitamin, it needs to be taken with a meal containing fats to ensure best absorption.   But if you can, avail yourself of nature’s best source – the sunshine!











Tracy Molloy
Bachelor of Health Science
(Nutritional Medicine)
Tracy is bounce REHAB’s guest blogger for June 2015


[1] Australian Health Survey: Biomedical Results for Nutrients, 2011-12. Australian Bureau of Statistics, 2014, Viewed 11th December 2014,

[2] Lerchbaum E and Obermayer-Pietsch B. Vitamin D and fertility: a systematic review, European Journal of Endocrinology,  2012; 166: 765–778

[3] Braun L, Cohen M. Herbs and natural supplements: an evidence-based guide, 3rd ed. Sydney: Churchill Livingstone Elsevier, 2010.

[4] Johnston, L. Sunlight and Vitamin D. ALTERNATIVE & INNOVATIVE THERAPIES FOR PHYSICAL DISABILITY. n.d. Viewed 18th November 2014

[5] Rosen C, Vitamin D supplementation: bones of contention. The Lancet 2014;383:108-109

[6] Wolff A, Jones A, Hansen K. Vitamin D and musculoskeletal health. Nature Clinical Practice Rheumatology. 2008;4(11):580 – 588

[7] Pizzorno J & Murray M. Textbook of Natural Medicine, 4th Ed, Missouri: Elsevier, 2013

[8] Matthew D, Lutz W, Bachman L. Dendritic cell modulation by 1,25 dihydroxyvitamin D3 and its analogs: A Vitamin D receptor-dependant pathway that promotes a persistent state of immaturity in vitro and in vivo. Proceedings of the National Academy of Science, 2001;98(12)

[9] Chiu K, Chu A, Go V, Saad M. Hypovitaminosis D is associated with insulin resistance and B cell dysfunction. American Journal of Clinical Nutrition. 2004;79:820–825

[10] Vitamin D. NHMRC, 2006, Viewed 18th November 2014

[11] Holick M. Vitamin D: importance in the prevention of cancers, type 1 diabetes, heart disease, and osteoporosis. American Journal of Clinical Nutrition. 2004;79:362–71

[12] Working Group (of the Australian and New Zealand Bone and Mineral Society, Endocrine Society of Australia and Osteoporosis Australia). Vitamin D and adult bone health in Australia and New Zealand: a position statement. Medical Journal of Australia. 2005;182:281–285

[13] Vitamin D. Cancer Council of Australia. 2005. Viewed 18th November 2014

[14] Kimlin MG, Downs NJ, Parisi AV. Comparison of human facial UV exposure at high and low latitudes and the potential impact on dermal vitamin D production.  Photochemical & Photobiological Sciences. 2003;2:370-5

[15] Vitamin D and sun protection. Cancer Council of Australia, NSW. 2013 viewed 18th November 2014

[16] Cholecalciferol (Vitamin D). BioCeuticals, NSW. 2013 viewed 18th November 2014

[17] Brody T. Nutritional Biochemistry. San Diego. Academic Press. 1999