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Nutrition

How does vitamin D support immune system health?

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Written by Dr Jane Winter
Sunlight Vitamin D

What is vitamin D?

Vitamin D was discovered nearly 100 years ago and as it was the fourth 'vitamin' discovered, it was named vitamin D. Scientists found that sunshine provided the same benefits to bone health[1] and that the same compound could be manufactured by the skin or obtained from some dietary sources.

Vitamin D is present in two forms: vitamin D2 (present in foods) and vitamin D3, which forms in the skin when it is exposed to UV rays from the sun. It is then transported to the liver and finally the kidneys where it is activated to enable it to play its role in our bodies. Vitamin D plays a critical role in maintaining strong, healthy bones. However, this vitamin isn’t just essential for bone health. Research also shows that it plays a vital role in maintaining a healthy immune system.

How does vitamin D help support immune health and function?

Well, it’s essential for creating the antimicrobial proteins in the body, which are important in our immune defence system. Vitamin D also reduces inflammation in the body and strengthens the barrier function of the epithelial cells (cells that act as a barrier between the inside and outside of your body)[1].

What does the research tell us about vitamin D?

Research shows that a lack of sufficient vitamin D may lead to a weakened immune system, as vitamin D modulates the cells needed for the immune response1.

Are you getting enough vitamin D?

The potential risk of vitamin D deficiency not only includes a compromised immune system, but also a loss of bone density.

With vitamin D being generated mainly through exposure to sunlight, getting enough of it in NZ is easy enough.

How you can help your body to meet vitamin D intake requirements

90% of our vitamin D intake is made directly from sunlight exposure[3], with national guidelines[4] recommending at least a few minutes of sun exposure each day. So, if it’s possible to get out on a balcony or briefly exercise outdoors, this can help support your body in achieving its daily dose.

In order to reap the vitamin D-boosting benefits of sunlight, your bare skin must come into direct contact.

The other 10% of our vitamin D intake comes from dietary sources2. An adequate dietary intake of vitamin D has been set at 5-10 micrograms per day (or 200-400 IU) However, it's estimated that most adults only get 2-3 micrograms per day from their diet.

Food sources of vitamin D include:

  • Fatty fish such as salmon, tuna, and mackerel
  • Liver
  • UV irradiated Mushrooms
  • Egg yolks.

Foods fortified with vitamin D include:

  • Milk
  • Breakfast cereals
  • Other dairy products, such as yoghurt
  • Soy drinks.

Be sure to check the label to determine whether it has been fortified with vitamin D.

That said, increasing vitamin D levels through diet alone is very difficult. So, in times where sun exposure is minimal vitamin D supplementation can be a great option for further support. Vitamin D of at least 600 IU (15 µg) per day for adults is recommended[5].

References:

[1] Sassi F et al. Nutrients 2018;10:1656-69

[3] Nowson C et al. Med J Aust 2012; 196 (11): 686-687

[4] https://www.cancer.org.au/preventing-cancer/sun-protection/vitamin-d/

[5] Nowson C et al Med J Aust 2012; 196 (11): 686-687