Vitamin D and Immune Health

What is Vitamin D?
Vitamin D is a fat-soluble vitamin produced in the skin during sun exposure. It also comes from dietary sources like fish, fortified foods and supplements when necessary. Whilst vitamin D is known to help absorb calcium and maintain strong bones, its benefits extend beyond the skeletal system. Vitamin D receptors are present on immune cells and known to have a direct effect on immune system regulation. (1)
How Vitamin D supports the Immune System:

• Stimulates antimicrobial peptides- Vitamin D triggers the production of specific peptides called cathelicidin and defensins, which have antiviral and antibacterial properties (2).
• Supports immune cell function- It enhances the performance of T-cells and macrophages, cells that are critical in defending against pathogens (1).
• Reduces inflammation- it helps prevent excessive inflammatory responses, reducing the risk of chronic inflammation (3).

Why Vitamin D Deficiency is Common
Even in areas like Australia known for their sunshine, vitamin D deficiency is still surprisingly common. Factors that contribute include

• Spending more time indoors (especially in winter)
• Aging skin which can reduce vitamin D production
• Chronic health conditions or gut issues that affect absorption.

It is estimated that up to 31% of Australian adults have insufficient vitamin D levels, particularly in winter (4).
Tips for Supporting Vitamin D Levels

1. Get more sunlight – aiming for 10-30 mins a day of sun on the arms and legs, several times per week.
2. Eating Vitamin D rich foods – including salmon, egg yolks, fortified foods including milks and cereals, mushrooms.
3. Consider supplementation- consult your healthcare professional if supplements would be required, especially if a lot of time is spent indoors.

Vitamin D is a critical nutrient for immune resilience, inflammation control and infection prevention. This, combined with regular care, sunshine, good nutrition and stress management should be a key part of your wellness criteria, especially in our colder winter months.
 
References

1. Aranow C. Vitamin D and the immune system. J Investig Med. 2011;59(6):881–886.
2. White JH. Vitamin D signalling, infectious diseases, and regulation of innate immunity. Infect Immun. 2008;76(9):3837–3843.
3. Mora JR, Iwata M, von Andrian UH. Vitamin effects on the immune system: vitamins A and D take centre stage. Nat Rev Immunol. 2008;8(9):685–698.
4. Australian Bureau of Statistics. Vitamin D levels in Australians, 2011–12. ABS Catalogue No. 4364.0.55.006. Canberra: ABS; 2014.