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Vitamin D: Why It Matters for Your Immune Health

Vitamin D: Why It Matters for Your Immune Health

, by AussiePharmaDirect, 7 min reading time

Have you ever heard people say, "It's good to be out in the sun once in a while, it's good for your health"? Well, they're onto something! 

One of the key reasons why sunlight is beneficial is because it helps our bodies produce a special vitamin called vitamin D. Vitamin D is often referred to as the "sunshine vitamin" because our bodies can synthesise it when our skin is exposed to sunlight, and this plays a crucial role in our health.

Most importantly, it has a significant correlation with our immune system. Adequate levels of vitamin D have been linked to a well-functioning immune system.

So, what exactly is vitamin D for, how does it help with our overall well-being, and what are other sources besides the sun that you can get vitamin D from? We’ll cover these and some other common questions about vitamin D as a source of nutrients in this blog.

Vitamin D benefits at a glance

Before we dive into the nitty gritty details of vitamin D's role in the immune system, let's take a step back and explore the wide-ranging impacts this remarkable nutrient has in various areas of our physiology.

  • Promoting strong and healthy bones
  • Enhanced muscle function
  • Immune system regulation
  • May improve mood and mental well-being (research indicates that adequate vitamin D levels may be associated with a reduced risk of depression, seasonal affective disorder (SAD), and cognitive decline
  • Reduced risk of cardiovascular condition (based on a study but further research is needed to establish a definitive cause-and-effect relationship
  • Cancer prevention (several studies suggest vitamin D's potential anticancer but research in this area is still ongoing)
  • Autoimmune disease management

How does vitamin D help the immune system?

Here are some key ways in which vitamin D aids the immune system:

  • Vitamin D helps regulate the function of various immune cells, including T cells, B cells, and macrophages. It promotes the maturation and differentiation of these cells, enhancing their ability to recognise and respond to pathogens effectively. 
  • It enhances the production of antimicrobial peptides (AMPs) in immune cells, that help protect against invading microorganisms by disrupting the integrity of microbial cell membranes.
  • It helps maintain a balanced inflammatory response. It can modulate the production of pro-inflammatory cytokines, such as interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-alpha), preventing excessive inflammation.
  • Vitamin D has been implicated in the development and progression of autoimmune diseases. It is believed that vitamin D helps regulate immune cell activity and reduce the production of autoantibodies.
  • Vitamin D helps maintain the structural integrity of epithelial barriers, enhances their antimicrobial properties, and supports their ability to prevent the entry and spread of pathogens.

Sources of vitamin D

While sunlight is a natural and important source of vitamin D, it's crucial to strike a balance and be mindful of potential adverse effects associated with excessive sun exposure such as skin damage, premature aging, increased risk of skin cancer, and even eye damage.

But fret not! In addition to sunlight, there are alternative ways to ensure an adequate intake of vitamin D, and they’re through dietary sources and supplements. 

1. Dietary sources

  • Fatty fish - Salmon, mackerel, sardines, and trout are excellent natural sources of vitamin D, particularly vitamin D3
  • Cod liver oil - This oil derived from the liver of codfish is rich in vitamin D3 and has been traditionally used as a vitamin D supplement
  • Fortified foods - Many food products are fortified with vitamin D, such as milk, orange juice, breakfast cereals, and dairy alternatives like soy or almond milk
  • Egg yolks - Contain small amounts of vitamin D

2. Supplements

When natural dietary sources and sunlight exposure are insufficient, vitamin D supplements can be an effective option too. For vitamin D, there are two main forms available: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). While both forms can raise vitamin D levels in the body, there are some differences between them.

But when it comes to supporting immune health, the type of vitamin D that is more effective is vitamin D3. Vitamin D3 has been recognised for its potential to bolster the immune system more effectively compared to vitamin D2.

What should be the normal vitamin D levels?

Did you know that different countries can have different ideas about what constitutes normal or optimal vitamin D levels? These variations are often influenced by factors such as geographical location, climate, sunlight exposure, and the specific recommendations of national health organisations.

In Australia, the reference range for normal vitamin D levels is typically measured in nanomoles per litre (nmol/L). The guidelines for vitamin D levels in Australia from both Healthy Bones Australia and The Royal College of Pathologists of Australasia (RCPA) are as follows:

  • Vitamin D deficiency: Less than 50 nmol/L
  • Vitamin D insufficiency: 50-75 nmol/L
  • Adequate vitamin D levels: 75-250 nmol/L

If you're curious about your vitamin D levels, a vitamin D blood test is the most common and reliable way to assess your status. Getting a vitamin D blood test is generally an accessible and straightforward process, and in Australia, vitamin D blood tests are commonly available at clinics, diagnostic centres, and laboratories.

How much vitamin D per day to boost your immune system?

According to the Royal Australian College of General Practitioners (RACGP), the recommended daily intake of vitamin D for immune health can vary depending on age and individual circumstances:

  • Infants (0-12 months): An average daily intake of 400-1,000 international units (IU) of Vitamin D
  • Children and adults (1-70 years): A daily intake of 600-1,000 IU of vitamin D
  • Adults over 70 years: Adults over the age of 70 are at a higher risk of vitamin D deficiency and may require higher intake to maintain adequate levels - A daily intake of 800-2,000 IU of vitamin D

It is important to ensure adequate vitamin D levels to support overall well-being. Unfortunately, vitamin D deficiency is a common issue, particularly in Australia where about 1 in 4 Australians have a vitamin D deficiency. To combat vitamin D deficiency, it is recommended to incorporate strategies such as safe sun exposure, consuming foods rich in vitamin D, and considering vitamin D supplementation when necessary. If you suspect that might be low in vitamin D, it is also crucial to be aware of the signs and symptoms of vitamin D deficiency as early detection can help address the issue promptly.


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