Vitamin D and immunity: What you need to know

Vitamin D and immunity: What you need to know

27 Nov 2021

The human body is delicate and complex, which is why it’s crucial to give it the attention it needs to carry out daily functions, like supporting our immunity. Vitamin D plays a crucial role in our overall health, specifically when it comes to protecting our bodies from illness. Getting your daily dosage of the essential vitamin can help support immune system health.

Nicknamed the “sunshine vitamin,” sufficient levels of vitamin D can be maintained through daily, healthy sun exposure. However, due to the busyness of day-to-day life, this may not be feasible for many Australians. In this case, including a vitamin D supplement as part of a healthy, well-balanced diet can help support your immune system.  

This is particularly important for Australians during seasonal changes, as the immune system may be compromised. Different times of the year bring with them different ailments, with the colder months particularly straining the body’s immune response, making us more susceptible to illness. To help your immune system function optimally all year long, let’s first understand the link between vitamin D and immunity.

How the immune system works

The immune system is a complex network of cells and proteins that defend the body against infection (1). One of these defences works by keeping a track record, so to speak, of every harmful microbe it has ever encountered and successfully fended off. Disease-fighting cells refer to this track record kept by the immune system every time our bodies are alerted to the presence of harmful microbes. In this way, the immune system can quickly recognise and eliminate invaders—especially repeat offenders—that manage to get inside the body and stop them from spreading and doing widespread damage. This mechanism is one of our body’s first, and most effective, defences against all manners of illness.

Vitamin D and immunity

However, there are some illnesses that prove to be more difficult for the immune system to fight off, such as illnesses caused by viruses with different kinds of strains, with each behaving like a new virus that our immune system has had no exposure to. You may have immunity against one strain, yet have no protection against others of the same kind. This is why it is super important to keep our immune system functioning optimally at all times so that we are ready to fend off various types of illnesses.  

When it comes to caring for our immune system so that it can fulfill its health-promoting duties, it’s important that we learn how to keep it robust.

Vitamin D and immunity

Vitamin D is known for its importance in helping the body absorb and retain calcium, which in turn helps keep bones, muscles, and teeth healthy. Only in the last 30 years has it been established that there is a strong link between vitamin D and immunity (2), with the vitamin doing so much more for our health than previously known.

Medical researchers have discovered the presence of vitamin D receptors on the surface of almost all immune cells. To better appreciate this, think of these receptors as locks that can only be opened with the right key. It was found that vitamin D can unlock a response in immune cells and positively influences the activities of our immune system (3), providing immunity-boosting and strengthening benefits. This landmark discovery has spurred several medical inquiries into the interaction of vitamin D and immunity, thus prompting many to focus on the nutrient as part of a healthy diet.

Vitamin D and fending off seasonal ailments

As mentioned earlier, the immune system works continuously throughout the year to protect us from disease, but the wintertime can be particularly stressful on your bodies.  

Vitamin D and immunity

Consider all those times when you or someone you knew was concerned about winter flu, an all too common illness Australians have to deal with come the colder months of the year. Studies have shown that vitamin D is at its lowest levels during the winter season given that it is mostly acquired from the sun’s ultraviolet (UV) rays, and that adults who are vitamin D deficient are more likely to report developing flu symptoms such as a cough, cold, or upper respiratory tract infection (4). Rather than risk getting sick during the winter or any other time of the year, vitamin D can be included into your healthy diet plan as food or supplements.

The best sources of vitamin D

We talked about getting vitamin D from healthy sun exposure, but this essential vitamin can also be acquired from vitamin D-rich foods. You can choose to spend some time outdoors in the sun, but be sure to also eat a well-balanced diet that includes foods such as oily fish (think salmon, sardines, herring, and mackerel), egg yolks, mushroom, and meats (red meat and organ meats, for example) which are all rich in vitamin D (5). Foods fortified with vitamin D include orange juice, dairy products and plant-based milks, and fortified cereals (6).

Vitamin D and immunity

However, it may not always be possible to spend time outdoors or to eat regular meals containing these foods, which is where supplementation comes in. It can be taken alongside a healthy diet to ensure you achieve your daily requirement of vitamin D.

About vitamin D deficiency

If you suspect you have a vitamin D deficiency, there are symptoms to watch out for. You might notice mood fluctuations (with an emphasis on feeling down or blue more often, and for much longer), and general sensations of tiredness or fatigue, and weakness. These might be accompanied by physical pain in your bones, muscles, and joints as well (8), and on top of all this, you may notice that you’ve become more prone to sickness as a result of an immune system that lacks the support it needs from vitamin D (9).

Deciding on a vitamin D supplement

Now that you’re better armed with knowledge about the relationship of vitamin D and immunity, the next step is to assess whether a vitamin D supplement is right for you.

If you’ve ever looked into which vitamin D supplement might suit your needs, you may have learned about the two different kinds; vitamin D2 and vitamin D3. In a nutshell, vitamin D2 is made from plants and is found in fortified foods and some supplements, while vitamin D3 is naturally produced in the human body and is found in animal foods. Both have a role in the relationship between vitamin D and immunity, but vitamin D3 has been cited as the preferred version of the supplement, as it is the variation that’s naturally found in the body.

Vitamin D and immunity

The benefits of a vitamin D supplement

The ultimate advantage of taking a vitamin D supplement is its overall ability to support and maintain optimal immune system function, especially when we are exposed to environmental factors that demand our immunity to work double time. It can also aid in the absorption of other key vitamins and minerals that similarly contribute to the effectiveness of our body’s immune response. In supporting your immune system, you allow yourself to enjoy living a full life that is not weighed down by illness.

Making sure you’re getting the right amount of vitamin D is pretty easy when you subscribe to Vitable Australia. It’s even easier when you sign up for our monthly vitamin subscription programme where the best vitamin packs are only a matter of clicks away. You also get to curate your personalised vitamin packs based on your unique health needs, which will be sent right to your doorstep via our vitamin delivery service.

Find out more about other supplements that can help you with immunity:

Zinc | Iron | Astaxanthin | Ashwagandha | Probiotics SB | B complex | Vitamin C | Vitamin D | Daily probiotics | Vitamin B12 | Fish oil | Biotin

*Always read the label. Follow the directions for use. If symptoms persist, talk to your health professional. Vitamin and/or mineral supplements should not replace a balanced diet.


  1. Better Health. "Immune system explained." Better Health. Published (n.d.) on . Accessed 15 October 2021.
  2. Hewlson, Martin. "Vitamin D and immune function: an overview." Cambridge University Press. Published 18 August 2011 on . Accessed 15 October 2021.
  3. NPS Medicinewise. "Vitamin D and COVID-19." NPS Medicinewise. Published 3 August 2020 on . Accessed 15 October 2021.
  4. Harvard School of Public Health. "Vitamin D." Harvard School of Public Health. Published (n.d.) on . Accessed 15 October 2021.
  5. NPS Medicinewise. "Vitamin D and COVID-19." NPS Medicinewise. Published 3 August 2020 on . Accessed 15 October 2021.
  6. Health Direct. "Vitamin D deficiency." Health Direct. Published (n.d.) on . Accessed 17 October 2021.
  7. Harvard School of Public Health. "Vitamin D." Harvard School of Public Health. Published (n.d.) on . Accessed 15 October 2021.
  8. Cleveland Clinic. "Vitamin D Deficiency.” n.d. Accessed 20 October 2021.
  9. Health Direct. "Vitamin D deficiency." Health Direct. Published (n.d.) on . Accessed 17 October 2021.