When we think of nutrients that support our immune system health, we typically think of vitamin A, vitamin C and zinc. While each of these nutrients certainly have their place in supporting a healthy immune system response, many others do too – including vitamin D.
We can obtain vitamin D from our diet, through supplementation and also from skin exposure to sunlight. Our vitamin D levels tend to fluctuate throughout the year - we typically have higher vitamin D stores during the warmer months than during winter. Is it a coincidence that, because our vitamin D levels tend to be lower in winter, we get sick more often during the colder months? Let’s find out!
A little intro on Vitamin D
Vitamin D is a fat-soluble vitamin, meaning it is stored in the liver and adipose (fat) tissue when it’s not needed by our cells and organs. It is well known for its role in bone health as it supports the absorption of calcium and the structure of the collagen matrix in our bones.
Upon exposure to sunlight, vitamin D is made in our skin due to a chemical reaction between the sun’s UV rays and cholesterol. Vitamin D then gets absorbed in the blood stream and travels to the liver where it undergoes another reaction to turn into its active form to then be used by the body’s cells and organs.
We can also obtain vitamin D through food and supplementation where it gets absorbed in the small intestine and then travels throughout the blood stream to reach our cells, organs and bones.
A lot of research points to a link between vitamin D deficiency and increased susceptibility to various illnesses and infections, especially upper respiratory infections and autoimmune disease. Keep reading to find out how vitamin D supports a healthy immune system.
How does vitamin D support a healthy immune system?
The human immune system has two lines of defence: the first line of defence is known as our innate immune response and the second is called our adaptive immune response. Vitamin D has the ability to modulate both of these immune system responses - it is required for a number of immune system processes to help defend our cells against pathogens and is a cofactor needed to support our immune cells.
Our innate immune response is fast-acting and short-lived, it helps prevent the spread or movement of pathogens throughout our bodies. Special cells called toll-like receptor cells (TLCs) for example, play a key role in our innate immune response and require vitamin D to activate their potent antimicrobial activity. Other innate immune cells like our macrophages (white blood cells that ‘gobble up’ pathogens and destroy them) also require vitamin D to function at their best.
Our adaptive immune response lasts longer than our innate immune response and involves specific cells creating antibodies against the antigens that pathogens carry. Adaptive immune cells are clever as they remember specific antigens and will be able to trigger faster and stronger immune responses if they come across the same antigen again. Often, our adaptive immune cells produce inflammatory cytokines (small proteins) as a result of their work. Vitamin D’s role is to suppress these inflammatory cytokines which helps to reduce inflammation in the body and further assist with the body’s healing process.
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Vitamin D and autoimmunity
Our immune system is like our body’s own version of the military – it is made up of soldiers (cells) that defend against threatening armies (pathogens). While this is great to help defend foreign pathogens, sometimes things get lost in translation and the immune system starts attacking its own normal body cells. This is known as autoimmunity or autoimmune disease.
Emerging research shows that vitamin D may well play a role in keeping our immune system balanced and that many individuals with diagnosed autoimmune conditions tend to be vitamin D deficient. For example, dendritic cells (immune cells that help to prevent autoimmune damage) depend on vitamin D to mature and proliferate and carry out their protective tasks on our body cells.
Do I need more vitamin D?
Living in sunny Australia, it’s easy to assume that many of us have adequate vitamin D stores. Interestingly, about 1 in 4 Australians are vitamin D deficient! Also, our ability to produce vitamin D from the sun decreases with age, making it a supplement worth taking as we get older.
You can top up your vitamin D stores by:
- exposing your skin to sunlight each day for around 20 mins
- eating foods rich in vitamin D such as egg yolks, oily fish and mushrooms
- taking a vitamin D3 supplement, like our very own Vitamin D3 1000IU or Super Strength Cod Liver Oil 1g
Please seek guidance from your doctor or health professional to determine if you need to increase your vitamin D levels. Do not take any new supplements without consulting a qualified health professional, especially if you have any diagnosed conditions and/or are taking medication.
REFERENCES
Aranow, C. (2011), Vitamin D and the Immune System, Journal of Investigative Medicine, 59(6): 881-886
Bartley, J. (2010), Vitamin D, innate immunity and upper respiratory tract infection, Journal of Laryngology and Otology, 124(5): 465-9
Higdon, J. (2017), Vitamin D, Oregon State University, cited on 24.4.2020, accessed <https://lpi.oregonstate.edu/mic/vitamins/vitamin-D>
Prietl, B. et al. (2013), Vitamin D and Immune Function, Nutrients, 5(7): 2502-2521
