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Vitamin D and the Immune System

by Jade Newton |

It’s that time of year again. The jumpers are being layered, our lips are constantly chapped no matter how much lip balm we apply, and throat sweets are being devoured as quickly as pick’n’mix. All of which we can thank the increase in coughs and colds for. But why is it that this time of year always brings with it a myriad of different maladies for us to battle our way through?

Research suggests that one reason for the increase in bugs is due to the cold, dry air, as certain viruses travel more easily in this climate [1]. However another possibility for this increase, is the typical corresponding decrease in vitamin D that begins once the clocks have gone back.

Vitamin D is known predominantly for it's ability to help strengthen bones, however Cynthia Anarow explains to us [2] that "Vitamin D has important functions beyond those of calcium and bone homeostasis which include modulation of the innate and adaptive immune responses." Simply put, she tells us that vitamin D plays an important role in keeping the immune system on top form. This is furthered by the Vitamin D Council who explain that low levels of this vitamin can lead to the immune system not functioning correctly, as less natural-occurring antibiotics are released and kill less of the invading bacteria. So how do we ensure our vitamin D  levels are maintained during the winter to keep our immune system functioning to the best of it's ability?

Let's be honest, we all need more vitamin D in our lives.


As a nation, thanks to the social strains of office jobs and other responsibilities pulling us indoors and away from the sun, we are generally vitamin D deficient.

During the summer it's very simple to resolve this nationwide deficiency: the more time you spend in the sun, the more vitamin D in you will produce and the healthier your immune system will be. However as we start the slog through the winter months, this can be a bit more difficult; sunlight between October and March is too weak to contain enough UVB for our skin to replenish our vitamin D stores [3]. So how can we keep our vitamin D levels stable this winter and lessen the likelihood of picking up as many bugs?

Well, there are three main ways of sourcing vitamin D:

1. Diet

2. Supplements

3. UV exposure [4].

According to the NHS, it's difficult to get enough vitamin D from food alone, and so to solve this, many resort to supplements [5]. However supplements cannot be stored in the body long-term. These can also lead to an overdose of vitamin D - Where lacking in this vitamin can be harmful, so can having too much [6]. An overdose of vitamin D can raise the levels of calcium in the blood and affect your heart negatively. 

Sissons claims that unlike with supplements, "it is not possible for the body to make too much vitamin D from sun exposure." [6]


The most effective way of absorbing vitamin D is through UV exposure. 

UV light reacts with your skin, creating The Sunshine Vitamin and keeping the immune system healthy. By gaining vitamin D from UV light, your body is able to store it long term, meaning that unlike supplements, this doesn't have to be sought after daily. What's more, unlike supplements, your body is unable to overdose on vitamin D created by UV.

As previously stated, it's clear that UV is easier to absorb in the summer, however that doesn't mean it isn't feasible during the winter months. Although you are unable to gain vitamin D outdoors at this time of year, the use of sunbeds may improve vitamin D levels*. Although the source of light in tanning booths is artificial, the UV produced is not. What's more, sunbeds can offer a much more personalised tanning experience than sunlight. When tanning outdoors, the time spent is uncontrolled and if not careful, can lead to overexposed skin and burning. Sunbeds allow tanners to control their time, minimising the risk of burning and maximising the tanning and vitamin D absorption [7].

So grab the lemsip, keep hydrated and get that early night. But don't forget to still get that UV boost to keep your vitamin D levels stable and help your immune system help you. Rather than googling your symptoms, it may just be that you need a ten minute holiday!


* Please note that by sunbeds, we refer to sunbeds which adhere to EU 0.3 regulations. Simply put, this means that the lamps used in the beds (dubbed '0.3') are the equivalent of the midday Mediterranean sun. Sunbeds adhering to these standards will offer not only a more relaxing tanning experience, but a deeper tan that lasts even longer and a lesser likelihood of overexposing skin and burning. Always tan for your skin type. Don't overexpose and never allow yourself to burn. Always wear eye protection ☀️