This Post is Written In Association With Kinetica Sports


If there is one area of health and wellness that we have become more aware of in the last 18 months, it’s immunity. The resilience of our immune system is central to all aspects of our day-to-day wellbeing. This is true whether we are passionate about getting the most from our fitness training, looking after our mental health, or staying well as we age.

For example, every time we exercise, we stimulate certain pathways that impact our immune system (Nieman and Wentz 2019). How our immune system responds to exercise is determined by the interaction of type, duration, and intensity of that workout, with our pre-existing immune status.

Get it right, and training not only gets us fitter and stronger, but it can also build immune resilience and help us balance inflammation. The opposite is also true. Go above a certain threshold, and training can tax immunity and cause us to become run down (Ribeiro, Petriz et al. 2021). Movement is medicine, but the dosage is important.

Similarly, it has been known for years that the immune system plays a central role in mental health (Dowlati, Herrmann et al. 2010). One of the primary reasons for this is that up to 80% of immune-sensing sensing cells reside in the gastrointestinal tract (Vighi, Marcucci et al. 2008).

The immune system is one of several “motorways” that link the gut to the brain. Information is shared in both directions between the gut and the brain. Research is clear that this gut-brain axis impacts mood in multiple ways.

For example, inflammation in the digestive system caused by excess stress, poor diet and sleep deprivation triggers the release of pro-inflammatory immune messengers called cytokines that impact the brain and predispose us to issues such as anxiety and depression (Petra, Panagiotidou et al. 2015).

In short, immunity is a big deal. It’s central to our physical and mental health and a major advantage in how we feel if we can care for it correctly.

With this in mind, what can do to better look after our immune system?

There are many ways to enhance immune resilience. In this post, we’ll focus on one: optimising vitamin D status.

In this post, we’ll cover the following for you:

  • What is Vitamin D?
  • Where do you get Vitamin D?
  • Why is Vitamin D important?
  • How can one nutrient impact so many physiological systems?
  • How do you measure Vitamin D?
  • What are the normal thresholds for Vitamin D?
  • How can Kinetica’s Vitamin D help you?

Let’s jump in.

The Basics of Vitamin D

What is Vitamin D?

Vitamin D is a fat-soluble vitamin that has local and system-wide effects on the body.  As with other fat-soluble vitamins (A, E and K), vitamin D is absorbed with fats in the diet and stored in the liver and body’s fatty tissue.

Where do you get Vitamin D?

Vitamin D is unique. With other nutrients, our primary method of maintaining healthy levels is through diet. However, in the case of vitamin D, our primary method is sunlight. Up to 90% of vitamin D replenishment comes from sunlight (Chang and Lee 2019).

There are not many foods that naturally contain vitamin D3 (cholecalciferol). Examples include oily fish, egg yolks, shitake mushrooms and organ meats. We can also get a limited amount of vitamin D2 (ergocalciferol) from plant sources. However, sunshine is the key to guaranteeing healthy vitamin D levels. If we cannot get it from solar UVB rays, we may well need supplementation.

For example, the UK is one of the most vitamin D deficient nations in Europe, with nearly 1 in 3 people having deficient levels (Lips, Cashman et al. 2019). As you will find out in a moment, this is a big issue for our health. In contrast, Nordic countries fare much better in vitamin D levels, with recent research estimating that just 0.4-8.4% are vitamin D deficient (Lips, Cashman et al. 2019).

This difference in Vitamin D status is interesting. Both the UK and Nordic countries are similar in that they lack sufficient UVB exposure at certain times of the year. Still, Nordic populations maintain Vitamin D status much better through diet, fortified foods and supplementation.

How is Vitamin D produced?

The body produces vitamin D3 in the skin following exposure to ultraviolet B (UVB) (290–320 nm) radiation from sunlight. There are several steps in the metabolism and bioactivity of vitamin D, from sun exposure to conversion in the liver and kidneys into its active form 1,25(OH)2D (calcitriol) for use in the body.

In the absence of diet and supplementation, several factors can limit our vitamin D levels. Skin colour can be a factor in Vitamin D status, with dark skin pigmentation limiting UVB absorption (Webb, Kazantzidis et al. 2018). Therefore, it is vital for us to regularly check our vitamin D status, especially if we have dark skin, to look after our health.

Sun avoidance, covering the body with clothing, and the use of sunscreen can also be limiting factors in vitamin D status. Interestingly, in my consulting work with PGA Tour and European Tour players, we perform regular bloodwork to understand health and wellness needs. We find that vitamin D deficiency is widespread.

This vitamin D deficiency can seem odd at first sight because golfers live outside in the sun on the golf course. However, they seek to minimise skin damage from ongoing sun exposure by using sunscreen, which can inadvertently lead to vitamin D deficiency. Vitamin D supplementation can therefore play an essential role in their health.

Why is Vitamin D important?

For a long time, we have known about the role of vitamin D in supporting bone health. The active metabolite of vitamin D in the body 1,25(OH)2D promotes intestinal absorption of calcium and phosphorus in the gut. For this reason, vitamin D deficiency is linked with two metabolic bone diseases; rickets in children and osteomalacia in adult (Caccamo, Ricca et al. 2018).

However, there is increasing evidence that vitamin D status is vital for more than skeletal health. The more we learn about Vitamin D, the more we appreciate its role in protecting our health in multiple ways. Vitamin D is central to reducing inflammation, helping to prevent different respiratory illnesses, reducing the severity of Covid-19, and protecting against various chronic diseases, such as cardiovascular disease (Cosentino, Campodonico et al. 2021).

Let’s have a look at these in turn.

How Vitamin D Supports Our Immunity


Inflammation is a natural response by the immune system to different types of insults, such as poor diet, infection, or toxicity. The body is beautifully designed to handle short-term inflammation, and there are multiple lines of defence to help us here.

However, problems occur when those inflammatory processes are not turned off – whether that is due to persistent infection, ongoing toxicity, imbalances in the gut, poor diet, smoking, obesity, excess visceral fat, chronic stress, or the over-generation of reactive oxygen species.

Authors described this challenge of chronic inflammation in a recent paper published in the prestigious journal Nature (Furman, Campisi et al. 2019):

“Chronic inflammatory diseases have been recognized as the most significant cause of death in the world today, with more than 50% of all deaths being attributable to inflammation-related diseases such as ischemic heart disease, stroke, cancer, diabetes mellitus, chronic kidney disease, non-alcoholic fatty liver disease (NAFLD) and autoimmune and neurodegenerative conditions.”

In sum, to live our best, we must learn how to balance the inflammatory load in the body. Vitamin D can help us here.

For example, a recent meta-analysis of randomised controlled trials looked at the effect of vitamin D supplementation on inflammatory markers in those with blood glucose abnormalities (Dashti, Mousavi et al. 2021).

This type of study sits at the top of the evidence-based medicine hierarchy.

The paper included over 3000 participants (n=3099). Results showed that vitamin D administration considerably decreased C-Reactive protein (CRP), a general inflammatory biomarker measured in typical blood tests.

Statistical analysis showed that the probability that this drop in CRP could happen by chance was incredibly low (P < 0.001). We can have confidence that vitamin D can be a tremendous potential intervention tool to reduce inflammation in the body.

One key question then is how? How can vitamin D reduce inflammation in the body? To answer this, we need to look to the immune system. It is now recognised that vitamin D helps to regulate both the innate and adaptive immune system (Bishop, Ismailova et al. 2020).

The innate immune system is our first line of defence. You can think it as legions of marines that are first on the ground helping to combat the enemy – in this case, a bacterial or viral infection. Vitamin D plays a central role in signalling to different parts of the innate immune system, such as monocytes, macrophages, and neutrophils.

These marines flood the area of infection, engulf the enemy and inactivate the pathogen (Hult, Mattila et al. 2021). Vitamin D can also induce apoptosis (death) of cells infected by respiratory pathogens, thereby helping viral clearance (Adams, Ren et al. 2009).

Vitamin D also plays a role in supporting our adaptive immune system (Bishop, Ismailova et al. 2020). The adaptive immune system contains B cells and T cells that help recognise the pathogen for the future and build the specialist forces required to neutralise it upon exposure.

Vitamin D can help create a balanced and tolerant immune response in the adaptive immune system, which is very important. For example, low vitamin D status is linked to a higher risk of autoimmune diseases such as rheumatoid arthritis and irritable bowel disease (Lin, Liu et al. 2016, Khairallah, Makarem et al. 2020).

Respiratory Illness

Given this broad role of vitamin D in supporting immune resilience, it is perhaps no surprise that Vitamin D supplementation is effective in reducing the frequency of upper respiratory tract infections. A recent meta-analysis covering 11,000 participants found that the strongest protection has is in those who had low vitamin D levels, to begin with (Martineau, Jolliffe et al. 2017).

A prospective cohort study in healthy adults showed a two-fold reduction in the risk of developing acute respiratory tract infection in those with serum 25(OH)D levels of 38 ng/mL (95 nmol/L) or more (Sabetta, DePetrillo et al. 2010). We will discuss how to measure and maintain healthy levels of vitamin D in a moment.

Another systematic review of over 5660 patients found that daily vitamin D supplementation had a protective effect against respiratory tract infection (Bergman, Lindh et al. 2013). You can see this in the image below, which shows the pooled effect of different studies:

As we head into winter in Europe and naturally have less access to sunlight, this data clarifies that vitamin D can play an essential role in protecting us against illness.

Vitamin D & Covid-19:

Vitamin D plays a vital role in the fight against Covid-19 too. Multiple studies have looked at the effect of vitamin D status in determining Covid-19 severity and the role that vitamin D might play in treating Covid-19 infection.

Research began to emerge in the summer of 2020, seeking to understand the link between vitamin D and Covid-19. One initial observational study of 185 patients hospitalised in Germany found that 87% of deaths could be attributed to vitamin D deficiency (Brenner and Schottker 2020, Brenner 2021).

Since then, a raft of studies and meta-analyses have come out, and they show a central relationship between Vitamin D status and Covid-19 (Entrenas Castillo, Entrenas Costa et al. 2020, Bayraktar, Turan et al. 2021, Bennouar, Cherif et al. 2021, Borsche, Glauner et al. 2021, Brenner 2021, Liu, Sun et al. 2021, Yisak, Ewunetei et al. 2021).

A key study from Spain found that high-dose vitamin D supplementation significantly reduced the need for intensive-care unit (ICU) treatment (Entrenas Castillo, Entrenas Costa et al. 2020). In other words, vitamin D was both a helpful treatment, and vitamin D status was a predictor of covid-19 severity. You can see a table outlining these results below:

In August of 2021, a study examined why vitamin D status might be linked with Covid-19 outcomes. Results showed that levels of pro-inflammatory cytokines such as IL-1, IL-6 and TNF-a were much higher in the blood of those patients with low levels of vitamin D (Bayraktar, Turan et al. 2021). This correlation makes sense from a physiological standpoint, given that vitamin D exerts anti-inflammatory effects on the body.

These individual studies are supported by more comprehensive systematic reviews, which pool different studies together and weigh up links between vitamin D and Covid-19 based on the quality of the research. An early paper, from December 2020, found that low vitamin D status was a risk for Covid-19 infection (Liu, Sun et al. 2021). This insight is crucial because it alludes to the potential role of vitamin D in prevention rather than just treatment of Covid-19.

In October 2021, a critical systematic review was published, covering nearly 500,000 people worldwide (Borsche, Glauner et al. 2021). It found what is essentially a causal link between vitamin D levels and Covid-19 outcomes. It concluded with several takeaways we can use to help us through the pandemic:

  • Vitamin D status is inversely linked to Covid-19 death rates. This means that when vaccination is not available or possible, those with sufficiently high vitamin D levels preceding infection are highly unlikely to experience fatal outcomes.
  • Given that future mutations of SARS-CoV-2 might evade current vaccines, raising population-level vitamin D status should be a priority. It can help reduce the risk of illness and support overall medical interventions.
  • Vitamin D levels above 30 ng/mL appear to be a key threshold where mortality from Covid-19 decreases considerably.
  • Their analysis shows that vitamin D levels of 50 ng/mL and above might prevent excess mortality at vitamin D levels.

You can see this in the graph below:

This research is incredible. It offers hope and a level of control for so many people with a potentially lifesaving and relatively inexpensive nutrient.

How can Vitamin D impact so many physiological systems?

The first answer to this question is found in the sheer number of vitamin D receptors within us. Vitamin D receptors (known as VDRs) are not just found in a few cells in the body. VDRs are present all over the body: on immune cells, vascular endothelial cells, cardiomyocytes, and more. In this way, vitamin D is regarded less as a nutrient and more like a hormone with actions that impact multiple systems.

In addition to the widespread nature of VDRs, it has been found that vitamin D also influences the expression of more than 2500 different genes in the body (Carlberg 2019). This is amazing. To understand this, think of your genes as an orchestra. Each of us has different genetics, a different orchestral set up if you will. However, as you know, when you listen to beautiful music, not every will instrument play at once. A composer directs the music, with some instruments silent whilst others are in full flow.

In biology, the expression of specific genes and silencing of others throughout your life is called epigenetics. So, your orchestral setup (genetics) is unique, and the expression of specific genes (epigenetics) is unique and based on your lifestyle. Sunshine, diet and supplementation are part of that lifestyle – influencing vitamin D levels and consequently the expression of over 2500 different genes.

How can you check your Vitamin D levels?

Given how vital vitamin D is in your health, you may be curious to know how to measure it. It’s simple. The best indicator of vitamin D status is a blood test that measures 25(OH)D. Vitamin D has a half-life in the body of about 15 days.

What are the normal thresholds for Vitamin D?

There are several different cut-off points for measuring vitamin D, rather than just one. These differences are due to various organisations reviewing literature in a certain way based on the population and geographical area they are interested in looking after.

With that said, research suggests that you can use specific cut-off points to guide your supplementation needs.

Vitamin D Deficiency: Many bodies define risk for vitamin D deficiency as usually 30 nmol/L and most commonly in the 25–30 nmol/L range (Lips, Cashman et al. 2019)

Vitamin D Sufficiency: As you can see from below, different bodies tend to agree that vitamin D sufficiency occurs when levels are in the 50–75 nmol/L range.

How can Kinetica’s Vitamin D help you?

The Institute of Medicine and European Food Safety Authority recommend an upper intake level for vitamin D of 4000 IU/day in adults.

Kinetica’s vitamin D3 comes in an oral spray which makes it easy to take. One spray a day gives you 3000 IU per day. This dose provides peace of mind that you are within upper limits but getting sufficient quantity to support healthy vitamin D levels.

Every Kinetica Vitamin D3 is tested to comply with WADA exacting standards under the Informed-Sport testing regime. Kinetica’s product uses MCT oil as a carrier for Vitamin D for easy absorption. This carrier is essential because, as we mentioned at the start, Vitamin D is a fat-soluble vitamin and therefore needs a carrier to work at its best.

I hope you enjoyed this post, and have a happy and healthy winter 💪

To learn more about Kinetica’s products click here:

Justin Buckthorp, MSc

Justin Buckthorp is the Founder of 360. He has over 20 years of experience in health and wellness and is passionate about improving people's lives.


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