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12th December 2023

Vitamin D - The Sunshine Superhero

By Dr Daniel Owens, PhD SENr

6 Minute Read

Every Autumn we hear about getting enough vitamin D. But have you ever wondered about the magic behind vitamin D, often dubbed the 'Sunshine Vitamin'?

Let's dive into why it's highly beneficial for your health and performance, and some easy steps you can take to maintain your vitamin D levels year-round.

Why Vitamin D Matters

Vitamin D isn't just another supplement; our body has a requirement for it since it cannot be made within the body. It's a key player for your bones, muscles, and immune system.

Most of our vitamin D comes from exposing the skin to sunlight (around 80-90% of our requirement), with a small portion from our diet from sources like oily fish and dairy products.

However, many people, especially during those gloomy Winter months, find themselves lacking this vital nutrient because sunlight exposure is limited.

It's estimated that 40% of people in Europe have vitamin D deficiency (Cashman, 2020), but it's a simple fix that can have important outcomes for your health and performance. 


Vitamin D Metabolism Simplified

Here's a quick breakdown of how vitamin D is obtained and works in your body.

Ultraviolet B (UVB) radiation from sunlight converts a substance in your skin into Vitamin D3, or you may eat some vitamin D containing foods or a supplement. Whichever way you get the vitamin D, it then travels through your bloodstream to your liver and kidneys, turning into the active form your body can use. This process is vital for regulating bone health, immune function, muscle repair and metabolism. 


Understanding Vitamin D Levels

Measuring vitamin D can be tricky since it requires a blood test and often isn’t cheap. Moreover, people from different ethnic backgrounds may show variations in vitamin D levels, and the current science suggests there may not be a one-size-fits-all method to assess an individuals vitamin D status. However, if you do get a vitamin D blood test, current science recommends a blood level of above 75 nmol/L is sufficient. 

We understand that blood tests are not always accessible, so let’s take a look at the risk factors, which can help you determine if you might have low vitamin D levels. 

Any factors that limit sun exposure are likely to have the biggest effect on our vitamin D levels. Indoor living and working, covering up the skin year-round with clothing, using high-factor sunscreen year-round, cloud cover, and season of the  year are the main risk factors (Chen et al., 2007). Even if the sun is out during the Winter, you won’t be making vitamin D in your skin, since the sun is too low in the sky and not enough of its UVB actually makes it to the earths surface (and therefore your skin!).


The Importance of Vitamin D for Active Individuals

Maintaining a good vitamin D status (>75 nmol/L) is crucial for bone health, muscle function, and immune support.

With chronically low vitamin D levels, we see weaker bones that are more susceptible to fracture. Muscle function and metabolism can be impaired meaning potentially sub-optimal adaptation to your training, and a significant increase in your susceptibility to infection. What’s more, when vitamin D levels are low the severity of those infections and the length of time you have symptoms for can worsen.

However, it's not about trying to ramp up your vitamin D levels as high as you can, but rather avoiding deficiencies and trying to keep your levels  above 75 nmol/L year round.

More is not better with vitamin D and the focus should be on getting your level of vitamin D into the normal range rather than trying to mega boost your levels.

In the Summer months, safe sun exposure (avoiding burning) is typically enough to maintain sufficient status. However, during Winter this is rarely achievable and a supplementation strategy is often required.

  • For people with lighter skin, daily sunlight exposure of unprotected skin for 10-15 minutes during the spring and summer months will avoid vitamin D deficiency. For most, this will be a relatively safe level of exposure, balancing the benefits of vitamin D and minimising the risks of skin cancer. This should be undertaken in the middle of the day, with exposure of lower arms and lower legs to maximise benefit. Vitamin D supplements are advisable during the winter months to maintain vitamin D levels.
  • For people with darker skin, 25-40 minutes of exposure under the same conditions will avoid Summertime vitamin D deficiency, and vitamin D supplements are also advisable during the winter months.

Smart Supplementation

Firstly, the type of vitamin D matters and with the minefield of supplements out there, we’re here to help you make the best choice. 

Vitamin D3 is more effective than Vitamin D2 and should be the type of vitamin D supplement you opt for. But remember the golden rule: moderation is key. A daily dose of 1000-2000 IU is usually sufficient and there are plenty of supplements out there containing 5x as much as this, which simply isn’t necessary. It’s estimated that this intake of 1000-2000 IU/day is what most of the adult population require to maintain their vitamin D levels (Cashman et al., 2020). 

It’s also important to ensure that you have a good amount of calcium in your diet as it works synergistically (together) with vitamin D. Dairy products are among the most well-known and rich sources of calcium. This includes milk, cheese, yogurt, and fortified dairy alternatives like almond or soy milk. Dairy products not only provide a high amount of calcium but also contain a little bit of vitamin D and are typically good sources of protein.


Final Thoughts

Vitamin D is important for general health and helping you get the most out of your training. The key is to maintain adequate levels, especially during Winter.

Across the Summer months, sensible sun exposure is recommended, while in Winter, supplementation is advised for most people. By understanding and managing your vitamin D levels, you can better protect your health, exercise recovery and overall performance.

Dr Daniel Owens, PhD SENr

Dan is our Lead on Strategic Development, Research and Innovation. He has worked as an academic for several years and published over 25 research articles in world-leading journals, alongside several book chapters. Dan’s primary role at The Edge HPL is to develop innovative nutritional strategies that fuel winning performances; whether that be on the playing field, in the boardroom or within the home / family environment.


Recommended Reading

Chen TC, Chimeh F, Lu Z, Mathieu J, Person KS, Zhang A, Kohn N, Martinello S, Berkowitz R, Holick MF. Factors that influence the cutaneous synthesis and dietary sources of vitamin D. Arch Biochem Biophys. 2007 Apr 15;460(2):213-7. doi: 10.1016/ Epub 2007 Jan 8. PMID: 17254541; PMCID: PMC2698590.

Cashman KD. Vitamin D Deficiency: Defining, Prevalence, Causes, and Strategies of Addressing. Calcif Tissue Int. 2020 Jan;106(1):14-29. doi: 10.1007/s00223-019-00559-4. Epub 2019 May 8. PMID: 31069443.

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