The Sunshine Vitamin

What is Vitamin D?

Known as the sunshine vitamin, Vitamin D is crucial for bone health, muscle function and repair and immunity. It’s actually a hormone which regulates many different processes and we make it in our body is exposed to UVB rays in sunlight.

We can also consume it in foods such as oily fish, eggs and fortified foods, but we only get 10-20% of the amount we need from food. We get 80-90% our Vitamin D from exposing our skin to sunlight.

Although sun exposure is the primary source of vitamin D for most people in the UK, during the winter months (roughly September to April), when the sun's rays are not as strong, it becomes more challenging to get enough vitamin D from sunlight alone.

Food Sources

• Oily fish such as herring, salmon and mackerel

• Mushrooms

• Egg yolk

• Meat (particularly organ meat like liver)

• Dairy

• Fortified cereals and m*lks

Role in Health and Performance

Vitamin D is an essential component that our body uses in a tightly controlled mechanism to regulate the calcium availability and absorption in our body, without it your body can’t absorb and use calcium properly. In this way it contributes to bone health, helping children and teenagers develop strong, healthy bones and older populations to maintain their bone density and avoid fractures and brittle bone diseases like osteoporosis in later life. 

It also plays an important role in regulating our innate and acquired immunity, contributing to the normal functioning of the immune system and our response to illness and infection.

Importance for athletes

Minimising Illness and Maintain Availability

Vitamin D deficiency has been shown to increase incidence of Upper Respiratory Tract Infection and increase the number of days with symptoms. So if your Vitamin D levels aren’t high enough you are more likely to get ill and have more symptoms which can reduce your availability to train or compete. 

Improving Recovery

Supplementing with Vitamin D can improve the repair and remodelling of muscle. Studies have shown a reduction in post-exercise muscle damage and improved recovery when athletes with low vitamin D status took a Vitamin D supplement for 6 weeks.

Reducing Injury risk

With the potential for bone health to be compromised if you have insufficient Vitamin D, Athletes can increase their risk of stress fractures if they don’t stay on top of their Vitamin D intake.

Athletes with a higher risk of deficiency

If you have dark skin, or usually wear clothes that cover up most of your skin when outdoors, or you typically wear sunscreen, you may be at increased risk of deficiency. If you play a weight-bearing sport you should have good bone mineral density as load-bearing exercise is osteogenic, which means it helps build bone density. But if you participate in a sport where your body weight is supported, such as swimming, cycling or rowing you won’t necessarily have the benefit of that stimulus and may benefit from an increased Vitamin D intake.

Choosing the right supplement

The recommended dose in the UK for all adults and children over the age of one is 10μg/400IU daily year round and especially during Autumn and Winter. Athletes may benefit from higher doses and there is growing evidence that higher doses are required to prevent or correct deficiency.

The European Food Safety Authority (EFSA) and Institute of Medicine (IOM) have set a Safe Upper Limit of 100μg/4,000IU daily. This upper limit exists as Vitamin D is stored by the body and not excreted so there is the potential for a toxic dose. Also, much higher doses (more than 10,000IU daily) have been found to have detrimental effects on bone health.

An intake of 1,000-2,000 IU daily is an appropriate intake when you don’t know your Vitamin D status. Vitamin D3 is more effectively absorbed than D2. Other things to consider are what will help you be most consistent with taking your supplement for 6 months? Some prefer a tablet, other athletes like to use a spray, particularly if they have other tablets to take.

So, while athletes may benefit from higher doses than the rest of us, this should be tailored to the individual as taking too much can have negative effects. I recommend you have a blood test to find out your vitamin D status and get advice from a registered nutritionist.

And as with any supplement, it’s important that you reduce the risk of inadvertent doping by choosing a supplement which is 3rd party batch tested by someone like Informed Sport.