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The Sunshine Vitamin!

Autumn has arrived! And for athletes training in Wales and across the UK this means less sun exposure and more time spent training indoors leading to risk of vitamin D deficiency. 

So, what is vitamin D and why do we hear so much about this sunshine vitamin? 

Although we call it a vitamin, vitamin D is actually a hormone which is mainly produced in our bodies from direct sunlight exposure on our skin. There are a few foods which contain small amounts of vitamin D including oily fish such as salmon or mackerel, red meat, eggs and some fortified breakfast cereals and fat spreads. Although even a healthy, balanced diet which provides us with all the other nutrients that we need is unlikely to provide enough vitamin D. 

People living in the UK are at risk of low vitamin D levels particularly in the Autumn and Winter months when the suns UV rays are not strong enough to create vitamin D. Vitamin D is essential for our bones and this is because we need vitamin D to help our bodies absorb calcium and phosphate, which are important for healthy bones, teeth and even muscles. Vitamin D deficiency can cause bones to become soft and weak making them more susceptible to injuries. 

Vitamin D also plays an important role in many aspects that may impact on an athlete’s overall health and ability to train including their muscle function and immune health. 

Some athletes may be at greater risk of low vitamin D levels, particularly those that spend very little time outdoors in the summer or for those whose training is predominantly based indoors. Similarly, athletes who cover up most of their skin when outside, for example with specific training kit or who routinely use sunscreen may also be more likely to have low vitamin D levels. Athletes with darker skin tones from Asian, African, Afro-Carribean and Middle Eastern descent living in the UK may also be more at risk of low vitamin D levels.


In the UK all adults and children over the age of one are advised to consider taking a daily supplement containing 10 micrograms (400IU) of vitamin D especially during the Autumn and winter months. Athletes are generally recommended to consider taking a slightly higher amount of 25-50 micrograms of vitamin D (1,000-2,000IU) per day between October and April. 

Too much vitamin D can also be harmful to the body and therefore athletes are advised to check all the supplements that they take to ensure they don’t take more than the upper limit. Children aged 1-10 shouldn’t take more than 50 micrograms (2,000IU) daily and adults shouldn’t exceed 100 micrograms (4,000IU) daily.

Athletes must be very cautious when it comes to using supplements due to the genuine risk of contamination with prohibited substances. Consequently, all athletes are required to assess the need, risk and consequences before taking any supplementation in accordance with UKAD guidance on managing supplement risks. In addition, athletes are required to retain a record of all supplements taken. 

To support athlete’s during this time, the Sport Wales Institute Performance Nutrition and Clinical teams have developed the athlete vitamin D guidance. While some athletes are at greater risk of vitamin D deficiency than others, it is recommended that all athletes consider taking a vitamin D supplement to support their health and performance during the autumn and winter months (from the beginning of October until the end of March). 

Some useful resources with further information include:


Olivia Busby, MSc, SENr

Lead Performance Nutritionist 


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