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Are you getting enough Vitamin D? Why do you need it and how much are we talking?

Introduction – What is vitamin D? Where does it come from? Why is it important?

The body of literature regarding Vitamin D intake for athletes has progressed quite a bit over the last decade, with a good chunk of it demonstrating positive links to immune function, protein synthesis and regulation and function of skeletal tissue. Research has looked into athletes from a variety of disciplines e.g. endurance runners, jockeys, dancers and gymnasts.

Interestingly, findings have shown that vitamin D levels are similar in athletes to that of the general population. This is somewhat problematic as active individuals often require larger quantities of nutrients due to the increased stress placed upon the body during physical activity.

Some of you may know that we can get vitamin D naturally through exposure to sunlight ultraviolet B (UVB) radiation; this is considered a primary pathway for intake of endogenous vitamin D3. The vitamin D3 is stored in plasma membranes in the cells in our skin. You won’t be surprised to read that since this is a nutrition blog, we can also source it through food! Hurrah! This comes in the form of vitamin D2 and represents a small exogenous intake via our diet.

How much do we need?

The institute of medicine has suggested that tolerable limits of vitamin D intake via supplementation is ~4000IU. Quite often 1000-4000IU are recommended for active individuals and individuals who struggle to meet recommended daily allowances (RDAs). Could you go higher or is there a risk of consuming higher dosages? Research has found no cases of toxicity with daily intakes of 30,000 IU per day, for an extended period of time – but I am definitely not recommending you try. The early figures are recommended but will depend on a number of lifestyle factors with YOUR life not Sally who’s always posting pictures of her food on IG and boasting about her Strava segments! Also worth mentioning, some research has highlighted that 15min exposure to unprotected sun can get you ~10,000-20,000 IU, in a light-skinned individual. Still, I reiterate, the earlier figures are advised.

Where do I get it from?

Now we know the primary and secondary sources, you might be sat there wondering if you’re getting enough vitamin D, how to assess if you need more or if you’re already getting enough to support your health and performance?

Let’s broach the sunlight exposure first. Even individuals who find themselves outside for long periods of the day or live in hotter countries could still need to source extra ways to increase their vitamin D intake. It is important to not start assuming certain things before we have asked questions – questions, give us answers, and answers allow us to make better informed decisions. Regarding vitamin D, here are some important questions to consider:

Ø What are people’s occupations? – are they indoors sat in an office away from a window all day?
Ø What sport they play? – Do they train/compete in a sport that is played indoors?
Ø Do they follow a religion?
Ø How old are they?
Ø Are they pregnant or post-natal and lactating?
Ø What is their current dietary intake looking like?

Research has also found vitamin D deficiencies in individuals who follow a religion whilst also living in hot/warm climates. This has been shown to be a cause of covering up large quantities of their body and/or not consuming foods due to conflicts with their religious beliefs. Furthermore, literature has also informed us that athletes who train/compete in hot/warmer climates, will often train first thing in the morning or last thing in the evening when it is cooler. As a result, they end up missing prime time vitamin D intake. This will be explained more later in the blog.

Living in the UK, were at a natural disadvantage to all year round warm conditions, so when the summer comes around, we jump for joy, pull on our lycra and spend as much time as possible exercising outside whilst being in the saddle, right!? This is great but there are some additional factors that come in to play here. Fortunately for us (cyclists), getting outside on the bike is much more fun that being sat on the turbo – I think we can all agree on that. However, your timing is important and can influence your intake of vitamin D. The recommendation for sunlight exposure during the sunnier months is five to 15 minutes of unprotected sunlight exposure between the hours of 10 a.m. and 3 p.m.

Easy there tiger, let’s talk this out and think this through. Putting on your lycra midday and heading out for a few hours just isn’t feasible for some. If you can do it, great, and I encourage you to take advantage. Going out first thing or later in the day can reduce your intake of natural UVB exposure. That being said, you don’t necessarily have to be pulling on the lycra and getting on the bike and I know some of you will be thinking, ‘what’s the point of putting on the lycra for a 15min sun exposed ride?’. In reality, if you can get outside during working hours to expose your arms and legs for 15mins, do it! It’s also good for the soul and feel free to smile at people in the process! If you can get on the bike, do that too, but I’m assuming it won’t be just for 15mins so make sure you’re being safe and stick on some lotion 😉. Hang on – what if I can’t do either?

Well let’s talk food!


You should be considering the type of diet you are consuming and whether you are including foods that contain natural sources of vitamin D. Some of the popular foods that do contain high levels of vitamin D include: salmon, egg yolks, sun-grown mushrooms, milk and orange-juice. You can/should also consider fortified foods such as cereal, which can also be doubled up for extra iron and fibre intake.

‘I eat all those foods Jason, so I don’t need to worry about sourcing out extra vitamin D intake’. Umm… no. Most research has identified a little as 50% of vitamin D consumed in our diet is absorbed, so we lose quite a bit this way – remember, the primary method is sun exposure.

The story so far.

You could be the individual that tries to consume vitamin D rich foods, but doesn’t get enough to meet guidelines (come to that in a bit, sit tight); works inside all day in an office job and can only get outside early doors or later in the evening….doesn’t leave you with many options does it!?

Well, if this is the case, we could and should now consider supplementation. Quite often, athletes do. Now is a perfect time to highlight that supplement use should always be approached carefully and if you’re ever in doubt, don’t take the supplement. As a registered performance nutritionist and a UK Anti-doping advisor, I have duty of care to highlight the risks and benefits associated with supplement use. With all supplements, you should be looking for the informed sport logo (see image on the right). I have attached this so you can actively look for it in future. This will help you to identify a supplement that has been batch tested, which means it should have been tested for traces of illegal and banned substances. In future, I would recommend using some of the popular bigger companies e.g. SIS, NutritionX and Health Span – all have registered with informed sport and invested time and money to get this approval. Oh and FYI – I am not a rep for any of these supplement companies – remember, the more info you have, the better informed you are to make decisions for your health and performance 😉.

Wow, that was a lot of information Jason! Granted, as always, I would rather you be better informed, to make a better judgment call for your health and performance. If you are unsure of any of the information disseminated in this blog, especially regarding whether you are getting enough vitamin D – please make sure you consult with a registered dietitian/nutritionist (hopefully me 😉) before you proceed with an action plan. Everyone’s requirements will be different and depend on a variety of different factors, as I have repeated many times. Please do not assume what works for someone else will necessarily work for you.

If you enjoyed the read today, if you have any questions, or want to request a future blog topic – please leave a comment! Why not leave a comment anyway, I would love to hear from you :-). For all enquires, please head over to the ‘Contact Jason’ tab and leave me a message.

…if not, grab your lycra and lotion and I’ll see you on the tarmac!


P.S. To stay up to date on all future blog releases, head over to my homepage on my website and sign-up to my monthly blog.

P.P.S. The next blog release is a part 1 of a 3 part series around Weight loss & Performance – I have a feeling you’re going to enjoy those!

Carswell et al. (2018). Influence of Vitamin D Supplementation by Sunlight or Oral D3 on Exercise Performance

Mirian de la Puente Yagüe et al. (2020). Role of Vitamin D in Athletes and Their Performance: Current Concepts and New Trends

Ogan & Pritchett (2013). Vitamin D and the Athlete: Risks, Recommendations, and Benefits.

Jason Fligg

I graduated with a Masters in Sport & Exercise Nutrition in 2015. Soon after, I became a registered performance nutritionist (MSc, SENr Grad). Since founding Jason Fligg Sport & Exercise Performance in 2016, I have worked with a range of athletes, at an elite and amateur level, helping them to achieve major and incremental performance gains by educating them in how to improve their dietary intakes. As well as practising performance nutrition, I am also a qualified Personal Trainer, L3 Sports Massage Therapist and a qualified teacher; currently lecturing further and higher education in Sport and Exercise Science and Health Studies.

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