Vitamin D levels through winter

Vitamin D levels through winter

At the end of a recent nutrition talk I did for a cycle club, someone asked me what was the most important of my recommendations for winter.  Optimising Vitamin D levels was my number one recommendation for a number of reasons.  Not least that levels in the general population (certainly in the UK and other northern countries) are now so low that they are becoming a major health concern.


Whilst sports people might be expected to spend more time in the sun, enabling the skin to synthesis vitamin D through ultraviolet (UVB) radiation exposure, research shows that most still have sub optimal levels.  For the athlete keen to optimise performance gains, ensuring optimal vitamin D status may have significant benefits beyond avoiding the low bone density and other problems associated with deficient levels.  For this reason, performance scientists working with elite athletes have focused much attention on vitamin D status, and there is now an increasing number of publications reflecting their findings.

A recent study on Dutch athletes showed that nearly 70% of 128 highly trained athletes had an insufficient (50-75 nmol/l) or a deficient (<50 nmol/l) 25(OH)D concentration at the start of their study. (Backx et al. 2016).  They demonstrated that those with insufficient or deficient levels could achieve a sufficient level by supplementing with 2200 IU per day for 3 months.

Owens et al (2015) seemed in favour of a more aggressive approach.

Whilst at present it is not possible to give an ideal serum concentration of 25[OH]D that athletes should strive to achieve, there are data to suggest that values >75 nmol.L−1 have the potential to improve immune health and skeletal muscle regeneration following muscle injury (Barker et al., 2013; He et al., 2013). To achieve serum concentrations >75 nmol.L−1, we have previously demonstrated that supplementation with oral Vitamin D3 at a dose of 5000−1 for 8 weeks can effectively achieve this (Close, Russell, et al., 2013).

For those wishing to follow their suggestions it is worth remembering that 5000 IU is actually above the EU suggested maximum daily tolerable dose (4000 IU), so it’s possibly unwise to consume this kind of dose without monitoring levels regularly, and ensuring you are also taking some vitamin K. Other performance related papers suggest that 3000 IU / day works for most people.

You may be able to find some high dose vitamin D at the local supermarket which may be good value but ensure that it is D3 form since it has been shown to be ~87% more effective than D2.

Factor in that many fish oil supplements contain vitamin D e.g. 400 IU per STEALTH Omega Shot (also 51ug of vitamin K2), but demand has been high so order whilst stocks last.  Regular consumption of a high quality fish oil supplement is also high on my list of beneficial supplements so I would probably take at least 1 omega shot per day and then make up the rest with a specific high quality vitamin D supplement.


Omega ShotSTEALTH - Omega Shot Lemon Zest Flavour - Box (30x17g)

Quality and precision becomes more important if you are going to take a high dose, I’ve not seen any published data, but did hear that 38/40 supplements tested by a major hospital recently did not contain what was declared on the label.

For this reason, we sourced a medical vitamin D supplement and did an additional WADA drug screen to ensure that it’s safe for tested athletes - on the website in ‘marginal gains section’.  It’s not cheap but easy to titrate the dose according to needs and it’s the one I use.


Vit D supplementKORA - Liquid Vitamin D3 Supplement

Finally, ensure that you do not confuse IU and ug. 100IU = 2.5ug (different manufacturers use different units to declare vitamin D content).

If you are interested in getting your Vitamin D levels fully checked, these guys seem to do a quick and efficient check from a fingertip blood spot



Backx, E., Tieland, M., Maase, K., Kies, A., Mensink, M., van Loon, L., & de Groot, L. (2016). The impact of 1-year vitamin D supplementation on vitamin D status in athletes: a dose–response study. European Journal Of Clinical Nutrition, 70(9), 1009-1014.

Bashir, M., Prietl, B., Tauschmann, M., Mautner, S., Kump, P., & Treiber, G. et al. (2015). Effects of high doses of vitamin D3 on mucosa-associated gut microbiome vary between regions of the human gastrointestinal tract. European Journal Of Nutrition, 55(4), 1479-1489.

Dahlquist, D., Dieter, B., & Koehle, M. (2015). Plausible ergogenic effects of vitamin D on athletic performance and recovery. J Int Soc Sports Nutr, 12(1).

Owens, D., Fraser, W., & Close, G. (2014). Vitamin D and the athlete: Emerging insights. European Journal Of Sport Science, 15(1), 73-84.