Winter training: Vitamin D and ultra-running

One in five people in the UK has low vitamin D levels, according to the NHS. It’s essentially a national condition during the winter, when a lot of us aren’t getting enough of the vital vitamin from sunlight.

It’s something I’ve only become aware of through regular blood tests as part of measuring my training progress. As I wrote back in December, my last few blood tests with Forth Edge showed ‘OK’ vitamin D levels, but they suggested they could be higher to support training performance. At the time, I was taking 1000iU supplements, although I’ll admit I wasn’t very consistent at taking it daily.

Like a lot of ultra-runners (probably!), I try to optimise my life to get the most from training (and vice versa). I treat my training schedule, food and sleep with a degree of seriousness and intention in order to get results later down the line. Discipline pays off. So, after seeing the results from Forth Edge, I decided to take a closer look at vitamins. I did some research and switched to a sports-informed vitamin D supplement from Health Span, upping my daily dose to 4000iU.

A word of caution here. I’m not medically trained, and my vitamin D levels were within the ‘normal’ range before upping my supplement dose. While there’s a body of research to suggest vitamin D is important for runners in terms of supporting musculoskeletal health, there isn’t much to say that ‘higher’ levels of vitamin D – over 60nmol/L – will do a whole lot more for you. Having said that, levels over 60nmol/L aren’t necessarily harmful either – it takes a lot to reach the tipping point into hypercalcemia (which means diarrhea, nausea, and a load of other lovely symptoms). Doctors / medical pros, please feel free to weigh in on the comments.

I can’t speak for anyone else, but I can say that I felt a difference on the higher dose. After just three days, I felt more energetic and focused.

In terms of translating that into running performance, it’s been difficult to gauge. I was working long hours in December, and then promptly picked up an injury. I kept on running (lightly) through the injury, and actually started a run streak two days after picking up a groin strain. That then took until the end of January to work itself out. It may seem odd to have started a run streak while injured, but I wanted to keep moving every day, however slowly, rather than allowing the Christmas festivities to mean unwanted weight gain.

Now we’re well into February, and I’m running every day and feeling great. I’d highly recommend looking into your vitamin D. You can subscribe to a postal sports service like me – which also measures other things – or ask your GP.

Here’s how my vitamin D levels changed over time:

10th October 2018 – 57.8

16th January 2019 – 49.5

15th May – 49.9

25th October – 54.1 (sporadically taking 1000iU)

20th January 2020 – 84.4nmol/L (taking 4000iU a day)

One of the cool things about using Forth Edge is the notes you get from doctors reviewing your results. Dr Nicky Kealy responded to my January test with ‘[your] vitamin D [is] now in [the] athlete range to support health and performance. CK (creatine kinase) reflecting muscle micro damage [is] marginally raised, reflecting [your] high impact training load’.

Now, the CK increase comes as no surprise to me. It’s probably down to the run streaks. But I have to say I don’t feel overly fatigued at the moment – both in training, and generally. I’m now 60 days into the latest run streak, and two weeks fully recovered from that injury. I consciously dropped my pace during January to protect the groin injury, and to allow my body to adjust to the new rhythm and training load.

Long may that run streak continue. I’d love to know what you think about supplements and running – what works for you? Let me know in the comments below.

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