Vitamin D – Don’t assume anything!


You may think spending time in the sun in summer and supplementing in winter may be enough to give you optimum vitamin D levels. But this may not be the case.


Helen Marsden

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Why have a Vitamin D test? Can’t we just assume that if we spend enough time out of doors and possibly top-up with a supplement in winter that we will have optimum levels? Well no we can’t because unless you know your starting point it is difficult to know what level of supplementation you need, if any.

Take our medi-guinea pigs who last year all got their Vitamin D levels tested in the name of scientific investigation (no, these weren’t properly conducted trials but they are informative nonetheless!).

Our medi-guinea pigs include Medichecks directors Ceri, Helen (me) and Alistair, marketing guru, Hattie and my teenage daughter Hebe. Not a huge sample, but reasonably diverse in terms of age, skin colouring and sun habits.

Ceri and Hattie and I all had our Vitamin D levels checked last October so should in theory all have high levels from the recent summer. Ceri and I are brother and sister and we are both fair skinned, are both keen runners and therefore spend a good deal of time outside. I live in London and take a moderate/high strength Vitamin D supplement (2500 iu per day), Ceri lives in Scotland and assumed that his outdoor lifestyle would mean his Vitamin D level would be fine – indeed he was so confident he was reluctant to even take the test! Hattie didn’t supplement but could only be described as a keen sun worshipper. Indeed, she had spent the winter months in Australia and took every opportunity to top up her tan during the UK summer.  Our test results were revelatory: mine was the highest at 127 nmol/L (under 25 nmol/L is considered deficient, 25 – 50 nmol/L is considered insufficient but not deficient, 50 – 200 nmol/L is considered optimum while over 200nmol/L is considered potentially harmful), Hattie’s was the second highest at 106 nmol/L while Ceri’s, at 31 nmol/L was firmly in the deficient range. I think it is safe to assume that being outdoors in Australia is much more beneficial than being outdoors in Scotland – Ceri is clearly living in the wrong Perth for his Vitamin D level!

So what of the other medi-guinea pigs? My teenage daughter Hebe is typical of most students, becoming nocturnal as soon as her exams finished and even when awake during daylight hours spending most of her time in a darkened room on her computer.  I thought that a Vitamin D check might encourage her to spend more time in daylight, but the results of her blood test made me eat my words – her Vitamin D level at the end of January was 68 nmol/L – not the highest but considering the time of year, not bad. My daughter is extremely fair skinned and lives in London so perhaps that combination can get sufficient Vitamin D even in the depths of winter. No chance of me getting her to go outside now!

Like Ceri, fellow director Alistair has never supplemented with Vitamin D but like Hattie, he enjoys a good suntan so would take advantage of a nice day in Nottinghamshire to bask in the sunshine. His first blood test test in April showed a Vitamin D level of 68 nmol/L which was fine, albeit at the low end of the optimum range. However, later tests this winter showed a falling off of his Vitamin D level to under 50, falling to 41 nmol/L by mid February this year. I think it is safe to assume that his Vitamin D level would continue to fall unless he supplemented or got some sunshine.

But how much to supplement? On getting his result last October Ceri decided to supplement with a high street brand of Vitamin D. He took the recommended does of 400 iu per day. A re-test in January showed that his Vitamin D level had increased marginally from 31nmol/L to 35nmol/L. Ceri decided to double the dose he was taking to 800iu and a further test one month later actually showed that his Vitamin D level had declined again to 30 nmol/L – even lower than it was before he supplemented (but after 4 months of the Scottish winter). Clearly higher levels of Vitamin D supplementation are necessary to counteract the effects of living high in the Northern hemisphere. So don’t assume that just because it says Vitamin D on the bottle that it is doing enough to get you up to the optimum level.

So, what next? Ceri is embarking on a mission to see if he can increase his Vitamin D level through sunlight alone, I’m taking no chances and am going to keep taking my supplements. Alistair is going to enjoy the sun (if it ever arrives) and also take a moderate dose supplement to see the impact next October. Hattie is off to Thailand for some winter sun and Hebe is still holed up in her bedroom but at least can tell her mother to stop nagging!

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