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Vitamin D

Vitamin D

The sunshine vitamin
It’s at this time of year that I question my clients about their levels of vitamin D. It’s called the ‘sunshine vitamin’ because our body makes what it needs from the sun. But these short winter days with overarching cloud cover and a weak, intermittent sun do not provide the conditions we need to obtain optimal levels of vitamin D.

Can we get it from our diet?
You might think we could then compensate with our diet to obtain the levels that we need, but vitamin D is only found in foods of animal origin (so that already excludes all vegetarians and vegans being able to fulfill their needs). The most significant food source is oily fish and fish liver oil, although small amounts are also found in egg yolk, dairy fat, liver and other offal. These days some foods are fortified with added vitamin D including breakfast cereals, some processed milks and infant foods.

But what’s all the fuss about?
Vitamin D is possibly best known for it’s very important role in bone health [1]. It is essential for the absorption of dietary calcium, and helps to regulate blood levels of calcium and phosphorous, and the stimulation of bone mineralisation.
Other body functions that are related to body’s supply of calcium and phosphorous include maintaining a stable nervous system, normal heart action and normal blood clotting; vitamin D is essential in those functions too.

Vitamin D also has recognised effects on the regulation of cell differentiation, immunity and autoimmunity [2]. It is a crucial vitamin for a healthy immune system and insufficiency has been implicated in many different diseases including, cognitive and mood disorders, autoimmune disorders, infectious immune disorders and cardiovascular disease.

It has also been reported that vitamin D deficiency may predispose to glucose intolerance, altered insulin secretion and type 2 diabetes mellitus (T2DM). The replenishment of vitamin D improves glycemia and insulin secretion in patients with T2DM [3].

For my sports nutrition clients and athletes I wanted to highlight some interesting research in the sports arena. It has been shown that vitamin D may enhance protein synthesis, improve muscle strength [4] and postural and dynamic balance [5]. Vitamin D deficiency is associated with diffuse muscle pain, muscle weakness and a reduction in performance speed.

Do you have optimal levels?
The answer is probably not, because the majority of the UK population don’t have sufficient levels for optimal health [6]. I didn’t. It was a fairly sunny summer last year and I spent much time outdoors training for a marathon. However by Christmas I wanted to confirm my levels. My test results came back as 43.7nmol/L, which is described as ‘insufficient.’

Vitamin D levels are assessed by measuring 25-hydroxyvitamin D (25 (OH) D3) in the blood. The reference range on the test I chose used 50nmol/L as being what is termed ‘adequate’, but please bear in mind that adequate describes absence of disease and not optimal health. I aim for my own levels and that of my clients, to be at least 75nmol/L and preferably between 100nmol/L to 150nmol/L, which some experts believe are the levels necessary to reduce the risk of chronic disease [7].

After spending 2 weeks in the South African sun over Christmas I came back and re-tested my levels. They had improved to 78.7nmol/L but are still not high enough to ensure my optimal health, so now I happily drink my sunshine vitamin from supplemental drops.

Please bear in mind that vitamin D deficiency may be the most common medical condition in the world, and vitamin D supplementation may be the most cost-effective strategy to improve health, reduce disease and increase longevity [8].

What are your levels?
If you would like any advice about testing or supplementation options, then don’t hesitate to contact me and we discuss your requirements.

References
1. Bikle, D.D. 2012. Vitamin D and bone. Current Osteoporosis Reports. 10(2): 151-159
2. Antico A, Tampoia M, et al., 2012. Can supplementation with vitamin D reduce the risk or modify the course of autoimmune disease? A systematic review of the literature. Autoimmune Review. 12(2):127-36.
3. Palomer, X., González-Clemente, J. M., Blanco-Vaca, F. and Mauricio, D. 2008. Role of vitamin D in the pathogenesis of type 2 diabetes mellitus. Diabetes, Obesity and Metabolism, 10:185–197.
4. Heaney, R. P. 2003. Vitamin D Depletion and Effective Calcium Absorption. J Bone Miner Res, 18:1342.
5. Bischoff-Ferrari, H.A., Conzelmann, M., Stahelin, H.B. et al., 2006. Is fall prevention by vitamin D mediated by a change in postural or dynamic balance? Osteporosis International. 17(5):656-663.
6. Gillie O. 2011. Sunlight Robbery: the failure of UK policy on vitamin D: In search of evidence-based public health policy. Presented at the Vitamin D Experts’ Forum, London, April 2011.
7. Holick, M.F. and Chen, T.C 2008. Vitamin D Deficiency: a worldwide problem with health consequences. Am J Clin Nutr. 87(4):1080S-1086S
8. Murray, M.T. and Pizzorno, J. 2012. The Encyclopedia of Natural Medicine Third Edition. New York: Atria Paperback