Let the sun shine….with vitamin D….
20th February 2012
If anyone were to ask me after 4 or so years of studying nutrition what my favourite vitamin is the answer would be easy – vitamin D. Now I know having a favourite vitamin (and in fact vitamin D isn’t actually a vitamin, but more on that later) is a bit geeky but let’s face it, that’s what I am!
90% of our vitamin D is produced by the sun’s action on the skin. There is a nifty chemical process that occurs in the skin, liver and kidneys that makes most of the vitamin D we need. You need about 15 minutes in the sun, 3-4 times per week throughout the summer; without sun protection and with your arms, legs and face exposed. And the sun has to be shining – not hidden behind that big grey cloud that will undoubtedly release its cargo as you make a mad dash for the nearest doorway. And to top it off in the UK the sun isn’t strong enough to make vitamin D between October and March. Mother Nature is not very kind to us in the UK when it comes to vitamin D production! There are also a few sources of vitamin D in our diets, primarily from oily fish, liver and eggs and fortified foods such as margarine; but the levels are pretty low. We need SUNSHINE!!
So why is this vitamin so special? Well it’s all about what it does in the body. The list is endless and still growing. We’ve known for a long time that vitamin D is essential for the uptake of calcium in the body and this is why you often find supplements containing vitamin D and calcium together. Because of this synergy with calcium, low levels of vitamin D can lead to rickets (soft bones) in children, osteomalacia (soft bones) in adults and osteoporosis (thin and weak bones) in later life. We’ve know about this action for a long time.
More recently and arguably more exciting, researchers have found that vitamin D has a direct effect on the action of genes across our entire body. Genes control everything that happens. And this is why I say vitamin D is actually not a vitamin but a sort of hormone. This discovery has linked low levels of vitamin D to health issues such as cardiovascular disease, diabetes, cancer, infections, degenerative diseases, autoimmune conditions such as multiples sclerosis (MS) and obesity. This isn’t to say low vitamin D status is the cause of these conditions but it may well be a contributing factor. Are you starting to see why the sunshine vitamin is my favourite?
So how much vitamin D do we need to prevent deficiency? Well this is where we find the controversy. The current recommended nutrient intake (RNI) for vitamin D in the UK is set at 7mcg for the under 5’s, 10mcg for pregnant and breast feeding women, anyone who is over 65 years old and those who remain indoors or extensively covered when outside. Notice there is a no RNI for the general population. This is because the UK government think we will get all the vitamin D we need from the sun. Yeah right! The U.S and Canadian Governments think we need at least 20mcg of vitamin D as adults. All of this would be fine if the current research didn’t suggest wide-spread vitamin D deficiency in Europe (WHO 2010) with a deficiency rate of up to 70% (Pérez-López et al 2012).
The solution is pretty simple – supplementation. However, there is another obstacle in the way. Because vitamin D is fat soluble there are fears that it may accumulate in the body (stored in fat and the liver) and cause problems with toxicity. But this opinion is based on outdated science and in fact research has shown no toxicity at levels of 250mcg per day for up to 5 months in adult men.
I recently had my vitamin D status tested using a new finger prick blood test supplied by Pathology Department at City Hospital in Birmingham and was not surprised to find my levels were ‘insufficient’ at 48.3 nmol/L. This is because I’d chosen not to supplement vitamin D this winter in anticipation of this test. Now as a nutritionist I eat a very healthy, balanced diet and I try to get outside for exercise wherever possible. But I am stuck inside behind a computer for much of the day, like so many people. Our lifestyles have changed dramatically in the last 20 years since the advent of the internet and social networking but our bodies haven’t caught up with this indoor lifestyle. The research shows that vitamin D has wide ranging influence on the body so isn’t it about time we started looking seriously at raising the RNI and encouraging safe and effective supplementation?
Pérez-López FR Brincat M Tamer Erel C Tremollieres F Gambacciani M Lambrinoudaki I Moen MH Schenck-Gustafsson K Vujovic S Rozenberg S Rees M (2012) Vitamin D and postmenopausal health Maturitas 71 (2012) 83– 88