We all know that the UK is not famous for its sunny weather. Only this week, The Guardian featured an article highlighting that we do not get enough sun in the UK for healthy Vitamin D levels. So why is it important and what can we do about it? Clinical Nutritionist, Suzie Sawyer, looks at the many functions of Vitamin D in the body and what we can do to keep our levels topped up.
Hardly a day goes by without a news story being released about Vitamin D, and for good reason; it fulfils a number of very important health functions. It is known as ‘The Sunshine Vitamin’ because it’s primarily made on the skin in sunlight, but unfortunately many people living in the Northern Hemisphere can often suffer from a deficiency, particularly during the dark winter months, but more worryingly throughout the year in these less sunny countries. And this includes the UK.
Vitamin D actually functions as more of a hormone than a vitamin because of its action on the skin. Other than sunlight, it’s found in oily fish such as salmon and mackerel, eggs, butter, milk and sprouted seeds.
There are actually two forms of Vitamin D: Vitamin D2 is produced by plants but is not as effective at raising blood levels as Vitamin D3, which is synthesised by the sun or obtained from the animal sources listed above.
Vitamin D’s main ‘claim to fame’ is its ability to facilitate calcium absorption and regulation, thereby building and maintaining strong bones and teeth. It also plays a key role in the regulation of the body’s immune responses, helping to fight off infections all-year round.
Although it is made by sunlight, conversely it’s unstable to light and, therefore, is lost during any processing. So foods in their natural states are much more effective at raising blood levels of Vitamin D than processed equivalents.
Vitamin D is crucial for healthy bones. Recent research, presented at the American Society for Nutrition’s Experimental Biology conference, indicated that Vitamin D may also hold the key to long-lasting physical function. It seems that higher levels are needed for the preservation of muscle strength, good bone health and greater mobility as people age.
It may surprise you to hear that peak bone mass is generally achieved around 18 years of age, after which time there will be a very gradual decline. This decline can accelerate with age when there is insufficient Vitamin D in the body and, indeed insufficient calcium (found in dairy foods and green leafy vegetables). It’s no wonder then, that there’s so much emphasis on getting sufficient amounts of Vitamin D from the very early stages of life.
We know that being in the sunshine generally makes us feel happier, but this may also be attributable to having higher levels of Vitamin D.
A Finnish research study has shown that people with higher blood levels of Vitamin D have a lower risk of depression. This large study involving over 5000 individuals aged 30-79 were found to have a lower incidence of depression; this was particularly noticeable in those making better lifestyle choices, confirming that both aspects were important in improving people’s mood. Those with higher levels of Vitamin D also had better metabolic health in terms of blood pressure, glucose and cholesterol levels, suggesting that this group generally ate better, and included Vitamin D either within their diet or by taking supplementation.
There have been many research studies evaluating the importance of Vitamin D and the prevention of a number of heart-related conditions. The results have, generally, been very positive in support of higher levels of the vitamin being protective, although there is still a bit more clarity needed around the various mechanisms responsible.
For example, Vitamin D appears to be involved in blood sugar control and the prevention of metabolic syndrome; the correction of markers that cause inflammation; keeping arteries free-flowing, thereby reducing blood pressure. The impact of Vitamin D levels in the body suggest that it is indeed involved in many functions with regards to keeping the heart healthy.
It is now well accepted that vitamin D is an important immune system regulator. The active form of Vitamin D known as ‘D3’, plays a crucial role in a number of aspects of immune function, but specifically supports increasing the body’s T cells that help to fight unwanted bacteria and viruses.
These cells rely on Vitamin D to activate them and are actually ‘dormant’ when there is insufficient Vitamin D in the blood. The link between immunity and Vitamin D is so conclusive that the European Food Standards Agency (EFSA) have approved a nutritional claim linking the two; you’ll often see this now on foods and, specifically, food supplements. ‘Vitamin D contributes to the normal function of the immune system’
The UK Department of Health issued specific guidelines for those population groups requiring supplementation; children up to the age of five, pregnant and breast-feeding women, those 65 years or over and dark-skinned people who don’t produce as much Vitamin D on the skin.
However, a recent report from the Scientific Advisory Committee on Nutrition (SACN), an independent advisory body to the government, has formulated draft proposals that supplementation is advisable for the entire population in the UK.
SACN have apparently recognised that we can’t rely on sunshine in the UK to meet the Vitamin D requirements. The proposals are only currently in draft stage, but with more than one in five people having low levels of Vitamin D, and bearing in mind its importance in so many health conditions, it seems likely and, indeed, prudent, that these recommendations are adopted.
You only need to spend 15-20 minutes per day in the sun with the skin unprotected (i.e, without sun cream) to make sufficient Vitamin D, so enjoy the sunshine whilst you can and boost your body’s health at the same time.
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 T Jaaskelainen et al. Higher serum 25-hydroxyvitamin D concentrations are related to a reduced risk of depression. British Journal of Nutrition. Published online doi:10.1017/S0007114515000689
 S Judd et al. Vitamin D Deficiency and Risk for Cardiovascular Disease. Am J Med Sci 2009 Jul:338(1):40-44