Vitamin D – here’s what you should know

As the clocks go back in England this weekend and we enjoy some beautiful autumnal days, shorter days means less sunlight and consequently less vitamin D for our bodies.   But is this really a big deal?

Over the last few years interest in vitamin D has increased, and for good reason.   Vitamin D has many functions – it regulates the amount of calcium and phosphate in the body, vital for healthy bones, teeth and muscles. It also plays an important role in supporting immunity, especially important in these winter months, and in reducing inflammation in the body. Low vitamin D is also thought to be a risk factor for many health conditions including cancer, heart disease, depression and autoimmune conditions.

Latest research shows that over 20% of adults and children in the UK have low levels of vitamin D in their blood. Vitamin D has a half life in the body of no more than 6 weeks, meaning that 6 weeks after your summer holiday your body’s stores of vitamin D have been depleted. And given that it is impossible to get your daily requirements from food, it makes sense that this is one vitamin it is good to supplement throughout the long, grey winter.

But vitamin D deficiency isn’t just a problem in the winter months. Advice to cover up and apply high factor sunscreen in the summer means exposure even when it’s sunny can also be limited. And other lifestyle factors such as extended periods of time spent indoors (long hours working in offices or inside watching TV or playing computer games), as well as a decline in the ability to produce vitamin D as we age all add up to a population largely producing insufficient levels of vitamin D.

Government guidelines[1] have recently been updated to recommend that everyone needs a daily intake of vitamin D equivalent to 10 mcg (around 400iu), particularly important between the months of October and March when the sun simply doesn’t contain enough UVB for our skin to produce vitamin D. At risk groups have long been recommended to supplement, but this recent advice applies to the entire UK population.

How much do I need to take?

While current guidelines recommend taking 10mcg (400iu) daily, individual requirements may vary. These recommendations are the minimum requirements for the majority of the population, sufficient to keep diseases such as rickets at bay. As such, these levels are unlikely to be sufficient for most people looking to achieve optimal health. Vitamin D is a fat-soluble vitamin, which means it is stored in our body’s fat supplies (unlike other water-soluble vitamins where excesses are excreted in urine), so taking too much vitamin D can be toxic. Additionally, too much vitamin D is linked with increased cardiovascular disease, kidney stones and a reduction in bone density. It is therefore recommended to have a vitamin D blood test which will determine your current levels of vitamin D, and supplementation can be taken accordingly. Vitamin D comes in 2 forms: D2 (ergocalciferol) and D3 (cholecalciferol). While both forms raise 25(OH)D levels in the blood (25(OH)D levels are tested in the blood to determine how much vitamin D we have in our bodies), D3is recommended because it is the more active form.

Dietary sources

While diet alone won’t provide your daily requirements, every little helps, and it is possible to get some vitamin D in the diet. Dietary sources include fortified foods, oily fish, organic whole milk (semi skimmed, due to its reduced fat content, contains less vitamin D because it is a fat-soluble vitamin), red meat, liver, mushrooms, and egg yolks. And as its a fat-soluble vitamin, making sure your meals contain some fat will help absorption.  

And if all else fails, there’s always that winter holiday in the sun …..

[1] Public Health UK

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