Why you need to have vitamin D this season

Experts are currently urging that we supplement our diet with vitamin D[1]. This is because most of us have stayed indoors much more lately, and therefore we are likely to have a lower vitamin D status than any previous winter.But why is vitamin D so important and why can’t we get enough of it from our diet?

What is vitamin D and what does it do?

Technically vitamin D isn’t a vitamin - it’s classified as a prohormone because it’s produced by the body (with the help of sunshine ), unlike other vitamins which come from our diet.

Vitamin D supports the normal function of the immune system plus the maintenance of normal bones and muscle function. Between early April to late September in the UK, the body creates vitamin D with the help of sunshine, but the sun is not high enough in the sky to do this in the winter months.

Why is vitamin D sometimes called the sunshine vitamin?

Vitamin D is known as the ‘sunshine vitamin’ because we can make vitamin D from exposing our skin to direct sunlight! Just under the surface of our skin is an abundance of a substance called 7-dehydrocholesterol, which is converted to vitamin D when our skin is exposed to ultraviolet (UV ) rays of a specific wavelength [280-315 nm] from the sunlight.

How do we get vitamin D?

The majority of our vitamin D comes from exposure to sunlight, but this is limited by the season. There are only a few foods that provide a good source of vitamin D, including oily fish, liver, meat and eggs, and so we also need to consider supplements and food products that have had vitamin D added into them – known as fortified foods. Fortified foods can give our intakes of vitamin D a boost, so look out for commonly fortified foods such as breakfast cereals, and milk alternatives.

Can I get vitamin D through a window?

The UV rays needed to make vitamin D can’t pass through the windowpane, so make sure you get outdoors and allow your skin to be exposed directly to sunlight for short(! ) periods during the Spring and Summer months to help your body make vitamin D.

How much sun do I need to get enough vitamin D?

You need far less sun than you might think; as little as nine minutes of sun exposure can be long enough to make enough vitamin D for the day, although this does vary for everyone and is influenced by factors including skin tone.[2]

Can I get vitamin D from the sun in the Autumn and Winter?

Even on a sunny Autumnal or Winter’s day, you can’t make vitamin D from the sun in the UK; this is because the UV rays need to be a specific wavelength [280-315 nm] for you to produce vitamin D and the sun isn’t high enough in the sky between late September to early April for these wavelengths to be available.

How do I know if the sun is bright enough to get vitamin D from it?

The length of your shadow can tell you if you can make vitamin D; if your shadow length is shorter than your height then the sun is high enough in the sky for you to be making vitamin D, but if your shadow is longer than your height then you will not be able to make vitamin D even if it is a lovely sunny day.

Should I supplement with vitamin D?

Yes. Supplements are important; through the autumn and winter months (from late September to early April ) everyone in the UK should consider taking a daily supplement containing 10 micrograms (400 IU ) of vitamin D.

Are there different forms of vitamin D?

In foods and dietary supplements vitamin D comes in two forms, vitamin D2 (ergocalciferol ) and vitamin D3 (cholecalciferol ). Vitamin D2 is produced in plants, whereas vitamin D3 is found in animal products and is also the form that we make ourselves.

Vitamin D3 is almost twice as effective at raising vitamin D levels within the body; this doesn’t mean vitamin D2 doesn’t work, and as it’s a plant source it certainly has its place within vegan diets (vitamin D3 is usually made from lanolin in sheep’s wool ), but vitamin D3 may be a more effective choice.


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