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We're known for having a lack of vitamin D in our bodies in the UK, primarily because, let's face it, we don't get much sun, especially at this time of year.
When you're heading to work before the sun comes up and getting home after dark, you can go a whole winter without so much of a glimpse of that big yellow ball in the sky.
And you may be feeling a little down in the dumps because of it. Research has linked a lack of natural sunlight to seasonal affective disorder, and it's vitamin D that's at the heart of it.
Known as the sunshine vitamin, it's what our bodies produce when we're exposed to the sun's rays.
Of course there are well known dangers of sizzling in the sun all day without protection, but likewise, staying indoors and having no exposure at all can lead to vitamin deficiencies.
Herbalist and nutritional therapist Andrew Johnson said having a vitamin D deficiency is common between January and March.
"Research has shown that people who get the most colds and infections at this time of year are the ones who are lowest in vitamin D, because of the lack of sun," he remarked.
What he's suggesting is that as well as affecting our moods, a lack of vitamin D can also have a negative impact on our immune systems.
If you're about to jet off on a holiday in the sun, then you should be able to boost your levels quite easily. Just remember to take all the necessary precautions to protect your skin.
If a getaway isn't on the agenda any time soon, then nutritional supplements could be your best bet.
Mr Johnson recommended having your vitamin D levels checked out, then you'll know which products to take and how much.