A Guide to Vitamin D - All You Need to Know

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Posted: 23/02/2017 Print

A Guide to Vitamin D - All You Need to Know

Guest blog by Sam Hadadi,

Lucy Bee Guide to Vitamin D

23rd February 2017 - an update to this article from Daisy Buckingham MSc ANutr,

In the beginning of February this year (2017), a study that was led by Queen Mary University of London, found in a systematic review and meta-analysis of previous research that by supplementing with vitamin D, it helped to protect individuals against acute respiratory infections. This includes the common cold and the flu!

The analysis of 25 randomised controlled trials (the gold standard for clinical trials), found that vitamin D supplementation reduced the risk of developing acute respiratory infections in all participants - this was seen in those taking daily or weekly supplementations.

This supplementation was found to be highly effective in areas and cases where vitamin D deficiency is common (Martineau et al., 2017). It is thought that vitamin D helps to boost levels of antimicrobial peptides, which are natural antibiotic substances.

During the winter months the frequency of cold and flu increases, which coincides with when our vitamin D levels are lowest (Queen Mary University of London, 2017).

During the autumn and winter months it is advised that adults and children over the age of 1, should be taking 10mcg of vitamin D a day. This is to maintain our vitamin D levels during the months where we cannot synthesise vitamin D from the sun (NHS, 2016).

This doesn’t mean that you need to go out and buy super strong vitamin D supplements, in fact that’s the opposite of what we want to do, since high doses of vitamin D supplements can have a negative impact on us and our bone health. It is more about making sure you’re getting vitamin D from your diet, and from 10mcg supplementations if you are at risk of vitamin D deficiency, or during the winter months.

Unless you’re lucky enough to be lying on a beach in the Caribbean, then chances are that when it comes to vitamin D, you need a top up.

As the current superstar on the block, heaps of recent studies have told us just how good vitamin D is for us. Yet despite this, far too many of us Brits are deficient in this “sunshine vitamin” - and we don’t even know it.


Given just how good it is for us, it’s not surprising that health bods have warned that a D-ficiency is perhaps the most dangerous vitamin deficiency of them all. From bone health to fighting depression and even protecting us from diseases including cancer, diabetes, stroke and heart disease, vitamin D is crucial for a happy and healthy body.

Wondering if you get enough and why you need it? You’re in the right place! If you want to learn all about this impressive vitamin, then read on for our ultimate Lucy Bee lowdown.

What Is Vitamin D?

Before we get into the nitty gritty, we’re going to teach you exactly what vitamin D, a fat-soluble vitamin, is and where it comes from. After all, the more knowledgeable we become, the better equipped we are to tackle a problem…

Much like plants need sunlight to grow and thrive, us humans do too. While we can get small amounts of vitamin D from food sources such as oily fish, this alone isn’t enough and we need lots of sun to keep our body nice and healthy.

When we’re exposed to sunlight or ultraviolet B light from artificial sources (think those bluish-hued SAD lamps), vitamin D3 is created in our skin. Once Vitamin D enters the body, it travels through the bloodstream to the liver before being converted into the pro-hormone calcidiol.

Ultimately, calcidiol then works its magic to transform into calationol, which circulates as a hormone and regulates all sorts of things, from mineral concentration in the blood to the functioning of the neuromuscular and immune systems.

Port Douglas

While it may sound pretty scientific and complicated, all you really need to know is this – our body needs vitamin D to survive and thrive as it can affect as many as 2,000 genes in the body.

While we can make small amounts of vitamin D in our body anyway, most of us need that extra boost from our diet, the sun, or from supplements in order to maintain adequate levels.

Why Do I Need Vitamin D?

Why do we love vitamin D? Well, let us count the ways…

This clever little vitamin is often underrated and it can do far more for our body and health than meets the eye. Here’s exactly what you can do for your body by avoiding a serious D-ficiency:

Boosts Calcium

Vitamin D works a treat at controlling calcium and phosphate levels in the blood and it also supports both bone growth and strength. It works by increasing our absorption of calcium from the small intestine and, as a result, may help us to reduce the risk of osteoporosis. 

Strengthens the Immune System

All of us have “T-cells” in our body which work to protect us against any nasty kinds of bacteria and disease. Vitamin D is crucial in the formation and function of these cells and it can even stimulate your immune system to produce cathelicidins that kill off nasty viruses.

Fights Disease

From Multiple Sclerosis1 to cancer and heart disease2, there are plenty of diseases which studies have shown can be improved with higher vitamin D levels. Amazingly, recent studies have shown that up to 75% of cancers3 can be prevented by us getting enough Vitamin D.

This may be because vitamin D is responsible for so many genetic pathways in the human body, meaning that deficiencies can trigger chronic disease. On the flipside, get enough and you could protect the parts of our cells called telomeres – wondrous things that dictate exactly how our cells age4.

Perhaps it’s for this reason that we recently discovered that sunbathers could live longer than those who stay out of the sun completely. Just remember to stay sunwise!

Ease Inflammation

Love exercise? Then keep your vitamin levels topped up! A lack of Vitamin D can be an athlete’s worst nightmare and can cause inflammation in the body and soreness across the body.

Help Depression

Our newsletter regulars will know that Vitamin D deficiencies can trigger SAD7, or seasonal affective disorder. However, a wonderful way to fight this is by ensuring we get enough of this stellar vitamin.


It’s thought that having access to little sunlight can mess up our body clock which, in turn, leads to feelings of depression. It can also interfere with our levels of Serotonin, a chemical in the brain that can cause mood changes. Want to know how else you can treat SAD? Read our article here.

Given all this, it’s probably not that surprising that low vitamin D levels have even been linked to premature death. Have we got you stretching for the supplements yet…?

Signs You're Deficient In Vitamin D

Now we know just how important the sunshine vitamin is to our body and our health, it’s a little scary when you pause and think just how many people are deficient in it. Worryingly, scientists believe that 40%-75% of people are lacking in some way, while others put this number at around 1 billion people worldwide.

Why? Well, as you now know, vitamin D isn’t readily available in foods. And, if like me as I write this, you’re gazing out the window at drizzly grey skies and longing for sizzling sun and beaches, you know all too well that sunshine isn’t always a reliable option.

Worried you may be suffering from a D-ficiency? Here are some common signs that you may not be getting enough:

  • You’re feeling low or depressed, or suffering from bad moods
  • You have weaker muscles or fatigue
  • You suffer from chronic pain
  • Your bones fracture easily
  • You have high blood pressure
  • Your physical performance has become worse

You should also bear in mind that if you have darker skin, then you need even more sun exposure to produce the right levels of vitamin D. Of course, many of these symptoms can also point to other problems, so if you’re concerned, always consult a doctor first.

Don't Forget........


It’s wise to remember that all of the following can affect just how much vitamin D you’re getting:

  • Pollution
  • Sunscreen (please don’t ditch the sunscreen, though! And always wear it during peak sunlight hours). Interestingly, one study found that even though sunscreen significantly reduced the production of vitamin D, normal usage does not lead to individuals getting insufficient levels of vitamin D10
  • Working long hours in offices or indoors

If you want to boost your intake, then we have plenty of information to help you along the way, including why deliciously creamy avocados8 are so good for D-ficiency levels, and, also some handy information about the world’s healthiest diets9. Eat up and enjoy!

If you’re pregnant or a nursing mother, remember that you’ll need even more vitamin D to nourish both yourself and your baby. 

Sam Hadadi Signature

1. Vitamin D and multiple sclerosis

2. Vitamin D and cardiovascular risk

3. Vitamin D and cancer

4. How our cells age

7. A beginner's guide to SAD

8. Our obsession with the avocado

9. Which is the world's healthiest diet?

10. Does using sunscreen affect vitamin D levels?

References from daisy's update Feb 2017:

Martineau, AR. Jolliffe, DA. Hooper, RL. Greenberg L. Aloia, JF. Bergman, P. et al., (2017). Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. British Medical Journal, (356). Available here.

Queen Mary University of London. (2017). Vitamin D protects against colds and flu, finds major global study. Queen Mary University of London. Available here.

NHS. (2016). The new guidelines on vitamin D – what you need to know. NHS Choices. Available here.

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Lucy Bee is concerned with Fair Trade, ethical and sustainable living, recycling and eating close to nature with additive free products for health.

The views and opinions expressed in videos and articles on the Lucy Bee website/s or social networking sites are those of the author/s and do not necessarily reflect those of Lucy Bee Limited.

Please note you should always refer your health queries to a qualified medical practitioner.

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Sam Hadadi is an ex-BBC journalist and now a freelance writer specialising in fitness and food.

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