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What is Vitamin D and why is it so important?

29 Sep 2021 • 7 min read


Vitamin D can help maintain your immune system and support strong bones, but did you know it is actually a hormone rather than a vitamin? Confused? Don’t be. Here is all you need to know about the ‘Sunshine Vitamin’.

As we are spending more time in our homes, a daily dose of Vitamin D has never been more important to help you and your family stay well.

When your body gets Vitamin D (from sunlight, food, or supplements), it turns the Vitamin D into a hormone. This hormone is called activated Vitamin D, or calcitriol, which is very important to your overall health and wellbeing.

Your body makes around 90% of the Vitamin D it needs, but this can only happen when your skin gets enough direct UV light from sunshine.

The other 10% of your Vitamin D intake comes from foods rich in the vitamin. If you do not get a lot of sunlight, or if you usually stay covered up, a quality Vitamin D supplement will help you.

What does Vitamin D actually do in my body?

Vitamin D is important for a huge number of functions in the body, from supporting strong and healthy bones to maintaining your immune system.

Most of your body’s Vitamin D comes from getting enough sunlight on your skin. For many people, this is a challenge, which is why new Government guidelines recommend a daily Vitamin D3 supplement.

It has also been shown to support the immune system. So taking Vitamin D during the winter months, when you may be more likely to feel under the weather, could help support your immune system, which is integral in fighting off bugs.

5 surprising facts about Vitamin D

1. It helps build strong bones

Our bodies need vitamin D to extract calcium properly from the food we eat, but a vitamin D deficiency means we cannot absorb enough calcium.

Over time, this can contribute to osteomalacia – a condition where the bones become weak and more likely to fracture. But upping your vitamin D levels helps remineralise bone structures, making them stronger.

It could also help prevent osteoporosis. While osteomalacia is caused by poor bone structures being built, osteoporosis is caused by bone breaking down.

Some studies have found that the vitamin can also slow down bone loss, warding off osteoporosis and keeping you stronger for longer.

2. It can protect against gum disease

Finnish researchers recently discovered that low vitamin D levels are linked to periodontitis, or gum disease. Their study found those with chronic gum disease also had very low levels of vitamin D in the blood.

A further study in Norway has also found a link between tooth loss and exposure to sunlight – only 11 per cent of those living in the south of the country lost teeth, compared with 65 per cent in the north. If only we could get summer holidays on prescription…

3. It can help keep your muscles strong

Muscle weakness may be another side effect of low vitamin D levels, especially in the elderly.

Numerous studies have found that taking supplements of this vitamin significantly improves muscle performance, in turn decreasing the number of injuries suffered from falls.

In one particular trial, residents in a nursing home who received this healthy vitamin and calcium supplements suffered 72 per cent fewer falls than those taking a placebo.

4. It may help improve heart health

A recent study – and the largest ever done on the subject – concluded that a vitamin D deficiency is linked to heart disease.

Over 70 per cent of nearly 1500 patients undergoing investigation for narrowing arteries had a vitamin D deficiency, and there was a 32 per cent higher occurrence of coronary artery disease in those patients with the lowest vitamin D levels.

The results were so clear, the team now want to investigate the effects of taking vitamin D on boosting heart health.

5. It can support brain function

This vital vit could have benefits for both mind and body; evidence shows there are links between low vitamin D levels and dementia.

It can be found in brain tissue and two large studies recently suggested that low vitamin D levels could increase the risk of developing dementia. Researchers now agree that large-scale studies should be carried out to fully investigate the link.


Did you know? Vitamin D:

  • helps build strong bones
  • can protect against gum disease
  • helps keep your muscles strong
  • may improve heart health
  • can boost brain function

How does sunlight give us Vitamin D?

When we get sunlight on our skin, our body produces a substance called cholecalciferol.

This is then turned into calcidiol and then calcitriol by the liver and kidneys.

Calcitriol (the active form of Vitamin D) is what your Doctor would measure to assess your Vitamin D levels.

There are three ways to get enough Vitamin D:

  1. from exposure to enough sunlight on your skin
  2. from food sources
  3. from a good Vitamin D supplement

During sunny months, your body might make excess calcidiol. But it will not go to waste. Any extra will be stored in your body fat as a kind of back up for those grey winter days.

Experts think that just 10 minutes of sunlight on your skin is enough to avoid Vitamin D deficiency. So get outside when you can!

What are the symptoms of a vitamin D deficiency?

A vitamin D deficiency can lead to rickets in children and osteomalacia or osteoporosis in adults.1 It causes the bones to become soft and weak, often leading to deformities and a higher risk of fractures. Other symptoms include:2

  • growth problems
  • bone and joint aches
  • greater risk of infections
  • gum disease
  • constipation

How much vitamin D do I need?

We need 10mcg of vitamin D a day.3 Between April and September, around 15-20 minutes of direct sunlight can provide you with enough vitamin D, but this will vary according to your skin type.4 In autumn and winter the sun isn’t strong enough in the UK for us to produce vitamin D, so it is recommended that everyone from the age of one takes a daily supplement of 10mcg.5  For vulnerable groups who do not get enough sunshine – people with darker skin, those aged 65 or older, people who cover up for religious or cultural reasons, for example – a year-round vitamin D supplement is advised.6

How much vitamin D do children need?

Babies under the age of one need 8.5mcg to 10mcg a day. Older children need the same amount of vitamin D a day as adults.7

Vitamin D2 and D3

The most important forms of Vitamin D for the human body are D3 and (to a lesser extent) D2.

Make sure you cover your bases by choosing a quality vitamin supplement and eating some foods fortified with D3.

What is the difference between vitamin D2 and D3?

Vitamin D2 and D3 are the two most important forms for your health.

There are 2 main forms of vitamin D:

  • Vitamin D2 (ergocalciferol) made by plants, with wild mushrooms and those grown under a UV light being the best source
  • Vitamin D3 (cholecalciferol) made by our skin when we are exposed to enough sunlight. Animal products like fish, meat, eggs and dairy as well as a vegan-friendly fungus called lichen also naturally contain this type of vitamin D

Fortified foods can contain either form.

Is vitamin D3 better than vitamin D2?

Studies show that Vitamin D3 is far more important for our health than Vitamin D2. So either choose a Vitamin D3 supplement, or one which contains optimal levels of both forms. Vitamin D2 on its own is not enough.

Experts used to think that vitamins D2 and D3 were of equal importance for human health. But this was based on outdated studies of rickets in children. These days, we know lots more about Vitamin D. And it is clear that D3 is far more important – and more effective – for our health and wellbeing.

We need to look at how the body absorbs Vitamin D to understand why Vitamin D3 is more important. There are lots of biological processes involved. A specific enzyme in the liver helps Vitamin D3 metabolise into the bioactive form of Vitamin D. This process takes much longer with Vitamin D2.

All about Vitamin D2

Plants produce this form of Vitamin D when they are exposed to UV light (in much the same way as our bodies naturally produce Vitamin D).

The most common example is wild mushrooms or mushrooms produced under UV light. Dairy-free milk (including soya, coconut, and almond milk) are often boosted with D2.

All about Vitamin D3

Vitamin D3 is the biologically active form of the vitamin, found in our bodies and in animals. When sunlight hits exposed skin, a reactive process converts cholesterol into Vitamin D3.

Although you need both forms, Vitamin D3 is more important for your health and wellbeing. Our bodies absorb and use Vitamin D3 better, and it is more effective at treating diseases.

Studies have shown that it is Vitamin D3, not D2, which maintains levels of Vitamin D in our body even over winter months.

It is important to note that dietary sources of Vitamin D3 can only be found in animal products. So if you are vegan, you need to pay extra attention to supplementing your diet with Vitamin D3.


  • Vitamin D comes in two forms: D2 and D3
  • Studies show that Vitamin D3 is more important for our health and well being
  • Dietary sources of D3 can only be found in animal products
  • Vegans are therefore advised to supplement their diet with D3

What happens when you take your daily Vitamin D3?

When you take a Vitamin D supplement, the vitamin passes from your bloodstream into your liver.

From here, it goes to the kidneys where it turns into calcitriol.

It is then released back into your bloodstream and can now enter your body’s cells where it attaches to Vitamin D receptors.

At this point, it can get to work regulating the minerals calcium and phosphorous. Clever stuff!

In your bones

Vitamin D in your bones helps absorb and store calcium in your skeletal tissue. It regulates the cells which build and maintain bones.

In your kidneys

Vitamin D helps recycle calcium in your kidneys so your bones can reabsorb it. If this did not happen, you would lose more of your Vitamin D through urination.

In your digestive system

Vitamin D also gets to work in your intestines. Here, it helps your body absorb the calcium from your healthy diet and from any calcium supplements.

Make sure you get enough Vitamin D in a format which your body can use. Support your diet and lifestyle with a quality daily Vitamin D3 supplement which can be absorbed and digested by your body.

Which foods are the best sources of vitamin D?

Foods that contain vitamin D are:8,9

  • oily fish, such as sardines and salmon
  • fish and algae oil supplements
  • eggs
  • red meat, especially liver
  • milk
  • fortified plant milks
  • fortified cereals
  • mushrooms

What are the benefits of taking a vitamin D supplement?

The government says around 25% of teenagers and adults in the UK have low levels of vitamin D, which puts them at risk.

As there are so few food sources of vitamin D, and sun exposure can be unreliable, supplements are considered a safe way to prevent a deficiency.10 

A 2013 review of evidence concluded that a vitamin D supplement could help protect against coughs and colds, while a separate 2013 study reported that women with lower levels of vitamin D experience tiredness and low energy.11,12

With so many factors putting us at risk of low levels, it makes sense to look at ways to supplement.

Some foods are fortified with Vitamin D, although you need to be sure it is Vitamin D3 and not just Vitamin D2.

Cod liver oil is a good source of Vitamin D supplementation (but not a suitable choice for vegans).

A quality Vitamin D3 or wide-spectrum Vitamin D supplement is a sensible way to keep your daily levels topped up.

The most helpful aspect of taking any trustworthy health supplement is peace of mind. Just one little tablet or capsule per day and you can carry on knowing that you have covered your health bases.

With Vitamin D, you will be protecting your bone health, supporting your immune system, and helping your body build and maintain cells. That is why Vitamin D is one of the most important supplements you can take.

How to get more Vitamin D in your day

Vitamin D is important for a host of health functions, from strong bones to a robust immune system.

These strategies will help you get more Vitamin D into your day:

Before breakfast

If the sun is up before you go to work, get outside.

Sit in a sunny corner of your garden with your first cuppa of the day, or take the dog for a short stroll. The sunshine on your skin will boost your Vitamin D production.

Breakfast choices

Make smart choices at breakfast to increase your Vitamin D. Whole eggs and oily fish are great sources.

Scrambled egg with wild smoked salmon is perfect. Or choose a breakfast cereal or instant oats brand fortified with Vitamin D3.

Orange juice and non-dairy milk drinks like soya and almond milk contain Vitamin D.

Daytime sunshine

If you can, get outside during the sunniest part of the day, it will be great for your Vitamin D levels.

Roll up your sleeves to expose your hands and forearms, and go for a short stroll in the full sunshine.


Tinned tuna is a good source of dietary Vitamin D and is a convenient choice for lunch on-the-go. Try it as a topping for a jacket potato, or as part of a healthy salad.

An evening stroll

Have you got time for a short walk before dinner? Wind down after your busy day by going for a walk with your kids or partner and get away from the TV and into the sunlight.

What’s for dinner?

Add some Vitamin D sources to your evening meal. Choosing oily fish like wild salmon and wild-grown mushrooms.

Your daily dose

Finally, take a daily Vitamin D supplement to cover your everyday dose of Vitamins D2 and D3. It is a cost-effective way to get peace of mind all year round.


Tips to increase your levels of vitamin D include:

  • Getting out in the sunshine
  • Safely exposing your hands and forearms to full sunshine
  • Eating food stuffs naturally rich in Vitamin D as well as fortified foods
  • Eating more oily fish
  • Taking a supplement that contains D2 and D3

Which type of vitamin D is best for you?

If you would like a little more of the sunshine vitamin in your life, but do not know which type of vitamin D is best for you, don’t worry - we’re on the case!

Our nutritionists have created a handy guide outlining which type and form of vitamin D will help you thrive.

Whether you are looking for vitamin D for adults, vegans, children and babies or for when you are pregnant, there is a suitable type for everyone.

Do I need to take a vitamin D supplement when I’m pregnant?

It is especially important to make sure your vitamin D levels are topped up when you are pregnant.

Not only will it help keep you healthy and your immune system healthy throughout your pregnancy, but it also plays an important role in your baby’s development.

A growing baby in the womb cannot make its own vitamin D, so it relies on you to have enough in your body for both of you. It allows your body to absorb calcium and phosphate to help your baby’s bones grow, especially in the second half of your pregnancy. 

Read more about the importance of vitamin D in pregnancy here.

The Department of Health England recommends that pregnant women receive 10 micrograms (µg) of vitamin D per day.13 

As this is difficult to obtain through diet and sunlight absorption alone, a supplement could be helpful to top levels up, especially for women who are pregnant during spring or winter and women with darker skin – as they won’t absorb as much sunlight.

Which vitamin D supplements are recommended for pregnant women?

It is likely you will be taking various supplements during your pregnancy, so it is important that it contains at least 10µg of vitamin D or you take an individual vitamin D3 10µg tablet.

A good pregnancy support supplement duo is folic acid and vitamin D, as folic acid (aka folate) is also very important for pregnancy.

Taking supplements formulated specifically for pregnant women makes sure that you do not risk taking too much vitamin A, which is not recommended during pregnancy.


  • Vitamin D is vital for pregnant women for their own health and the healthy development of their baby
  • Pregnant women should take 10 micrograms (µg) of vitamin D each day

Is vitamin D important for children and babies?

Yes, vitamin D is very important for growing little ones. It helps them maintain normal bones, teeth and muscle function and supports their normal immunity.

As vitamin D3 is made by our bodies when our skin is exposed to sunlight, living in less sunny climes (like the UK) can be an issue, especially in the darker and colder months.

In fact, the Department of Health England recommends that every child over the age of 1 takes a daily 10µg supplement, as well as implementing some fortified foods into their diet and spending time outside in the sunlight.14

Remember, we only need 10 minutes of direct sunlight on exposed and unprotected skin (arms, legs, hands and faces) to produce vitamin D.

To find out more, read our guide on vitamin D for children here. Babies under 1 need vitamin D too.

What type of vitamin D is best for children?

The government recommends a supplement of at least 10µg of vitamin D for children over the age of 1 and 8.5-10µg for babies under 1 year old.15

But getting children to take a supplement in tablet or capsule form is easier said than done – we get it! Thankfully, there are some child-friendly supplements out there.

Vitamin D drops for kids

No swallowing necessary – vitamin D drops are perhaps the sneakiest and most effective way to get your children and babies to take their vitamin D supplement.

Our Holland & Barrett Vitamin D3 Drops provide a perfect dose of vitamin D3 for children from 6 months to five years.

They are odour- and taste-free too, so you can mix them into your little one’s drinks and food – a completely incognito way of giving them their daily dose of vitamin D! Alternatively, just drop it onto their tongue – easy.

Chewable vitamin D for children

It looks like a sweet treat, it tastes like a sweet treat, no wonder your kids will probably prefer chewable vitamin D capsules!

We stock a wide range of chewable vitamin D, such as Wellkid Peppa Pig Vitamin D Soft Jellies which contain the exact level of Vitamin D recommended by the Department of Health England.16 

We also offer child and Teen Omega 3 Fish Oil Chewy Capsules with Vitamin D, so they get their all-important omega 3s along with their daily dose of vitamin D.


  • The UK government recommend vitamin D supplements for babies (8.5-10µg) and children (10µg)
  • There are some child-friendly supplements, like vitamin D drops and flavored chewable vitamins

Do babies need vitamin D?

Yes, babies under the age of 1 need vitamin D too.

Babies up to 1 year of age who are being breastfed should be given a daily supplement that contains 8.5 – 10 µg every day to make sure they are reaching recommended levels.17

This still applies if the breastfeeding mother is taking a supplement herself.

However, babies fed infant formulas will not need a vitamin D supplement if they are having more than 500ml of formula a day, as it will already by fortified with vitamin D and other nutrients.

The easiest way to provide breastfed babies with vitamin D is with vitamin D drops.

We have a Vitamin D3 Drop formula that is specifically designed for babies to take daily from birth until they are 12 months old.


  • Yes, babies who are being breastfed need 8.5-10µg vitamin D a day
  • Babies drinking infant formula won’t need to supplement as their milk will have been fortified with vitamin D already

Can vegans take a vitamin D supplement?

Vegans can be more susceptible to a vitamin D deficiency. The double whammy of not getting enough sunlight during the winter months and not being able to eat most of the food sources of vitamin D can make it a little more difficult.

However, even with meat, dairy and eggs off the menu, there are still natural vegan sources of vitamin D like mushrooms for vitamin D2 and lichen for vitamin D3.

As these are limited, a vitamin D supplement is recommended. Especially for vitamin D3 as we don’t think many vegans will be chowing down on some lichen!


  • Yes, and it is recommended that vegans take a supplement as their diet will be lacking in the important vitamin D
  • Vegans can make vitamin D3 from sunlight (like everyone) but this isn’t always available in the winter, so a supplement can help
  • Mushrooms and lichen contain natural sources of vitamin D3, but you would have to eat them every day

What type of vitamin D is best for vegans?

Here are some good sources of vitamin D that are suitable for vegans:

Vegan vitamin D capsules

Capsules are what most people imagine of when thinking of vitamin supplements. Alas, many vitamin D tablets and capsules contain a non-vegan source of vitamin D3, such as sheep lanolin or fish oils.

Don’t worry though, we have a solution! Our Mushroom Vegan Vitamin D Capsules contain 25µg of vitamin D2 in each capsule and you only have to take one a day.

Vegan vitamin D spray

If you want a vegan source of the faster-acting vitamin D3 or simply cannot stand taking tablets or capsules, a vitamin D spray could be for you.

Vitamin D sprays act incredibly fast as they bypass the digestive system and deliver vitamin D directly into the bloodstream.

Beware however, that not all vitamin D sprays are vegan, but BetterYou Dlux Vegan Vitamin D Spray is. Give it a go and see if it works for you. 

Vegan vitamin D drinks

Great news! You can now enjoy your daily dose of vitamin D while you enjoy a nice brew.

Check this delicious TEA+ Vitamin D Tea, which contains 10µg of vitamin D3.


  • There are vegan-friendly vitamin D capsules, vitamin D sprays, and even vitamin D teas!

What supplement should I take if I am at risk of low vitamin D?

The UK government recommendation stays at a minimum of 10µg vitamin D a day for vulnerable groups like the over 65s, people with darker skin and those who cover a lot of their skin for religious reasons, etc.

They just recommend that you take it all year round, and not just in autumn and winter.

We hope this guide has helped you determine which vitamin D supplement is best for you.

As always, this information cannot replace medical care, so please check with your doctor before trying any new supplements.


  • The UK government recommends that everybody considers taking a 10µg vitamin D supplement, especially during autumn and winter
  • Older people, people with darker skin and those who cover a lot of skin for religious reasons, etc. are recommended to take a supplement all year round
  • Check with your doctor if you have any concerns about your vitamin D supplement

Last updated: 11 January 2021


The advice in this article is for information only and should not replace medical care. Please check with your GP or healthcare professional before trying any supplements, treatments or remedies. Food supplements must not be used as a substitute for a varied and balanced diet and a healthy lifestyle.

Author: Donia HilalNutritionist

Joined Holland & Barrett: Jan 2018

Bsc in Nutrition, Registered Associate Nutritionist and Certification in Pre and Post Natal Nutrition

Donia started her career as a freelance nutritionist, later she joined Nestle as their Market Nutritionist to help support their healthier product range, before joining the team at Holland & Barrett in January 2018.

Donia has over 6 years experience as a Nutritionist and also works with clients on a one to one basis to support their goals which include weight loss, prenatal and postnatal nutrition and children’s health.

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