Unlike other vitamins, your body can actually make vitamin D on its own – all it needs is sunlight. That's why it's often called the "sunshine vitamin". During the darker months, a supplement is a simple way to help keep your levels healthy, supporting the normal function of your bones, muscles and immune system.
What is vitamin D and why do you need it?
Interestingly, vitamin D isn't technically a vitamin at all – it's more of a hormone. Your body produces it when UV rays hit your skin, which breaks the traditional rules for vitamins (they're usually nutrients you have to get from food). It's a unique nutrient, and your body only needs small amounts of it.
There are different forms of vitamin D, including D3 (from sunlight and animal sources) and D2 (from plants) – and if you've ever wondered how D3 and K2 work together, we cover that in Vitamin D3 vs K2: which supplement do you need?. More than 90% of our body's vitamin D comes from sunlight alone. Its most important job is helping to regulate the amount of calcium and phosphorus in the body – which is exactly why it matters so much for you. Vitamin D contributes to the maintenance of normal bones, teeth and muscle function, and to the normal function of the immune system. It also plays a role in normal cell division and helps the body absorb and use the calcium it needs.
What are the best sources of vitamin D?
The best source of vitamin D is sunshine – when UV rays hit your skin, your body makes it naturally. From late March to September, most people can produce all the vitamin D they need just by spending time outdoors (balance is key – about 10 minutes of midday sunlight often does the job).
But "sunny days" and "reliable weather" aren't exactly our strong suit in the UK. Between October and early March, the sun's rays aren't strong enough for your body to make vitamin D, which is why supplements are so widely recommended over winter in particular.
It's worth knowing that your skin can't produce vitamin D from sunlight shining through a window, and sunscreen blocks the UVB rays needed to make it. So topping up your levels properly means actually getting outdoors.
You'll also find small amounts of vitamin D in oily fish like salmon, as well as red meat, egg yolks, liver and fortified foods. But it's nearly impossible to get enough from food alone (you'd need to eat roughly 25 eggs to hit your daily target from eggs alone!). For most people, sunlight and supplements are the primary sources.
Should I take a vitamin D supplement?
For most people in the UK, the answer is yes – at least during autumn and winter. The NHS recommends that everyone consider taking a daily supplement of 10 micrograms (400 IU) during the darker months, when your body can't make vitamin D from sunlight.
Some groups should take a supplement year-round, including babies, children aged 1–4, people who aren't often outdoors, and those who cover most of their skin for cultural or religious reasons, as well as women who are pregnant or breastfeeding.
Because darker skin is rich in melanin, it's naturally better at blocking UV rays – but that also makes it harder for your body to make vitamin D from the sun. If you have darker skin, it's recommended that you take a vitamin D supplement daily, and not just during winter.
If you're unsure whether you're getting enough, it's worth speaking with a healthcare professional. Otherwise, a daily supplement is a simple way to maintain healthy levels. Vitamin D supplements come in both pill and liquid form.
Explore further
Want to go deeper on vitamin D? These pieces from our Discover blog pick up where this leaves off:
- Vitamin D3 vs K2: which supplement do you need? – how the two forms work together and how to choose.
- Vitamin D deficiency: symptoms to know – the signs that your levels might be running low.
Explore our range of vitamin D supplements to support normal bones, muscles and immune function year-round.
