Vitamin D is the back in the spotlight as we enter autumn and are faced with the dual threats of flu season and a significant rise in cases of COVID-19.
Refreshingly though, the buzz around vitamin D is not without foundation. Experts agree it’s the one vitamin everyone in the UK should be taking.
It’s hard to get enough from your diet or from the sun during the winter months and it plays a key role in immune health.
But how much should you take and who is most likely to be deficient? We’ve found wide variation in doses in high street supplements, with little coherence over what constitutes ‘high strength’.
We’ve delved into the dosage advice to help you navigate the supplement aisles and get the right amount for you.
Vitamin D sprays, gummies or tablets – what’s the best way to get your daily dose?
Why is vitamin D important?
Vitamin D keeps our immune systems functioning properly. This is especially important during the colder months when there are more bugs circulating.
It also enables our bodies to absorb calcium and phosphorous from the food we eat. These minerals are vital for healthy bones, teeth and muscles.
Coronavirus and vitamin D
There’s been a lot of buzz around vitamin D and coronavirus, but in June 2020 the National Institute for Health and Care Excellence (Nice) concluded that based on the existing research there was no evidence that taking vitamin D supplements could prevent or treat coronavirus – or other respiratory tract infections.
However, it’s well established that vitamin D supports the normal function of your immune system. So if you do catch coronavirus, your recovery might be easier if you’re not deficient.
More recently, a new US has study backed this up, finding that patients with low vitamin D levels suffered more complications with Covid-19.
Top vitamins and minerals for immune support – what the science says
How much vitamin D should you take?
Public Health England and the NHS recommend everyone takes a daily 10mcg supplement (this is sometimes labelled on supplements as 400 IU – International Units).
But with many retailers selling different variations of ‘high-strength’ vitamin D, from 25mcg to 100mcg, it can be tempting to reach for the highest number.
The NHS advises children aged 11 to 17 and adults not to take more than 100mcg of vitamin D a day as it could be harmful. Children between one and 10 should not take more than 50mcg a day.
Bear in mind high-dose vitamin D will be more expensive too. Unless you think you’re likely to be severely deficient, there’s no need to go to these upper limits.
High-dose vitamin D supplements
We’ve found vitamin D supplements containing up to 100mcg (4000 IU) both on the high street and online. This is 10 times the recommended daily dose and is the upper safety limit advised by the NHS.
If a blood test shows you are severely deficient your doctor might prescribe a short course of high-dose supplements (sometimes beyond this 100mcg limit), but they will supervise this and it’s usually only for a short time as high doses over a prolonged period can be harmful.
Is Vitamin D2 or D3 better for you?
There are two forms of vitamin D found in supplements: D2 (ergocalciferol) and D3 (cholecalciferol). D2 is produced by plants, whereas D3 is found in animals and is what we produce using sunlight.
Although their chemical structures are different, they are both absorbed in the small intestine.
A few studies have shown that vitamin D3 supplements are better at raising vitamin D levels compared with vitamin D2.
Who is most at risk of deficiency?
Some people are at higher risk of vitamin D deficiency than others. For people at risk of vitamin D deficiency the government advises taking a vitamin D supplement all year round.
Those at higher risk of low vitamin D levels include:
People with dark skin
People with dark skin have more melanin, which reduces the skin’s ability to make vitamin D. Studies show people with dark skin generally have lower vitamin D levels.
People who cover their skin
We can only make vitamin D if our skin is exposed to the sun. People who cover most of their skin in the sun are unable to make vitamin D.
The government recommends that breast-fed babies are given a daily supplement containing vitamin D (usually in the form of liquid drops). This is because it’s hard to get enough from breast milk alone.
Even once a baby is weaned, it’s hard to get enough vitamin D from food and we tend to keep babies out of the sun, so they’re unlikely to get enough from sun exposure.
Formula milk is fortified with vitamin D, so babies having more than 500ml a day of formula shouldn’t take a supplement.
People who rarely go outside
People who are frail, housebound or who live in a care home might not get out as much and as such have limited exposure to sunshine.
This also applies to people who work long days inside in shops or offices with little exposure to the sun.
Symptoms of vitamin D deficiency
It’s not easy to spot a vitamin D deficiency. Some people may feel tired or get aches and pains. Others may not suffer any symptoms of deficiency until it’s too late – for example bowed legs or poor growth in children.
Your doctor can carry out a blood test if you’re concerned, but everyone is advised to take a vitamin D supplement during the winter months.
Can you get enough Vitamin D from the sun or your diet?
Our bodies can make vitamin D from sunlight using the cholesterol in our skin cells. But in the UK, this can only happen between April and September as the sun isn’t strong enough in winter.
The government and World Health Organization (WHO) advise five to 15 minutes in the sun before 11am or after 3pm with forearms and lower legs uncovered, and without sunscreen is sufficient for most people to make enough vitamin D.
Beyond this, it’s important to wear sunscreen and cover up. You can find out more in our guide to vitamin D and sunscreen.
Between October and March, sunlight in the UK doesn’t contain enough UV radiation for us to make our own vitamin D, so we need to get it from other sources.
Some foods, such as oily fish, egg yolks, red meat and fortified foods contain vitamin D, but it’s hard to get enough from food alone.
For example, one boiled egg contains around 1.6 mcg of vitamin D and a salmon fillet contains around 13 mcg.
Mushrooms grown in sunlight or UV light also contain vitamin D – a 100g portion will contain around 5mcg, half your daily requirement.
Some breakfast cereals have vitamin D added to them, but a bowl of Fruit ‘n Fibre will only contribute 2.5mcg of vitamin D.
Fat spreads and some plant-based alternatives to milk also have vitamin D added to them, but again a portion won’t contribute much to your daily needs.
They’re best seen as an added bonus on top of a daily supplement.