Vitamin D (calciferol): foods, benefits & RDA

Vitamin D is the bones, muscles and teeth vitamin, although it also has a host of other benefits too. It regulates the amount of calcium and phosphate in the body, both needed for healthy bones and muscles.

What is vitamin D used for and does it really work?

This vitamin is essential for healthy bones, muscles, teeth as well as heart and nerves. A lack of vitamin D can lead to muscle weakness (leading to bone deformities), constipation and irritability. Vitamin D also has benefits for the immune system, and there have been reports suggesting vitamin D is useful in combatting coronavirus, although more research is needed.

Studies have found that people with low levels of vitamin D had a higher risk of heart attack, stroke and heart failure compared to people with high levels of vitamin D, with an NHS study finding that patients taking vitamin D alongside their heart medication had improved heart function.

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What’s the best way to take vitamin D?

This is the only vitamin that’s produced when your skin is exposed to sunlight. There are small amounts available in food too – oily fish, eggs, butter, cheese and leafy green vegetables, for example – but to ensure a healthy amount you either need to expose your skin to sunlight or take a supplement. In spring and summer, the majority of people can get enough vitamin D through sunlight on the skin and a healthy diet, but during autumn and winter people will need to rely on dietary sources. It can be hard to get the recommended 10mcg through diet alone.

As it’s relatively easy to become vitamin D deficient in northern climes, especially during winter when sunlight hours are dramatically reduced as is our skin’s exposure to sun, it is a good idea to supplement.

Vitamin D is important in relation to calcium and phosphorus in your body – it regulates quantities of both and so taking calcium supplements, for example, without also regulating your vitamin D intake, could mean that you’re not getting the benefit.

Where can I get vitamin D?

While sunscreen does block the UV rays that create vitamin D, even total sunblock allows some rays to pass through and so if you spend quite a lot of time outdoors chances are you are already getting enough even with sunscreen. However, you can also take a supplement of 10mcg (400IU) daily. If you are dark-skinned it is especially important to be aware of your vitamin D levels as you may not make enough via the sun.

How much time should you spend in the sun?

The amount of time needed in the sun is different for different skin types. You want to avoid getting burnt or turning pink, which can increase your risk of skin cancer. Research shows that 15 minutes a day when the sun is reasonably strong is enough for most fair-skinned people, as long as the skin doesn't go red.

The higher levels of melanin in darker skin makes it harder for those of African, African-Caribbean or south Asian ethnicity to get as much vitamin D so they will need to spend longer in the sun, with some studies showing darker skin needs as much as six times more sun exposure. Skin cancer is rarer in people with darker skin, but it is still an issue, particularly on the palms and soles of the feet.

To get the benefits of sunlight you need to be outside as your body can't produce vitamin D if you sit inside by a window. 

What are the side effects or contraindications of taking vitamin D?

As vitamin D influences calcium levels, it’s important not to take more than the recommended dosage. Too much can lead to nausea and vomiting as a result of excessive calcium levels via the vitamin D.

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