Do you really need to supplement vitamin D in summer?

Despite the longer days – and the more chances to be outside that summer brings – many of us living here in the UK still don't get enough vitamin D (the essential vitamin produced by the body when it is exposed to sunlight).

According to the NHS, that amount is around 10 micrograms (400 IU) of vitamin D per day for everyone over the age of one. While it's possible to get this quantity from the sun between April and September, in reality that can't always happen – nor is it considered safe by some. Ergo, supplementation is commonly advised.

But to better understand the importance of vitamin D – and the best ways to get sufficient amounts and when – we spoke to the experts for the facts.

What is vitamin D and why is it important?

"Vitamin D is crucial for keeping your body running smoothly, and not getting enough can lead to serious health issues," explains health expert Dr. Naomi Newman-Beinart (PhD). "Many people in the UK are lacking in this important vitamin, which is key for healthy bones and teeth, your mood, and supporting your immune system." There is also some evidence to show that vitamin D could help prevent some cancers, cardiovascular disease and multiple sclerosis.

How do you know if you're deficient in vitamin D?

"Deficiency can be assessed via a simple blood test – if you suspect you may be deficient ask your GP to test you or get tested privately," says the nutritionist Kim Pearson. "Common symptoms of deficiency include lower-back pain, muscle weakness, muscle aches, and fatigue; but you can be deficient and experience no symptoms at all."

How much vitamin D do you need?

"According to the NHS, everyone over the age of one needs about 10 micrograms (400 IU) of vitamin D a day, with the safe upper limit for vitamin D being 100μg (4,000 IU) a day," confirms Dr. Newman-Beinart.

"While it's especially important to take vitamin D during the darker months, some people should consider supplementing all year round —especially if they spend most of their time indoors, have darker skin, are over the age of 65 or under the age of five, are pregnant, breastfeeding, or follow a vegan diet."

Can you get enough vitamin D from your diet?

"Foods such as oily fish (like salmon and mackerel), red meat, liver, egg yolks, and fortified foods (such as some cereals and spreads) do contribute to our vitamin D intake," says Dr. Newman-Beinart. "But while some foods are rich in vitamin D, dietary sources alone are often insufficient to meet the recommended levels." For people who don’t eat these foods nor get regular sunshine, "it may be worth considering a vitamin D supplement all year round," she feels.

How does SPF affect your vitamin D levels?

"We all need some UV for our bodies to make vitamin D – but most people can make enough vitamin D without spending a long time in strong sun or risking sunburn," says Sarah Williams, Cancer Research UK's health information manager.

Dr. Newman-Beinart explains: "While essential for protecting our skin from harmful UV rays, sunscreen can also impede vitamin D synthesis. SPF works by blocking UVB rays, the type of sunlight responsible for stimulating vitamin D production in the skin." But this doesn't mean you should skip sunscreen, the experts unanimously agree. "Instead, manage your sun exposure wisely. For instance, brief periods of sun exposure (about 10-15 minutes) without sunscreen can be sufficient for vitamin D production, followed by sunscreen application to protect against prolonged exposure." Or, you could rely on supplementation entirely.

What's the best way to supplement vitamin D?

BetterYou D3000 IU Oral Spray

£6.12

The pharmacist specialising in vitamins, Shabir Daya, recommends taking the BetterYou D3000 IU Daily Oral Spray in the winter months and then swapping to the brand's 1000 IU Daily Oral Spray throughout the summer. And Dr. Newman-Beinart concurs, "because BetterYou uses science-backed intra-oral spray technology that delivers the active ingredient through the cheek (buccally) rather than relying on absorption through the digestive system".

The mouth is an excellent receptor for supplements, she says, "because of its soft, absorbent tissue and because it is so close to the body’s vein system".