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Everything you need to know about vitamin D deficiency

Phil Day: Superintendent Pharmacist | minute read

Research has found that approximately 1 in 6 adults in the UK and almost 1 in 5 children have low vitamin D levels, suggesting many of us may be risking unwanted symptoms associated with a vitamin D deficiency. In this article, we explore what vitamin D does for the body, what side effects low vitamin D levels can cause, who’s most at risk of vitamin D deficiency, and how you can ensure you’re getting the amount you need all year round.

What is vitamin D and why do we need it?

Vitamin D is an essential nutrient our bodies need to function at their best. It helps the body absorb calcium and phosphate, which are required to support healthy bones, muscles, and teeth. Approximately 90% of our recommended daily vitamin D intake comes from sunlight during spring and summer. Exposure to UVB rays from the sun triggers our skin to make vitamin D. From late October to early March, it may be possible to obtain the vitamin D we need from food sources such as red meat, oily fish, animal livers, and egg yolks. The choice of food sources containing vitamin D however is limited, and if you follow a specialist diet that doesn’t include animal products, this isn’t an option. You might want to consider taking a vitamin D supplement throughout winter. We talk more about vitamin D supplements later in this article.

What happens if I don’t get enough vitamin D?

Although a low level of vitamin D often doesn’t cause any symptoms, it can contribute to tiredness and feeling generally run down. In some cases, vitamin D deficiency can lead to a condition that affects the bones. This is known as rickets in children and osteomalacia in adults. It’s uncommon in the UK, but symptoms in children include bone pain (sometimes apparent by a child’s reluctance to move around), tooth decay or a delay in teeth forming, skeletal issues like bowing legs, limited growth and development, and a higher risk of bone fractures. Because vitamin D helps regulate calcium in the body, children who are deficient may also have low levels of calcium. This can lead to muscular symptoms such as cramps and spasms, and a tingling sensation in the hands and feet. Adults with osteomalacia may experience similar symptoms to children with rickets. If left untreated, long-term (chronic) vitamin D deficiency can increase the risk of developing osteoporosis.

Who is most at risk of vitamin D deficiency?

Although anyone can experience low vitamin D levels, there are some groups who are at increased risk of deficiency. These include:

  • Infants and children under 4

  • People who have limited exposure to sunlight (either as a result of not spending much time outdoors or wearing clothing that covers most of the skin when outside)

  • Those with a medical condition that reduces the absorption of nutrients from food

If you’re concerned about low vitamin D levels, talk to a pharmacist or your GP. Your doctor can organise a blood test to check your levels and advise you about treatment if your results indicate a deficiency.

How can I make sure I’m getting enough vitamin D?

The best way to get your recommended vitamin D intake from March to October is to spend time outdoors in daylight. It’s essential to protect yourself from the sun’s harmful UV rays, especially in strong sunlight. Our sun care FAQs guide offers helpful tips to stay sun safe. If you’re not able to spend much time outdoors and your diet includes animal products, oily fish including mackerel, salmon, and sardines offer a natural source of vitamin D. Red meat is another naturally occurring source. However, this should be eaten in moderation as part of a varied diet. You’ll also find some foods and drinks such as specialist cereals, milks, and flavoured waters that are fortified with vitamin D.

Vitamin D supplements are recommended for everyone in the winter months (October to March) when the sun isn’t strong enough to trigger our bodies to make it. The NHS advises that a supplement containing 10 micrograms (µg) of vitamin D is sufficient for adults, including those who are pregnant or breastfeeding. The advice from the Department of Health and Social Care also recommends that children between the ages of 1 and 4 are given a 10-microgram vitamin D supplement throughout the year.

For infants under the age of 1 who are breastfed or given less than 500ml of formula per day, a vitamin D supplement is also advised. Your healthcare practitioner will most likely discuss this with you during your pregnancy, or you can find out more in this NHS guide outlining vitamin requirements for infants. If your baby is bottle-fed with formula, this will be fortified with all the vitamin D they need, so a supplement isn’t required. If you’re an expectant or new mum, you might be eligible for free vitamin supplements on the NHS through its Healthy Starts scheme. You can learn more about the scheme, including whether you qualify for extra support and how to apply, at the Healthy Starts website.

You can also buy vitamin D supplements from trusted brands such as Centrum, Haliborange, and Vitabiotics at our online pharmacy shop.

To help you get to grips with all the nutrients our bodies need daily, we’ve put together these vitamins A-Z and minerals A-Z guides that list what they are, why we need them, and what foods offer the best source of each.