Vitamin d


Vitamin D deficiency

Diet and Nutrition

7 November 2023

It is recommended that children from the age of 1 and adults need 10 micrograms of vitamin D a day, particularly in the autumn and winter months when the sunlight hours are less than the spring and summer months.1

But what is vitamin D? And what happens if you don’t get enough?

Why do we need vitamin D?

Vitamin D helps our bodies absorb and use calcium and phosphate from our diet, minerals which are important for healthy bones, teeth and muscles.

While we know it’s important for building strong bones2, which can help ward off the bone thinning disease osteoporosis, vitamin D has other important roles too, including:

  • reducing the chance of heart disease,
  • helps to regulate blood pressure and inflammatory pathways,3
  • regulating mood and reducing depression4,
  • and helping to maintain a healthy immune system.5

What are the symptoms of vitamin D deficiency?

Symptoms can take time to develop if you’re deficient in vitamin D, for some it can be months for others it can be years. But it’s helpful to know the signs to look out for:

Bone health

If you’re lacking vitamin D, this can over time cause bones to become soft and weak, which can lead to bone deformities. Vitamin D plays a crucial role in calcium absorption and bone metabolism.

Low bone mineral density is an indication that your bones have lost calcium and other minerals. This places older adults, especially women, at an increased risk of fractures.

Immune health

Vitamin D has a role in supporting your immune system, and a lack of this vitamin can lead to frequent illnesses and infections.

Studies into the effect of vitamin D in the immune system, have shown that “avoidance of severe vitamin D deficiency improves immune health and decreases susceptibility to autoimmune diseases.”6

Mental health

Although more research is still needed, it’s thought that depression and anxiety are both linked to low levels of vitamin D.

Insufficient levels of vitamin D in depressive patients have been confirmed by many authors, but there have been conflicting results in subjects with anxiety disorders.7

Where can I get Vitamin D?

1. Being outside in the sun

Sunlight, specifically UVB rays, is the best source of vitamin D. In the UK, the sunlight is most effective between late March and September. 80–90% of vitamin D is derived from skin exposure to ultraviolet B radiation from sunlight, with the remaining 10–20% being derived from dietary sources.8

Over the autumn and winter months, sunlight is too weak to allow our skin to make enough vitamin D, which is why the government advises you take a supplement during this time.

There is no prescribed amount of sun exposure to produce the right amount of vitamin D as everyone is different. However, in the UK, 10 – 15 minutes of sun exposure to your bare skin – particularly to the forearms, hands and lower legs – should help build up your stores of vitamin D (it’s fat-soluble, so can be stored in fatty tissue).

Just take care not to burn, as redness is a sign of skin damage.

>Read more on our myths about sun damage

2. Dietary sources

Few foods contain vitamin D in sufficient quantities, so it can be difficult to get enough from your diet alone.

However, you’ll find small amounts in things like:

  • oily fish (e.g., herring, salmon, mackerel, and sardines),
  • liver,
  • egg yolks
  • and wild mushrooms.

It’s also added into foods such as cereals, margarine, reduced fat spreads, milk, and some almond milk products; look for ‘fortified’ on the label.

These foods should help make up part of your balanced diet.

>Try our Teriyaki Salmon Parcels recipe

3. Supplements

You should get sufficient vitamin D by following a healthy, well-balanced diet and by getting regular sun exposure. However, the Department of Health recommends taking a daily supplement of 10 micrograms during autumn and winter months (including pregnant and breastfeeding women).9

Who is at risk?

Those at greater risk of not getting enough vitamin D are strongly advised to take a daily vitamin D supplement throughout the year. These include:

  • small children, from one to four years-old,
  • older people, or those who are frail, housebound, or have limited sun-exposure,
  • people who wear skin concealing clothing,
  • people with dark skin who have higher melanin (skin pigment) levels, which slows vitamin D production,
  • or people with liver disease, malabsorption disorders, cancer and those needing steroids for treatment.

If you’re concerned you may not be getting enough vitamin D, talk to your pharmacist or GP about your symptoms.


  1. How much vitamin D do I need? - NHS
  2. Vitamin D deficiency in adults - NICE
  3. Role of Vitamin D - American Heart Association
  4. Vitamin D deficiency and depression in adults – National Library of Medicine
  5. Vitamin D and the immune system - National Library of Medicine
  6. Vitamin D’s Effect on Immune Function – National Library of Medicine
  7. Vitamin D in anxiety and affective disorders - National Library of Medicine
  8. Vitamin D deficiency in adults - NICE
  9. PHE publishes new advice on vitamin D – Gov.UK

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