Hand holding a vitamin D supplement capsule in front of the sun.
Hand holding a vitamin D supplement capsule in front of the sun.

How vitamin D helps the body

Vitamin D is a fat-soluble vitamin that’s responsible for helping your body regulate the absorption of calcium and phosphorous. It also helps contribute to a normal immune system function (1).

When your skin is directly exposed to sunlight, your body should naturally produce enough vitamin D. But as we enter autumn and winter, you’ll find you’re not exposed to the sunlight as much and may need to get vitamin D from other sources.

Vitamin D deficiency

Vitamin D deficiency is most common in people over the age of 65 and those with a darker skin tone. Vitamin D deficiency causes include not getting enough of the important vitamin through sunlight and in your diet, or that your body just isn’t absorbing or using vitamin D.

What are the signs you need vitamin D?

  • Bone pain
  • Fatigue
  • Muscle weakness
  • Depression

A severe lack of vitamin D in children can lead to bone deformities such as rickets. It can also weaken bones in adults and cause a condition known as osteomalacia, or soft bones.

Can vitamin D affect sleep?

A cross-sectional study reported that vitamin D deficiency correlated with poorer sleep quality. The study suggested a potential role for vitamin D in maintaining healthy sleep (2).

Our blog on how to sleep and why we need it delves into the causes of bad sleep and provides some natural solutions.

Sources of Vitamin D

In the UK, you should be able to make all the vitamin D you need from direct sunlight on your skin and a balanced diet from about late March to the end of September. But when it comes to preventing or treating a vitamin D deficiency, you may take supplements between October and early march to ensure adequate levels of the vitamin in your blood.

Vitamin D supplements

The NHS recommends those at high risk of not getting enough vitamin D, all children aged 1 to 4, and all babies (unless they're having more than 500ml of infant formula a day) should take a daily supplement throughout the year. So, what are the options available to you?

  • Capsules
  • Liquid
  • Sprays
Vitamin D supplements in an eco-friendly bowl.
Vitamin D supplements in an eco-friendly bowl.

How vitamin D helps the body

When should I take a vitamin D supplement?

Government advice is that everyone should consider taking a daily vitamin D supplement during the autumn and winter. Current research suggests you can take your vitamin D supplement at any point in the day you prefer, however more research is being done into the effects of vitamin D being taken closer to bedtime.

Vitamin D dosage

Babies up to the age of 1 year: 8.5 to 10 micrograms a day.

Children from the age of 1 year and adults: 10 micrograms a day. This includes pregnant and breastfeeding women, and people at risk of vitamin D deficiency.

A microgram is 1,000 times smaller than a milligram (mg). The word microgram is sometimes written with the Greek symbol μ followed by the letter g (μg).

Sometimes the amount of vitamin D is expressed as International Units (IU). 1 microgram of vitamin D is equal to 40 IU. So, 1 micrograms of vitamin D is equal to 400 IU.

Vitamin D foods

What food is highest in vitamin D?

  • Oily fish – such as salmon, sardines, herring and mackerel
  • Red meat
  • Liver
  • Egg yolks
  • Fortified foods – such as some fat spreads and breakfast cereals

What fruit is rich in vitamin D?

Unfortunately, there are no fruits containing high levels of vitamin D. Fortified orange juice is sold containing vitamin D.