What is vitamin D deficiency?

Vitamin D deficiency means there isn't enough vitamin D in your body. Vitamin D is an essential vitamin that your body needs for healthy bones and muscles. Vitamin D deficiency is a common worldwide problem.

Vitamin D helps our body absorb calcium and phosphorus from the gut (bowel) and this is essential for healthy bones and to allow our muscles to function properly. Therefore, vitamin D deficiency mainly causes problems with bones and muscles.

Vitamin D is made in the skin but this needs adequate exposure to sunlight. It can also be obtained from foods (particularly fortified foods) and vitamin D supplements.

Vitamin D has to be converted to an active form, which occurs in the liver and kidneys. This is why some types of liver and kidney disease can affect the way the body handles vitamin D, and so cause vitamin D deficiency.

Vitamin D also plays a role in your nervous system and immune system.

Why is vitamin D so important?

Getting enough vitamin D is crucial for healthy bones and teeth. In children, being deficient in vitamin D can lead to a condition called rickets, where your bones are weak and soft and can become deformed (with bow legs). In adults, low levels of vitamin D can increase your risk of osteoporosis, or thinning of the bones. This makes you much more prone to breaking a bone.

But vitamin D is important for much more than bone health. Vitamin D may play a role in:

• Improving muscle strength.
• Keeping your immune system strong, helping to fight off infections.
• Protecting you against certain cancers.
• Reducing your risk of falls.
• Helping to stave off depression and low mood.
• Keeping your energy levels up.

How much vitamin D do I need?

Vitamin D is sometimes known as the 'sunshine vitamin': the natural type of vitamin D is produced in your skin when you're exposed to sunlight.

In the UK, sunshine isn't strong enough to allow you to make your own vitamin D in winter. So it's now recommended that everyone over 1 year old take 10 micrograms (400 International Units) a day from October to March.

Certain groups of people are at higher risk of low vitamin D. It's advised that you take a vitamin D supplement of 10 micrograms (400 International Units) a day all year round if you:

• Are pregnant or breastfeeding.
• Are aged 1-4 years.
• Are over 65 (older adults are less efficient at producing vitamin D).
• Have little exposure to sunlight, because you:
• Are housebound.
• Are confined indoors for long periods.
• Cover your skin for cultural reasons.
• Have darker skin, for example if you are of African, African-Caribbean or South Asian origin (because your body is not able to make as much vitamin D from sunlight).

In addition, your doctor may recommend that you take a supplement all year round if you have certain gut (bowel), kidney or liver diseases.

Babies from birth to 1 year old should have a supplement in the form of vitamin D drops of 8.5 to 10 micrograms a day. Babies having 500 ml or more of formula milk per day do not need supplements, as formula milk already has vitamin D added.

You can buy vitamin D dietary supplements at pharmacies. In the UK they are also available on prescription to certain groups of people.

Vitamin D deficiency symptoms

Many people have no vitamin D deficiency symptoms or may complain of only vague ones such as tiredness or general aches. Because symptoms of vitamin D deficiency are often very nonspecific or vague, the problem is often missed. The diagnosis is more easily reached in severe deficiencies with some of the classical (typical) symptoms and bone deformities.

Vitamin D deficiency symptoms in babies

Babies with severe vitamin D deficiency can get:

• Cramps (muscle spasms).
• Fits (seizures).
• Breathing (respiratory) difficulties.

These problems are related to consequent low levels of calcium.

Vitamin D deficiency symptoms in children

• Children with severe deficiency may have soft skull or leg bones. Their legs may look curved (bow-legged). They may also complain of bone pains, often in the legs, and muscle pains or muscle weakness. This condition is known as rickets.
• Poor growth. Height is usually affected more than weight. Affected children might be reluctant to start walking.
• Tooth delay. Children with vitamin D deficiency may be late teething, as the development of the milk teeth has been affected.
• Irritability in children can be due to vitamin D deficiency.
• Children with vitamin D deficiency are more prone to infections. Breathing symptoms can occur in severe cases. Breathing can be affected because of weak chest muscles and a soft rib cage.
• When rickets is very severe, it can cause low levels of calcium in the blood. This can lead to muscle cramps, fits and breathing difficulties. These need urgent hospital treatment.
• Rarely, an extremely low vitamin D level can cause weakness of the heart muscle (cardiomyopathy).

Vitamin D deficiency symptoms in adults

• Some people complain of a general tiredness, vague aches and pains and a general sense of not being well.
• In more severe deficiency (known as osteomalacia), there may be more severe pain and also weakness. Muscle weakness may cause difficulty in climbing stairs or getting up from the floor or a low chair, or can lead to the person walking with a waddling pattern.
• Bones can feel painful to moderate pressure (often more noticeable in the ribs or shin bones). Not uncommonly, people have a hairline fracture in the bone which is causing tenderness and pain. Bone pain often also occurs in the lower back, hips, pelvis, thighs and feet.

What causes vitamin D deficiency?

A vitamin D deficiency may happen because:

• Your body has an increased need for vitamin D.
• Your body is unable to make enough vitamin D.
• You don't have enough vitamin D in your diet.

You have an increased need for vitamin D

Growing children, pregnant women, and breastfeeding women need extra vitamin D because it is required for growth. So, vitamin D deficiency is more likely to develop in the following groups of people:

• Pregnant or breastfeeding women. Vitamin D deficiency is even more likely to develop in women who have had several babies with short gaps between pregnancies.
• Breastfed babies whose mothers are lacking in vitamin D, or with prolonged breastfeeding, as there is little vitamin D in breast milk.

Your body is unable to make enough vitamin D

This can occur for various reasons:

• People who get very little sunlight on their skin are at risk of vitamin D deficiency. This is more of a problem in the more northerly parts of the world (including the UK) where there is less sun. In particular:
  • People who stay inside a lot. For example, those in hospital for a long time, or housebound people.
  • People who cover up a lot of their body when outside.
  • The strict use of sunscreen may increase the risk of vitamin D deficiency, particularly if high sun protection factor (SPF) creams (factor 15 or above) are used. However, there is no evidence that the normal use of sunscreen does actually cause vitamin D deficiency in real life. Everyone, especially children, should always be protected from the harmful effect of the sun's rays. See the separate leaflet called Sun and Health for more information.
• Elderly people are unable to produce as much vitamin D. This leaves older people more at risk of vitamin D deficiency.
• People who have darker skin are not able to make as much vitamin D.
• Some medical conditions can affect the way the body handles vitamin D. People with Crohn's disease, coeliac disease, and some types of liver and kidney disease, are all at risk of vitamin D deficiency.
• Rarely, some people without any other risk factors or diseases become deficient in vitamin D. It is not clear why this occurs. It may be due to a subtle metabolic problem in the way vitamin D is made or absorbed. So, even some otherwise healthy, fair-skinned people who get enough sun exposure can become deficient in vitamin D.
• Vitamin D deficiency can also occur in people taking certain medicines. Examples include: carbamazepine, phenytoin, primidone, barbiturates and some anti-HIV medicines.

Not enough dietary vitamin D

Vitamin D deficiency is more likely to occur in people who follow a strict vegetarian or vegan diet, or a non-fish-eating diet.

How common is vitamin D deficiency?

A lack of vitamin D is very common. One survey in the UK showed that about 1 in 5 adults and about 1 in 5 children in the UK have low vitamin D levels. More people have low vitamin D levels in the winter and spring because of less exposure to sunlight.