Vitamin D plays several key roles. Most importantly, vitamin D helps your body absorb and regulate the minerals calcium and phosphate from the food you eat.
Vitamin D food sources
Good food sources of vitamin D include:
- Oily fish, including salmon and sardines
- Fortified spreads
- Fortified breakfast cereal
- Powdered milk
Vitamin D uses
Vitamin D is important for people with osteoporosis. Studies show that calcium and vitamin D together can increase bone density in postmenopausal women. Vitamin D also helps with other disorders associated with weak bones, such as rickets.
Most people get enough vitamin D from their diet and from some exposure to sun in the summer months. However, some groups are at an increased risk of having low levels of vitamin D - called vitamin D deficiency - and may need supplements after taking medical advice. These groups include:
- Pregnant and breastfeeding women
- Babies and young children under five
- People aged 65 and over
- Those who are not exposed to the sun often, such as people who are housebound or confined indoors for long periods or who always cover-up outdoors.
- People with darker skin such, such as African, African-Caribbean and South Asian backgrounds.
The Department of Health recommends that the following groups take a vitamin D supplement:
- All pregnant and breastfeeding women should take a daily supplement containing 10 micrograms of vitamin D
- All babies and young children aged six months to five years should take a daily supplement containing vitamin D in the form of vitamin drops (7.0-8.5 micrograms of vitamin D per day). Babies fed infant formula will not need vitamin drops until they are receiving less than 500ml (about a pint) of infant formula a day, as formula is fortified with vitamin D.
- Breastfed infants may need to receive drops containing vitamin D from one month of age if their mother has not taken vitamin D supplements throughout her pregnancy.
- People 65 and over and those who are not exposed to much sun light should take a daily supplement containing 10 micrograms of vitamin D.
Supplements of vitamin D come in various forms, including tablets, and for children, special drops. Under the Healthy Start scheme, pregnant women can get free supplements which contain vitamin D.
Vitamin D deficiency may cause hormone problems, muscle weakness and pain, and other symptoms.
Studies have found prescription-strength vitamin D lotions helpful in treating psoriasis. Vitamin D has also been studied for other conditions ranging from cancer prevention to high blood pressure, but the evidence is unclear.
How much vitamin D does a person need?
While too little vitamin D can cause health problems, too much is also harmful. Taking too much vitamin D over a long period can cause more calcium to be absorbed than the body can cope with. That can cause kidney problems and actually soften and weaken bones rather than maintain bone health.
The NHS says is a person decides to take vitamin D supplements, 25 micrograms (0.025mg) or less a day is unlikely to cause any harm.
You cannot get too much vitamin D from being in the sun, but it is important to get the balance right with sun exposure. Your body needs enough sun in the summer months to make vitamin D, but not so much that the skin burns as that increases the risk of skin cancer.