Vitamin D helps regulate the amount of calcium and phosphate in the body.
These nutrients are needed to keep bones, teeth and muscles healthy.
A lack of vitamin D can lead to bone deformities such as rickets in children, and bone pain caused by a condition called osteomalacia in adults.
Good sources of Vitamin D
From about late March/early April to the end of September, most people should be able to get all the Vitamin D they need from sunlight.
The body creates Vitamin D from direct sunlight on the skin when outdoors.
But between October and early March we don't get enough Vitamin D from sunlight.
Vitamin D is also found in a small number of foods. Sources include:
Oily fish – such as salmon, sardines, herring and mackerel
Red meat
Liver
Egg yolks
Fortified foods – such as most fat spreads and some breakfast cereals
In the UK, cows' milk is generally not a good source of Vitamin D because it isn't fortified, as it is in some other countries.
Another source of Vitamin D is dietary supplements.
How much Vitamin D do I need?
Babies up to the age of 1 year need to take between 8.5 to 10 micrograms of Vitamin D a day.
A microgram (mc