But we get most of our vitamin D from sunlight on our skin. This is because the vitamin forms under the skin in reaction to sunlight. The best source is summer sunlight but remember, if you're out in the sun, take care not to burn.
Liver and liver products are also good sources of vitamin D, but they are also a rich source of vitamin A. So if you already eat them every week, you might want to choose not to have them more often.
How much do I need?
Vitamin D is a fat-soluble vitamin. This means you don't need it every day because any of the vitamin your body doesn't need immediately is stored for future use.
Most people should be able to get all the vitamin D they need from their diet and by getting a little sun.
However, if you are pregnant or breastfeeding you should take 10 micrograms (0.01 mg) of vitamin D each day.
Older people should also consider taking 10 micrograms (0.01 mg) of vitamin D each day.
You might be particularly short of vitamin D, and so might want to think about taking 10 micrograms (0.01 mg) of vitamin D each day, if you:
are of Asian origin always cover up all your skin when you're outside rarely get outdoors eat no meat or oily fish If you aren't getting enough vitamin D, you might be more at risk of some of the harmful effects of too much vitamin A.
Ask your GP if you want more information.
What does it do?
Vitamin D has a number of important functions. For example it helps regulate the amount of calcium and phosphate in the body, and calcium and phosphate are needed to help keep bones and teeth healthy.
What happens if I take too much?
Taking high doses of vitamin D for long periods of time could weaken your bones.
What is our advice?
Most people should be able to get the amount they need by eating a varied and balanced diet and by getting some sun. But if you decide to take vitamin D supplements it's a good idea not to take too much because this could be harmful.
Taking 25 micrograms (0.025 mg) or less of vitamin D supplements a day is unlikely to cause any harm.