Vitamin D helps regulate the amount of calcium and phosphate in the body.
These nutrients help keep bones, teeth and muscles healthy.
A lack of vitamin D can lead to bone deformities such as rickets in children.
Adults can have bone pain caused by a condition called osteomalacia.
In Ireland, studies have shown that adults have low levels of vitamin D.
Good sources of vitamin D
From about late March 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 do not get enough vitamin D from sunlight.
Vitamin D is also found in a small number of foods.
- oily fish – such as salmon, sardines, herring and mackerel
- red meat
- egg yolks
- fortified foods – such as some fat spreads and breakfast cereals
Another source of vitamin D is dietary supplements.
How much vitamin D you need
Babies under 12 months need 5 micrograms of vitamin D as a supplement every day from birth if they are:
- have less than 300mls or 10 fluid oz (ounces) of infant formula a day
You should stop giving your child formula milk when they reach 1 year of age.
Children aged 1 to 4 need 5 micrograms of vitamin D as a supplement every day for a few months each year. Give this from Halloween (October 31) to St Patrick’s Day (March 17).
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 10 micrograms of vitamin D is equal to 400 IU.
Taking vitamin D supplements
Adults and children over 4 years old
During the autumn and winter, you need to get vitamin D from your diet because the sun is not strong enough for the body to make vitamin D.
It's difficult for people to get enough vitamin D from food alone. So you can take a daily supplement containing 10 micrograms of vitamin D during autumn and winter.
Between late March to the end of September, most people can get all the vitamin D they need through sunlight on their skin and from a balanced diet.
You do not have to take a vitamin D supplement during these months.
You can get Vitamin D supplements from pharmacies. They are available as a tablet, including a chewable tablet and a tablet that dissolves in your mouth.
You should take vitamin D supplements with a large meal to help your body absorb the vitamin D.
People at risk of vitamin D deficiency
Some people will not get enough vitamin D from sunlight because they have very little or no sunshine exposure. Or, they do not get enough vitamin D from sunlight.
You may need to take a daily supplement containing 10 micrograms of vitamin D throughout the year if you:
- are not often outdoors – for example, if you're frail or housebound
- are in an institution like a care home
- usually wear clothes that cover up most of your skin when outdoors
- have a dark skin tone
Effects of taking too much vitamin D
Taking too many vitamin D supplements over a long time can cause too much calcium to build up in the body (hypercalcaemia). This can weaken the bones and damage the kidneys and the heart.
If you choose to take vitamin D supplements, 10 micrograms a day is enough for most people.
Do not take more than 100 micrograms (4,000 IU) of vitamin D a day as it could be harmful. This applies to adults, the elderly, and children aged 11 to 17 years.
Children aged 1 to 10 years should not have more than 50 micrograms (2,000 IU) a day. Infants under 12 months should not have more than 25 micrograms (1,000 IU) a day.
Some people have medical conditions that mean they may not be able to safely take as much. If in doubt, talk to your GP.
Follow the advice of your GP if they recommend that you take a different amount of vitamin D.
You cannot overdose on vitamin D through exposure to sunlight. But always remember to cover up or protect your skin if you're out in the sun for long periods to reduce the risk of skin damage and skin cancer.
Content supplied by the NHS and adapted for Ireland by the HSE