This week I’m going to start a new series of posts called ‘nutrient nuggets’. I thought it would be helpful to give you snippets of information about a particular nutrient, mineral or vitamin.
So, as it’s summer…where better to kick off than with vitamin D?
Why do we need vitamin D?
Vitamin D helps regulate the amount of calcium and phosphate in the body, these are all are used in combination to help make our bones strong and healthy. Vitamin D has many other important roles in the body, including helping maintain muscular strength, immune function and reducing inflammation. Vitamin D also plays an essential role in cell growth; where cells become specialised for a specific function.
Where do we get it from?
The majority (80-90%) of vitamin D is obtained from the sun; when sunlight hits the skin, it causes a reaction under our skin which produces vitamin D.
There are only a couple of dietary sources of vitamin D. Good sources are; oily fish (herring, mackerel, salmon, sardines etc), eggs and fortified fat spreads (required by UK law to contain vitamin D). Some yoghurts and breakfast cereals are also fortified with vitamin D.
How much do we need?
Exposing your face and forearms to the sun a few times a week should be sufficient to maintain good vitamin D levels through the summer. (Remember to cover up and use suncream when out for extended periods and at the hottest times of the day to reduce the risk of skin damage and skin cancer). However, through the winter, it is not possible for our bodies to use sunlight to make vitamin D and this can lead to low levels. It is recommended that everyone in the UK consider taking a 10 microgram (μg) vitamin D supplement from October to March.
Certain population groups such as pregnant women, babies, people who cover their skin when outdoors and those with darker skin are at increased risk of vitamin D deficiency. For these groups, a daily 10 microgram (μg) vitamin D supplement is recommended throughout the year.
The Department of Health in the UK recommends that pregnant and breastfeeding mums should also take a 10μg supplement of vitamin D to ensure she is meeting her nutritional requirements and to help build adequate nutrient stores. Breastfed babies and children aged 1 to 4 years should also take a daily vitamin D supplement (up to 10 micrograms (μg)). Formula fed babies should not take vitamin D unless they are having less than 500ml formula a day as formula is fortified with vitamin D.
What if we don’t get enough?
Early signs of deficiency can be fatigue, muscle aches/weakness and bone pain. A lack of vitamin D over the longer term can cause a bone deformity disorder in children called rickets. Rickets causes the bones to become soft, tender and weak. It can also cause problems with developing teeth. In adults, a similar bone softening condition called osteomalacia can occur.
If you are concerned about your vitamin D levels, you should speak to your doctor, or ask to be referred to a dietitian.
What if we get too much?
Too much vitamin D can upset the balance of calcium and phosphate, provoking the removal of calcium from bones, weakening them. This imbalance can also lead to excess calcium being absorbed rather than being excreted. Excess calcium can be deposited in the kidneys and cause damage.
Given the low amount of vitamin D in most diets, it is most likely vitamin D in excess would occur as a result of taking too higher dose of supplement. The NHS state adults should not take any more than 100 micrograms (μg) of vitamin D per day, children age 1 to 10 years no more than 50 micrograms (μg) and babies less than 1 year no more than 25 micrograms (μg) daily.
What can we do to prevent deficiency diseases?
Rickets and osteomalacia can be prevented by eating a healthy, balanced diet incorporating some sources of vitamin D and taking supplements as recommended above. The NHS also advises 20-30 minutes of sun on the face and forearms a couple of times a week. Please note: You should still use suncream to protect your skin.
Where can I find out more?
NHS: Vitamin D
Find out more about rickets on the NHS Choices website, here.
The Journal of Family Healthcare have a great article detailing causes, prevalence and prevention of rickets.
[Updated May 2020]