Vitamin D has been all over the news, with so much information about, and some misinformation, it is easy to get a bit confused about what you should be doing and why. I hope this blog helps explain what the current recommendations are in the UK, and why they exist.

Vitamin D is produced naturally when our skin is exposed to ultraviolet-B radiation from the sun. When it penetrates the skin it sets off a chain of events resulting in the production and circulation of vitamin D in our bodies.

You need vitamin D to control the amount of calcium and phosphate in our bodies required for strong bones and healthy teeth. When there is vitamin D deficiency the body can’t absorb calcium from the intestines and more calcium is excreted from the kidneys. Yet having the right amount of calcium in your blood is crucially important and highly regulated so your body has to get it from somewhere and when vitamin D can’t supply it, another hormone called PTH jumps in and draws calcium from your bones. Eventually, this results in rickets in children and osteomalacia, painful bones, in adults.

But Vitamin D does so much more than that! It controls over 200 cells and deficiency has been associated with auto-immune conditions and some cancers, SACN (2007).

The sun, not food, is the main source of vitamin D. In the UK we have a bit of a problem with that, in that the sun is generally in short supply. In a normal year, vitamin D is not available to us between around the end of September and the beginning of May. It was thought that during the summer months we would accrue enough vitamin D to see us through winter. We now know this isn’t happening well enough. Modern life has got in the way, we don’t make vitamin D when the sun has to shine through glass, through clothing, through sunscreen, if it’s cloudy or polluted. We spend a lot of time indoors. Skin colour is also a barrier to our bodies making vitamin D. The darker your skin, the longer it will take you to make vitamin D, with some research suggesting a 3, 10 times longer period of exposure to achieve the same vitamin D exposure as a light-skinned person. Some very light skinned people are not off the hook as they tend to cover up in the sun with clothing or sunscreen to prevent burning. Some women are covered for cultural or religious reasons. Some people now just cover up as they are worried about the effects of ageing or skin cancer. Also, some people cannot get out as much as they would like due to disability or frailty.

Vitamin D is found in oily fish, eggs and fortified foods such as cereals and margarine. In the UK, milk is not a good source of vitamin D as it is not fortified.

It is estimated that we cannot eat enough foods containing vitamin D to become sufficient. A German study suggests that less than 10% of vitamin D requirement is met through foods (Sichert-Hellert et al 2006). It is also advised that girls and women of childbearing age, do not eat more than 2 portions of oily fish a week due to the potential pollutants in the fish.

From about late March/early April to the end of September, the majority of people should be able to make all the vitamin D they need from sunlight on their skin.

Children from the age of 1 year and adults need 10 micrograms of vitamin D a day. This includes pregnant and breastfeeding women, and people at risk of vitamin D deficiency.

Babies up to the age of 1 year need 8.5 to 10 micrograms of vitamin D a day.

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.

Vitamin D in supplement form can build up in your body and be toxic in large amounts, so do not exceed the amount you have been advised to take by your health professional. This is not the case with vitamin D obtained from the sun as your body can deal with any excess when obtained this way.

Some women are surprised to hear that breast milk is not a good source of vitamin D. Before saying more, breast milk is, of course, the best food for baby, bringing many health benefits to both baby and mum, but that doesn’t mean we should ignore the evidence.

Human milk contains only 15 – 50 IU/L vitamin D, with an average of 25 IU/L, (0.62mcg), which is not sufficient to meet the requirements of the human infant (Gartner et al 2003, Callaghan et al 2006, Leerbeck et al 1980).

The reason for this is the same as we discussed above, modern life! We no longer live outdoors, semi-naked, without buildings or cars or pollution. In fact, we don’t even have to go back that far, many people today don’t even go out for a walk, children don’t play in the street, babies are covered completely in their pushchairs as if they would vapourise if a ray of light touched them and many people do not go out without covering themselves in sunscreen.

Of course, we have to be sensible in the sun, neither you or your children should burn in the sun, but we do need some exposure, during summer months, during a hot part of the day, for 10 minutes or so on a reasonable part of our arms, legs or body, (face and hands alone are not enough). If you are fair skinned you can have two or three shorter exposures to the sun in one day, you don’t need to burn. Be more careful when you go abroad to a hot country. Babies should not be exposed to the sun and you should follow the supplement advice given to you by your midwife, health visitor or family doctor. However, they don’t need to be kept in a dark place, just sensible precautions.

For a list of useful contact details for The Portland Hospital, please click HERE.