Should I be taking a vitamin D supplement?

Those of us who live in the UK and have darker skin need longer exposure to summer sunlight to make the same amount of vitamin D as people with lighter skin - we are therefore at greater risk of vitamin D deficiency. 

Sunlight certainly wasn’t in short supply last summer, but this matters not, if one tends to avoid the sun or uses sunscreen every time when stepping into the rays. It would be sensible for most of us, regardless of skin colour, to take a vitamin D supplement between October and March if we don't get enough exposure to sunlight during April-September
 
Why is it important to have good vitamin D status?
 
Rickets in children is a well-known consequence of vitamin D deficiency.  Adults who have vitamin D deficiency may experience osteomalacia, a condition in which bones are more likely to fracture – due to poor calcification.  

Vitamin D is also needed by other tissues in our body, and this includes our brain.  Some studies link low vitamin D levels to depression – but the link might be explained by the likelihood that people who feel low are less likely to go out.  

​A particularly important role of vitamin D at this time of the year is that of supporting the immune system in keeping us well.  There is some evidence that having good vitamin D status offers a degree of protection against respiratory infections - might vitamin D help protect against COVID-19?
 
What are the best food sources of vitamin D?
 
Getting enough exposure to summer sun is the best way to build-up our vitamin D stores to maintain vitamin D sufficiency through winter months. 
 
The only naturally-rich food sources of vitamin D are oily fish (around 200IU - 600IU vitamin D per 140g serving) and egg (50IU - 150IU per egg). Dietary information resources often cite red meat (4IU - 40IU of vitamin D per 100g) and fortified margarine (around 15IU vitamin D per teaspoon) as sources of vitamin D, but each of these make only a very small contribution to our daily intake of vitamin D.  
 
Some foods are fortified with vitamin D and these include some brands of products, such as yogurt, breakfast cereal and plant-based alternatives to milk.
 
How else can we get vitamin D?

Inadequate intake of food sources of vitamin D (and this is not diffiult to do!) and insufficient exposure to the summer sun will, of course, lead to vitamin D deficiency – around 23% of adults have vitamin D deficiency, defined as bood 25OHD level below 25nmol/L. 

Vitamin D supplements are inexpensive and an easy way to boost vitamin D stores during winter months. They are available as tablets, oral sprays and drops and all are effective at increasing blood levels of vitamin D.
 
How much vitamin D do we need?

A daily serving of oily fish would get us close to (or exceed) the RNI for vitamin D (400IU = 10ug a day), but for most us, consuming oily fish on a daily basis is very unlikely, unless you’re a dolphin! The RNI for vitamin D is considerably lower than the dose of vitamin D (around 30ug a day) required by sun-avoiders if they are to achieve vitamin D sufficiency – a serum 25OHD concentration above 50nmol/L).
 
Most of us can meet our vitamin D requirement by taking a daily supplement providing 1000-2000IU (25-50ug) vitamin D - taking up to 4000IU (100ug) vitamin D a day is safe.
 
Click here for slides from the drop-in meeting of Aplos All-Stars. 

Tony Hirving
Dietitian                                       ​