UK dermatologist explains the facts on vitamin D and sun exposure

Jun 16 2015

Sometimes it can be hard to weigh up the benefits of vitamin D versus sun exposure. We talk to Dr Anjali Mahto, Consultant Dermatologist & British Skin Foundation Spokesperson who explains.

Dr Anjali Mahto

“Vitamin D is essential for bone health and low levels can be linked to rickets in children. Whilst sun exposure is the main source of vitamin D, this needs to be balanced against the fact that sun exposure is also the main cause of skin cancer. The rates of skin cancer continue to rise in the UK since the mid-1970s.”

So how much time do we need to spend outside to get enough Vitamin D?

There is a unified view that the time to make vitamin D is short, and less than the amount of time needed for skin to become red and subsequently, burn. UK dermatologists recommend that regularly going outside for a few minutes around the middle of the day without sunscreen should be enough. Individuals need to recognize their own skin to get some idea how long they can spend outdoors without burning. For most people, everyday casual exposure to sunlight in the summer should be enough to produce adequate vitamin D.

Aside from this, it is important to practice sun safety measures to ensure that skin does not burn. Broad-spectrum sunscreen that offers protection against UVA and UVB that is at least SPF 30 is recommended.

How much sun is actually needed for the body to absorb the vitamin D?

This is a much more difficult question to answer as there is a complex interplay between environmental, personal, and physical factors and varies between individuals.

UVB in sunlight is required for vitamin D production and this is greatest around noon and during the summer. Dark skin requires more sunshine to produce adequate vitamin D compared to fair skin. Certain groups are more likely to be vitamin D deficient including the elderly, pregnant women, those who wear whole-body coverings, skin cancer patients, and infants born to mothers that are vitamin D deficient.

However, several minutes of sunshine in the spring and summer months at doses of UV below that which will cause sunburn should be enough to produce sufficient levels of vitamin In the UK, during winter, there is not enough UV to make vitamin However, if a sufficient supply is made in the summer, tissue stores should be adequate to get through the winter months.

Blood levels of 25(OH)D (25 hydroxyvitamin D) are the best marker for vitamin D status in the body. There is no accepted optimal level, but values below 12.5-25 nmol/L are agreed to be deficient. Vitamin D made in the skin is under tight homeostatic regulation and excess amounts are converted into inert substances. This is potentially not the case for dietary supplements, therefore these are not recommended for the general population, due to the risk of vitamin D building up to high levels.

So what about sunburn & children?

Whilst ensuring that children get enough sunshine to produce vitamin D, it is important that skin does not redden or burn. Sunburn is a sign of DNA damage to skin cells as a result of UV radiation. It is commoner in children than in adults so care needs to be taken to protect young skin. Data suggests that 5 or more sunburns in youth can increase lifetime melanoma risk by up to 80% and this risk should not be taken lightly.