King's College London

Vitamin D, which is vital for bone health, is produced by the skin in response to ultraviolet radiation (UVR) from sunlight. However, as well as being the primary source of vitamin D, UVR is a major cause of a skin cancer, the UK’s most common type of cancer.

In recent years, global concern about vitamin D deficiency has fuelled debates on how best to achieve healthy levels of vitamin D, known as vitamin D sufficiency, while simultaneously limiting the risk of skin cancer. Concerns have been raised that sun protection methods, including sunscreen use, may be contributing to vitamin D deficiency.

Now, researchers from King's have found that use of sunscreen does not impact on vitamin D status in the majority of people.

In their study, participants were split into four groups. The participants, apart from those in the control group, then went on a week-long holiday to an area with a very high UV index.

Twenty people received a broad spectrum* sunscreen with a Sun Protection Factor (SPF) of 15, offering UVB protection and high UVA protection. Twenty people received a non-broad spectrum sunscreen, also SPF 15 but with low UVA protection. These two groups were told how to use their sunscreens correctly, so as to achieve the labelled SPF. In contrast, 22 people used their own sunscreen with no instructions on how to apply it, and 17 people formed a control group who remained in Poland.

Blood (serum) samples were taken from participants 24 hours before and 24 to 48 hours after the holiday.

SPF 15 sunscreens applied at sufficient thickness to inhibit sunburn allowed a highly significant improvement of vitamin D levels. Furthermore, the broad spectrum sunscreen enabled higher vitamin D synthesis than a low UVA protective sunscreen, possibly because the former, due to its composition, transmits more a little more UVB than the latter.  The people who used their own sunscreens, also had significant vitamin D synthesis, but they all had sunburn.  This was almost certainly because they did not use their sunscreens correctly. During the same period, the control group has a slight decline in vitamin D.

Lead author, Professor Antony Young said: “Sunlight is the main source of vitamin D. Sunscreens can prevent sunburn and skin cancer, but there has been a lot of uncertainty about the effects of sunscreens on vitamin D.

“Our study, during a week of perfect weather in Tenerife, showed that sunscreens, even when used optimally to prevent sunburn, allowed excellent vitamin D synthesis.”

The full study is available online.

* Sunscreens that provide a balance of UVA and UVB protection are called ‘broad spectrum’, and these are generally recommended by medical experts.