Mr Muholan Kanapathy and Professor Ash Mosahebi discuss the conflicting advice surrounding sunscreen and vitamin D
As we well know, overexposure to ultraviolet (UV) radiation is a major risk factor for skin cancer. Consequently, strict UV protection by using sunscreens and other measures form the basis of most skin cancer prevention campaigns. However, as at least 80% of the human body’s need of vitamin D is synthesised in the skin by the action of solar UV rays,1 particularly the ultraviolet B (UVB) radiation, strict UV protection is claimed by some studies to promote vitamin D deficiency.2,3
Communicating the risks and benefits of sunlight exposure to patients can be challenging. In addition, many practitioners have differing opinions as to whether sunscreen affects vitamin D absorption to a point which could be detrimental to patients if sunscreen is or isn’t applied. On one hand, patients may have been advised to protect their skin from the sun to avoid skin cancer, while on the other hand, they may have been advised by aesthetic practitioners or their GP to expose themselves to sunlight to ensure that they get enough vitamin D. This conflicting advice is an issue and could be contributing towards conditions such as melanoma and vitamin D deficiency. For aesthetic practitioners, this is an important concern, as they regularly advise patients on how to protect and nourish their skin.
The latest National Institute for Health and Care Excellence (NICE) guidelines on the risks and benefits of sunlight exposure mention the need for protecting skin against UVA and UVB by applying sunscreen, but it does not address the effect of sunscreen on vitamin D absorption.1 The NICE committee expert testimony, which advises on these guidelines, however, confirmed that frequent, liberal use of high-protection sunscreen may prevent vitamin D synthesis, (this was not included in the guidelines) although the committee claim this is usually only true under research conditions and unlikely the case in practice.1 This is because people may inadvertently miss some areas of skin when they apply sunscreen and also tend to apply much less sunscreen than the manufacturer’s recommended amount.
Practitioners need to explain to patients that controlled and balanced exposure to UV with the use of sunscreen is essential to avoid photoageing and cancer risk, without unduly raising the risk of vitamin D deficiency
A study suggested sunscreen users customarily apply half or less of the amount of product stipulated by the Food and Drug Administration to generate the stated level of protection (2mg/cm2) and hence achieve far less protection.2 Therefore, it is our belief that sunscreen use has little impact on vitamin D absorption.
Nevertheless, there are many practitioners that believe sunscreen-use does severely impact on vitamin D absorption, this could be because an SPF 30, when properly applied, absorbs about 97.5% of UVB. The unintended consequence is that an SPF of 30 reduces the capacity of the skin to produce vitamin D by 97.5%.4 However, they may be unaware that the majority of people do not use sunscreen as recommended. This enforces the need for more education to be available on ensuring stable vitamin D levels through other means.
The optimal frequency and duration of sun exposure for the best ratio of benefit to risk depends on a range of biological, environmental and behavioural factors, but this must be communicated more clearly with patients. Practitioners need to explain to patients that controlled and balanced exposure to UV with the use of sunscreen is essential to avoid photoageing and cancer risk, without unduly raising the risk of vitamin D deficiency. This can be achieved by practitioners improving their knowledge and reading more research on vitamin D and sun exposure, before advising. We also believe the creation of more detailed guidelines for practitioners, as well as guidelines on application techniques of sunscreen are needed.
Regardless of one’s complexion or extent of UV exposure, daily oral vitamin D supplementation can compensate for lack of cutaneous vitamin D photosynthesis, and this should also be recommended.2 Patients can be informed that vitamin D can also be obtained from natural dietary sources and supplementation, such as oily fish like mackerel, salmon and sardines, as well as fortified margarine, cereals and egg yolks. In fact, the recent NICE guidelines state that it is not possible to get enough vitamin D from sunlight between October and March in the UK, emphasising the need for supplementation.1 The Department of Health already recommends supplementation (10mg of vitamin D a day) for pregnant and breastfeeding women, young children, older people and those at risk because of low sun exposure.5
Sun exposure is the main source of vitamin D, but excessive sun exposure is the main cause of skin cancer.1 Healthcare practitioners should communicate the importance of maintaining balance to protect skin from photoageing and cancer without resulting in vitamin D deficiency to the best of their ability, utilising as much research and clinical studies as they can. For those patients who are concerned about vitamin D deficiency, practitioners should advise them on alternative ways to ensure stable levels, such as dietary sources and supplements.
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